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Dewar R, Hölttä T, Salmon Y. Exploring optimal stomatal control under alternative hypotheses for the regulation of plant sources and sinks. THE NEW PHYTOLOGIST 2022; 233:639-654. [PMID: 34637543 DOI: 10.1111/nph.17795] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/13/2021] [Accepted: 09/19/2021] [Indexed: 06/13/2023]
Abstract
Experimental evidence that nonstomatal limitations to photosynthesis (NSLs) correlate with leaf sugar and/or leaf water status suggests the possibility that stomata adjust to maximise photosynthesis through a trade-off between leaf CO2 supply and NSLs, potentially involving source-sink interactions. However, the mechanisms regulating NSLs and sink strength, as well as their implications for stomatal control, remain uncertain. We used an analytically solvable model to explore optimal stomatal control under alternative hypotheses for source and sink regulation. We assumed that either leaf sugar concentration or leaf water potential regulates NSLs, and that either phloem turgor pressure or phloem sugar concentration regulates sink phloem unloading. All hypotheses led to realistic stomatal responses to light, CO2 and air humidity, including conservative behaviour for the intercellular-to-atmospheric CO2 concentration ratio. Sugar-regulated and water-regulated NSLs are distinguished by the presence/absence of a stomatal closure response to changing sink strength. Turgor-regulated and sugar-regulated phloem unloading are distinguished by the presence/absence of stomatal closure under drought and avoidance/occurrence of negative phloem turgor. Results from girdling and drought experiments on Pinus sylvestris, Betula pendula, Populus tremula and Picea abies saplings are consistent with optimal stomatal control under sugar-regulated NSLs and turgor-regulated unloading. Our analytical results provide a simple representation of stomatal responses to above-ground and below-ground environmental factors and sink activity.
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Affiliation(s)
- Roderick Dewar
- Faculty of Science, Institute for Atmospheric and Earth System Research/Physics, University of Helsinki, PO Box 68, Gustaf Hällströmin katu 2b, Helsinki, 00014, Finland
- Plant Sciences Division, Research School of Biology, The Australian National University, Canberra, ACT, 2601, Australia
| | - Teemu Hölttä
- Faculty of Agriculture and Forestry, Institute for Atmospheric and Earth System Research/Forest Sciences, University of Helsinki, PO Box 27, Latokartanonkaari 7, Helsinki, 00014, Finland
| | - Yann Salmon
- Faculty of Science, Institute for Atmospheric and Earth System Research/Physics, University of Helsinki, PO Box 68, Gustaf Hällströmin katu 2b, Helsinki, 00014, Finland
- Faculty of Agriculture and Forestry, Institute for Atmospheric and Earth System Research/Forest Sciences, University of Helsinki, PO Box 27, Latokartanonkaari 7, Helsinki, 00014, Finland
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Cheng JS, Duan W, Tang XL, Zhang YG, Li B, Wang YJ, Yang CX, Song ZZ, Wang LJ, Yang J, Yu Y, Sun XB, Liang MX, Liang ZC, Zhang HX. Low sink demand caused net photosynthetic rate decrease is closely related to the irrecoverable damage of oxygen-releasing complex and electron receptor in peach trees. JOURNAL OF PLANT PHYSIOLOGY 2021; 266:153510. [PMID: 34521019 DOI: 10.1016/j.jplph.2021.153510] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/03/2021] [Revised: 08/31/2021] [Accepted: 08/31/2021] [Indexed: 06/13/2023]
Abstract
Source sink balance is one of the major determinants of carbon partitioning in plants. However, its effects on photosynthesis in fruit trees are largely unknown. In this work, the effects of low sink demand on net photosynthetic rate (Pn) and chlorophyll fluorescence after fruit removal (-fruit) in peach (Prunus persica (L.) Batsch cv. 'Zaojiubao') trees were investigated. The stepwise energy flow through photosystem II (PSII) at the reaction center (RC) was analyzed with quantitative analyses of fluorescence transient, also called JIP-test. We found that Pn was significantly lower and closely correlated to the leaf stomatal conductance (Gs) of -fruit trees than that of fruit retained (+fruit) trees. Leaf temperature (Tleaf) of -fruit trees was remarkably higher than that of +fruit trees. Day-time-period assays of chlorophyll (Chl) fluorescence revealed that, in the leaves of -fruit trees, the fluorescence parameters, such as NPQ (non-photochemical quenching coefficient) and ΦD0 (maximum quantum yield of non-photochemical de-excitation), decreased in the morning and recovered to the normal level in the afternoon, whereas other parameters, such as ΦE0 (quantum yield for electron transport at t = 0), Ψ0 (probability that a trapped exciton moves an electron to QA pool), F0 (minimum fluorescence, when all PSII RCs are open) and Wk (relative variable fluorescence at 300 μs of the chlorophyll fluorescence transient), did not. These results suggest that OEC complex and QA pool were irreversibly affected by low sink demand, whereas light harvest antenna and PSII potential efficiency retained a strong ability to recover.
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Affiliation(s)
- Jie-Shan Cheng
- The Engineering Research Institute of Agriculture and Forestry, Ludong University, 186 Hongqizhong Road, Yantai, 264025, China; The Key Laboratory of Molecular Module-Based Breeding of High Yield and Abiotic Resistant Plants in the Universities of Shandong (Ludong University), Institute for Advanced Study of Coastal Ecology, Ludong University, 186 Hongqizhong Road, Yantai, 264025, China
| | - Wei Duan
- Institute of Botany, Chinese Academy of Sciences, 20 Nanxincun, Xiangshan Road, Beijing, 100093, China
| | - Xiao-Li Tang
- The Engineering Research Institute of Agriculture and Forestry, Ludong University, 186 Hongqizhong Road, Yantai, 264025, China; The Key Laboratory of Molecular Module-Based Breeding of High Yield and Abiotic Resistant Plants in the Universities of Shandong (Ludong University), Institute for Advanced Study of Coastal Ecology, Ludong University, 186 Hongqizhong Road, Yantai, 264025, China
| | - Yao-Guang Zhang
- College of Art, Ludong University, 186 Hongqizhong Road, Yantai, 264025, China
| | - Bei Li
- The Engineering Research Institute of Agriculture and Forestry, Ludong University, 186 Hongqizhong Road, Yantai, 264025, China; The Key Laboratory of Molecular Module-Based Breeding of High Yield and Abiotic Resistant Plants in the Universities of Shandong (Ludong University), Institute for Advanced Study of Coastal Ecology, Ludong University, 186 Hongqizhong Road, Yantai, 264025, China
| | - Yi-Ju Wang
- Yantai Academy of Agricultural Science, 26 Gangchengxi Road, Yantai, 265500, China
| | - Chun-Xiang Yang
- Institute of Botany, Chinese Academy of Sciences, 20 Nanxincun, Xiangshan Road, Beijing, 100093, China
| | - Zhi-Zhong Song
- The Engineering Research Institute of Agriculture and Forestry, Ludong University, 186 Hongqizhong Road, Yantai, 264025, China; The Key Laboratory of Molecular Module-Based Breeding of High Yield and Abiotic Resistant Plants in the Universities of Shandong (Ludong University), Institute for Advanced Study of Coastal Ecology, Ludong University, 186 Hongqizhong Road, Yantai, 264025, China
| | - Li-Jun Wang
- Institute of Botany, Chinese Academy of Sciences, 20 Nanxincun, Xiangshan Road, Beijing, 100093, China
| | - Jun Yang
- Institute of Botany, Chinese Academy of Sciences, 20 Nanxincun, Xiangshan Road, Beijing, 100093, China
| | - Yan Yu
- Yantai Institute, China Agricultural University, 2006 Binhaizhong Road, Yantai, 264670, China
| | - Xiu-Bo Sun
- Yantai Institute, China Agricultural University, 2006 Binhaizhong Road, Yantai, 264670, China
| | - Mei-Xia Liang
- The Engineering Research Institute of Agriculture and Forestry, Ludong University, 186 Hongqizhong Road, Yantai, 264025, China; The Key Laboratory of Molecular Module-Based Breeding of High Yield and Abiotic Resistant Plants in the Universities of Shandong (Ludong University), Institute for Advanced Study of Coastal Ecology, Ludong University, 186 Hongqizhong Road, Yantai, 264025, China; College of Agriculture, Ludong University, 186 Hongqizhong Road, Yantai, 264025, China
| | - Zhen-Chang Liang
- Institute of Botany, Chinese Academy of Sciences, 20 Nanxincun, Xiangshan Road, Beijing, 100093, China.
| | - Hong-Xia Zhang
- The Engineering Research Institute of Agriculture and Forestry, Ludong University, 186 Hongqizhong Road, Yantai, 264025, China; The Key Laboratory of Molecular Module-Based Breeding of High Yield and Abiotic Resistant Plants in the Universities of Shandong (Ludong University), Institute for Advanced Study of Coastal Ecology, Ludong University, 186 Hongqizhong Road, Yantai, 264025, China.
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Lo Piccolo E, Landi M, Massai R, Remorini D, Guidi L. Girled-induced anthocyanin accumulation in red-leafed Prunus cerasifera: Effect on photosynthesis, photoprotection and sugar metabolism. PLANT SCIENCE : AN INTERNATIONAL JOURNAL OF EXPERIMENTAL PLANT BIOLOGY 2020; 294:110456. [PMID: 32234225 DOI: 10.1016/j.plantsci.2020.110456] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/28/2019] [Revised: 02/18/2020] [Accepted: 02/20/2020] [Indexed: 05/20/2023]
Abstract
The feedback regulation of photosynthesis depends on the cooperation of multiple signals, including sugars. Herein, the effect of shoot girdling was monitored on a daily basis for three days in green- and red-leafed Prunus cerasifera plants (GLP and RLP, respectively). The effect of anthocyanin presence was investigated in terms of photosynthesis, sugar metabolism and photoprotection. Net photosynthesis (A390) and stomatal conductance were reduced on the first day at 12:00 only in the girdled GLP (29 and 33 %, respectively). Moreover, the girdled GLP displayed at 12:00 higher sucrose, glucose and fructose concentrations than control leaves. Conversely, girdled RLP showed the first reduction of A390 at 18:00, with no significant differences at 12:00 in sucrose and glucose concentrations. The increased biosynthesis of anthocyanins that was only detected in girdled RLP contributed to lowering the accumulation of hexoses. Overall, these results revealed a sugar-buffering role exerted by anthocyanins that positively influence the feedback regulation of photosynthesis. Moreover, non-photochemical quenching, namely pNPQ, revealed the ability of anthocyanins to photoprotect photosystem II from supernumerary photons reaching the chloroplast, whose function was compromised by girdling. The present study provides a starting point to understand the possible link between photosynthesis regulation through sugar signalling and anthocyanin upregulation.
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Affiliation(s)
- Ermes Lo Piccolo
- Department of Agriculture, Food and Environment, University of Pisa, Via del Borghetto, 80, 56124, Pisa, Italy
| | - Marco Landi
- Department of Agriculture, Food and Environment, University of Pisa, Via del Borghetto, 80, 56124, Pisa, Italy; Interdepartmental Research Center Nutrafood "Nutraceuticals and Food for Health", University of Pisa, Via del Borghetto, 80, 56124, Pisa, Italy.
| | - Rossano Massai
- Department of Agriculture, Food and Environment, University of Pisa, Via del Borghetto, 80, 56124, Pisa, Italy; Interdepartmental Research Center Nutrafood "Nutraceuticals and Food for Health", University of Pisa, Via del Borghetto, 80, 56124, Pisa, Italy
| | - Damiano Remorini
- Department of Agriculture, Food and Environment, University of Pisa, Via del Borghetto, 80, 56124, Pisa, Italy; Interdepartmental Research Center Nutrafood "Nutraceuticals and Food for Health", University of Pisa, Via del Borghetto, 80, 56124, Pisa, Italy
| | - Lucia Guidi
- Department of Agriculture, Food and Environment, University of Pisa, Via del Borghetto, 80, 56124, Pisa, Italy; Interdepartmental Research Center Nutrafood "Nutraceuticals and Food for Health", University of Pisa, Via del Borghetto, 80, 56124, Pisa, Italy
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Oberhuber W, Gruber A, Lethaus G, Winkler A, Wieser G. Stem girdling indicates prioritized carbon allocation to the root system at the expense of radial stem growth in Norway spruce under drought conditions. ENVIRONMENTAL AND EXPERIMENTAL BOTANY 2017; 138:109-118. [PMID: 28392608 PMCID: PMC5381714 DOI: 10.1016/j.envexpbot.2017.03.004] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/17/2023]
Abstract
The early culmination of maximum radial growth (RG) in late spring has been found in several coniferous species in a dry inner Alpine environment. We hypothesized that an early decrease in RG is an adaptation to cope with drought stress, which might require an early switch of carbon (C) allocation to belowground organs. To test this hypothesis, we experimentally subjected six-year-old Norway spruce saplings (tree height: 1.35 m; n = 80 trees) to two levels of soil water availability (watered versus drought conditions) and manipulated tree C status by physically blocking phloem transport at three girdling dates (GD). The influence of C availability and drought on tree growth (radial and shoot growth; root biomass) in response to girdling was analyzed in both treatments. Non-structural carbohydrates (NSCs, soluble sugars and starch) were measured in the stem, root and current leader to evaluate changes in tree C status due to girdling. The main finding was a significant increase in RG of the girdled trees compared to the controls above the girdling zone (UZ). At all girdling dates the RG increase was significantly more intense in the drought-stressed compared with watered trees (c. 3.3 and 1.9-fold higher compared with controls in the drought-stressed and watered trees, respectively), most likely indicating that an early switch of C allocation to belowground occurs as an adaptation to maintain tree water status under drought conditions. Reactivation of the cambium after the cessation of its regular activity was detected in UZ in drought-stressed trees, while below the girdling zone no xylem formation was found and the NSC content was strikingly reduced. Irrespective of water availability, girdling before growth onset significantly reduced the progression of bud break (P < 0.05) and the length of the current leader shoot by -47% (P < 0.01) indicating a reduction in xylem hydraulic conductance, which was corroborated by significantly reduced xylem sap flow (P < 0.001). Based on our findings, we conclude that during the growing season drought stress prioritizes an early switch of C allocation to the root system as an adaptation to maintain adequate tree water status in drought-prone environments.
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Affiliation(s)
- Walter Oberhuber
- Institute of Botany, Leopold-Franzens-University of Innsbruck, Sternwartestrasse 15, A-6020 Innsbruck, Austria
| | - Andreas Gruber
- Institute of Botany, Leopold-Franzens-University of Innsbruck, Sternwartestrasse 15, A-6020 Innsbruck, Austria
| | - Gina Lethaus
- Institute of Botany, Leopold-Franzens-University of Innsbruck, Sternwartestrasse 15, A-6020 Innsbruck, Austria
| | - Andrea Winkler
- Institute of Botany, Leopold-Franzens-University of Innsbruck, Sternwartestrasse 15, A-6020 Innsbruck, Austria
| | - Gerhard Wieser
- Department of Alpine Timberline Ecophysiology, Federal Research and Training Centre for Forests, Natural Hazards and Landscape (BFW), Rennweg 1, A-6020 Innsbruck, Austria
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Asao S, Ryan MG. Carbohydrate regulation of photosynthesis and respiration from branch girdling in four species of wet tropical rain forest trees. TREE PHYSIOLOGY 2015; 35:608-620. [PMID: 25870320 DOI: 10.1093/treephys/tpv025] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/30/2014] [Accepted: 02/26/2015] [Indexed: 06/04/2023]
Abstract
How trees sense source-sink carbon balance remains unclear. One potential mechanism is a feedback from non-structural carbohydrates regulating photosynthesis and removing excess as waste respiration when the balance of photosynthesis against growth and metabolic activity changes. We tested this carbohydrate regulation of photosynthesis and respiration using branch girdling in four tree species in a wet tropical rainforest in Costa Rica. Because girdling severs phloem to stop carbohydrate export while leaving xylem intact to allow photosynthesis, we expected carbohydrates to accumulate in leaves to simulate a carbon imbalance. We varied girdling intensity by removing phloem in increments of one-quarter of the circumference (zero, one--quarter, half, three-quarters, full) and surrounded a target branch with fully girdled ones to create a gradient in leaf carbohydrate content. Light saturated photosynthesis rate was measured in situ, and foliar respiration rate and leaf carbohydrate content were measured after destructive harvest at the end of the treatment. Girdling intensity created no consistent or strong responses in leaf carbohydrates. Glucose and fructose slightly increased in all species by 3.4% per one-quarter girdle, total carbon content and leaf mass per area increased only in one species by 5.4 and 5.5% per one-quarter girdle, and starch did not change. Only full girdling lowered photosynthesis in three of four species by 59-69%, but the decrease in photosynthesis was unrelated to the increase in glucose and fructose content. Girdling did not affect respiration. The results suggest that leaf carbohydrate content remains relatively constant under carbon imbalance, and any changes are unlikely to regulate photosynthesis or respiration. Because girdling also stops the export of hormones and reactive oxygen species, girdling may induce physiological changes unrelated to carbohydrate accumulation and may not be an effective method to study carbohydrate feedback in leaves. In three species, removal of three-quarters of phloem area did not cause leaf carbohydrates to accumulate nor did it change photosynthesis or respiration, suggesting that phloem transport is flexible and transport rate per unit phloem can rapidly increase under an increase in carbohydrate supply relative to phloem area. Leaf carbohydrate content thus may be decoupled from whole plant carbon balance by phloem transport in some species, and carbohydrate regulation of photosynthesis and respiration may not be as common in trees as previous girdling studies suggest. Further studies in carbohydrate regulation should avoid using girdling as girdling can decrease photosynthesis through unintended means without the tested mechanisms of accumulating leaf carbohydrates.
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Affiliation(s)
- Shinichi Asao
- Graduate Degree Program in Ecology, Colorado State University, Fort Collins, CO 80523-1401, USA Natural Resources Ecology Laboratory, Colorado State University, Fort Collins, CO 80523-1499, USA
| | - Michael G Ryan
- Natural Resources Ecology Laboratory, Colorado State University, Fort Collins, CO 80523-1499, USA Emeritus, USDA Forest Service, Rocky Mountain Research Station, 240 West Prospect Street, Fort Collins, CO 80526, USA
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Tombesi S, Day KR, Johnson RS, Phene R, DeJong TM. Vigour reduction in girdled peach trees is related to lower midday stem water potentials. FUNCTIONAL PLANT BIOLOGY : FPB 2014; 41:1336-1341. [PMID: 32481081 DOI: 10.1071/fp14089] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/18/2014] [Accepted: 06/23/2014] [Indexed: 06/11/2023]
Abstract
Stem or trunk girdling is a technique used in physiological studies and in horticultural practice for interrupting carbon flow through the phloem to other parts of the plant without influencing water flow in the xylem. Trunk girdling in peaches is practiced primarily to stimulate fruit growth but it also tends to decrease shoot vigour for a period of time after girdling. Water flow through the trunk or branches of peach trees is thought to be primarily dependent on the most recently formed ring of xylem and vegetative growth is closely related to stem water potential and stem hydraulic conductance. The aim of the present work was to determine whether vigour reduction due to girdling was correlated with a reduction in midday stem water potential during the period of time between girdling and the subsequent healing of stem tissue. 'Springcrest' peach trees were girdled on two different dates. Fruit yield and size, water sprout growth, proleptic shoot growth and stem water potential were measured. Early and late girdled trees yielded larger fruits and fewer and shorter water sprouts in comparison with control trees. Midday stem water potential declined significantly after girdling and gradually recovered until the time of fruit harvest. These results suggest that the vigour reduction of girdled trees is related to a decrease of midday stem water potential caused by girdling. Early tree girdling increased the reduction in midday stem water potential and shoot growth compared with the later girdling treatment. These results point out that even though girdling only removes bark and phloem tissue it can apparently affect water flow in xylem.
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Affiliation(s)
- Sergio Tombesi
- Dipartimento di Scienze Agrarie, Alimentari e Ambientali, Università degli Studi di Perugia, Borgo XX giugno 74, 06121, Perugia, Italy
| | - Kevin R Day
- Department of Plant Sciences, University of California, One Shields Avenue, Davis, CA 95616, USA
| | - R Scott Johnson
- Department of Plant Sciences, University of California, One Shields Avenue, Davis, CA 95616, USA
| | - Rebecca Phene
- Department of Plant Sciences, University of California, One Shields Avenue, Davis, CA 95616, USA
| | - Theodore M DeJong
- Department of Plant Sciences, University of California, One Shields Avenue, Davis, CA 95616, USA
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Fanwoua J, Bairam E, Delaire M, Buck-Sorlin G. The role of branch architecture in assimilate production and partitioning: the example of apple (Malus domestica). FRONTIERS IN PLANT SCIENCE 2014; 5:338. [PMID: 25071813 PMCID: PMC4089354 DOI: 10.3389/fpls.2014.00338] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/31/2014] [Accepted: 06/25/2014] [Indexed: 05/21/2023]
Abstract
Understanding the role of branch architecture in carbon production and allocation is essential to gain more insight into the complex process of assimilate partitioning in fruit trees. This mini review reports on the current knowledge of the role of branch architecture in carbohydrate production and partitioning in apple. The first-order carrier branch of apple illustrates the complexity of branch structure emerging from bud activity events and encountered in many fruit trees. Branch architecture influences carbon production by determining leaf exposure to light and by affecting leaf internal characteristics related to leaf photosynthetic capacity. The dynamics of assimilate partitioning between branch organs depends on the stage of development of sources and sinks. The sink strength of various branch organs and their relative positioning on the branch also affect partitioning. Vascular connections between branch organs determine major pathways for branch assimilate transport. We propose directions for employing a modeling approach to further elucidate the role of branch architecture on assimilate partitioning.
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Affiliation(s)
- Julienne Fanwoua
- *Correspondence: Julienne Fanwoua, UMR 1345 Institut de Recherche en Horticulture et Semences, AGROCAMPUS OUEST-Centre d’Angers, Institut National d’Horticulture et de Paysage 2 Rue André le Notre, 49045 Angers Cedex 01, France e-mail:
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Yan BF, Duan W, Liu GT, Xu HG, Wang LJ, Li SH. Response of bean (Vicia faba L.) plants to low sink demand by measuring the gas exchange rates and chlorophyll a fluorescence kinetics. PLoS One 2013; 8:e80770. [PMID: 24324626 PMCID: PMC3851463 DOI: 10.1371/journal.pone.0080770] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2013] [Accepted: 10/16/2013] [Indexed: 11/18/2022] Open
Abstract
Background The decline of photosynthesis in plants under low sink demand is well known. Previous studies focused on the relationship between stomatal conductance (gs) and net photosynthetic rate (Pn). These studies investigated the effect of changes in Photosystem II (PSII) function on the Pn decline under low sink demand. However, little is known about its effects on different limiting steps of electron transport chain in PSII under this condition. Methodology/Principal Finding Two-month-old bean plants were processed by removing pods and flowers (low sink demand). On the 1st day after low sink demand treatment, a decline of Pn was accompanied by a decrease in gs and internal-to-ambient CO2 concentration ratio (Ci/Ca). From the 3rd to 9th day, Pn and gs declined continuously while Ci/Ca ratio remained stable in the treatment. Moreover, these values were lower than that of control. Wk (a parameter reflecting the damage to oxygen evolving complex of the donor side of PSII) values in the treatment were significantly higher than their corresponding control values. However, RCQA (a parameter reflecting the number of active RCs per excited cross-section of PSII) values in the treatment were significantly lower than control from the 5th day. From the 11th to 21st day, Pn and gs of the treatment continued to decline and were lower than control. This was accompanied by a decrease of RCQA, and an increase of Wk. Furthermore, the quantum yield parameters φPo, φEo and ψEo in the treatment were lower than in control; however, Ci/Ca values in the treatment gradually increased and were significantly higher than control on the 21st day. Conclusions Stomatal limitation during the early stage, whereas a combination of stomatal and non-stomatal limitation during the middle stage might be responsible for the reduction of Pn under low sink demand. Non-stomatal limitation during the late stages after the removal of the sink of roots and pods may also cause Pn reduction. The non-stomatal limitation was associated with the inhibition of PSII electron transport chain. Our data suggests that the donor side of PSII was the most sensitive to low sink demand followed by the reaction center of PSII. The acceptor side of PSII may be the least sensitive.
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Affiliation(s)
- Bo-Fang Yan
- Beijing Key Laboratory of Grape Science and Enology and Key Laboratory of Plant Resources, Institute of Botany, the Chinese Academy of Sciences, Beijing, People’s Republic of China
- University of Chinese Academy of Sciences, Beijing, People’s Republic of China
| | - Wei Duan
- Beijing Key Laboratory of Grape Science and Enology and Key Laboratory of Plant Resources, Institute of Botany, the Chinese Academy of Sciences, Beijing, People’s Republic of China
| | - Guo-Tian Liu
- Beijing Key Laboratory of Grape Science and Enology and Key Laboratory of Plant Resources, Institute of Botany, the Chinese Academy of Sciences, Beijing, People’s Republic of China
- University of Chinese Academy of Sciences, Beijing, People’s Republic of China
| | - Hong-Guo Xu
- Beijing Key Laboratory of Grape Science and Enology and Key Laboratory of Plant Resources, Institute of Botany, the Chinese Academy of Sciences, Beijing, People’s Republic of China
| | - Li-Jun Wang
- Beijing Key Laboratory of Grape Science and Enology and Key Laboratory of Plant Resources, Institute of Botany, the Chinese Academy of Sciences, Beijing, People’s Republic of China
- * E-mail: (L-JW); (S-HL)
| | - Shao-Hua Li
- Beijing Key Laboratory of Grape Science and Enology and Key Laboratory of Plant Resources, Institute of Botany, the Chinese Academy of Sciences, Beijing, People’s Republic of China
- Key Laboratory of Plant Germplasm Enhancement and Specialty Agriculture, Wuhan Botanical Garden, the Chinese Academy of Sciences, Wuhan, People’s Republic of China
- * E-mail: (L-JW); (S-HL)
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Quentin AG, Close DC, Hennen LMHP, Pinkard EA. Down-regulation of photosynthesis following girdling, but contrasting effects on fruit set and retention, in two sweet cherry cultivars. PLANT PHYSIOLOGY AND BIOCHEMISTRY : PPB 2013; 73:359-367. [PMID: 24189522 DOI: 10.1016/j.plaphy.2013.10.014] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/02/2013] [Accepted: 10/10/2013] [Indexed: 06/02/2023]
Abstract
Sweet cherry (Prunus avium) trees were manipulated to analyse the contribution of soluble sugars to sink feedback down-regulation of leaf net CO2 assimilation rate (Anet) and fruit set and quality attributes. Total soluble sugar concentration and Anet were measured in the morning on fully expanded leaves of girdled branches in two sweet cherry cultivars, 'Kordia' and 'Sylvia' characterised typically by low and high crop load, respectively. Leaves on girdled trees had higher soluble sugar concentrations and reduced Anet than leaves on non-girdled trees. Moreover, RuBP carboxylation capacity of Rubisco (Vcmax) and triose-phosphate utilisation (TPU) were repressed in the girdled treatments, despite Jmax remaining unchanged; suggesting an impairment of photosynthetic capacity in response to the girdling treatment. Leaf Anet was negatively correlated to soluble sugars, suggesting a sink feedback regulatory control of photosynthesis. Although there were significantly less fruit set and retained in 'Kordia' than 'Sylvia'; girdling had contrasting effects in each cultivar. Girdling significantly increased fruit set and fruitlet retention in 'Sylvia' cultivar, but had no effect in 'Kordia' cultivar. We propose that low inherent sink demand for photoassimilates of 'Kordia' fruit could have contributed to the low fruit retention rate, since both non-girdled and girdled trees exhibited similar retention rate and that increases in foliar carbohydrates was observed above the girdle. In 'Sylvia' cultivar, the carbohydrate status may be a limiting factor for 'Sylvia' fruit, since girdling improved both fruit set and retention, and leaf soluble solids accumulation.
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Affiliation(s)
- A G Quentin
- Perennial Horticulture Centre, Tasmanian Institute of Agriculture, University of Tasmania, Private Bag 54, Hobart, Tasmania 7001 Australia; CSIRO Ecosystem Sciences, Private Bag 12, Hobart 7001, Australia.
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De Schepper V, De Swaef T, Bauweraerts I, Steppe K. Phloem transport: a review of mechanisms and controls. JOURNAL OF EXPERIMENTAL BOTANY 2013; 64:4839-50. [PMID: 24106290 DOI: 10.1093/jxb/ert302] [Citation(s) in RCA: 157] [Impact Index Per Article: 14.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/02/2023]
Abstract
It is generally believed that an osmotically generated pressure gradient drives the phloem mass flow. So far, this widely accepted Münch theory has required remarkably few adaptations, but the debate on alternative and additional hypotheses is still ongoing. Recently, a possible shortcoming of the Münch theory has been pointed out, suggesting that the Münch pressure flow is more suitable for herbs than for trees. Estimation of the phloem resistance indicates that a point might be reached in long sieve tubes where the pressure required to drive the Münch flow cannot be generated. Therefore, the relay hypothesis regained belief as it implies that the sieve tubes are shorter then the plant's axial axis. In the source phloem, three different loading strategies exist which probably result from evolutionary advantages. Passive diffusion seems to be the most primitive one, whereas active loading strategies substantially increase the growth potential. Along the transport phloem, a leakage-retrieval mechanism is observed. Appreciable amounts of carbohydrates are lost from the sieve tubes to feed the lateral sinks, while a part of these lost carbohydrates is subsequently reloaded into the sieve tubes. This mechanism is probably involved to buffer short-term irregularities in phloem turgor and gradient. In the long term, the mechanism controls the replenishment and remobilization of lateral stem storage tissues. As phloem of higher plants has multiple functions in plant development, reproduction, signalling, and growth, the fundamental understanding of the mechanisms behind phloem transport should be elucidated to increase our ability to influence plant growth and development.
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Affiliation(s)
- Veerle De Schepper
- Laboratory of Plant Ecology, Department of Applied Ecology and Environmental Biology, Faculty of Bioscience Engineering, Ghent University, Coupure Links 653, 9000 Ghent, Belgium
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Smith HM, Samach A. Constraints to obtaining consistent annual yields in perennial tree crops. I: Heavy fruit load dominates over vegetative growth. PLANT SCIENCE : AN INTERNATIONAL JOURNAL OF EXPERIMENTAL PLANT BIOLOGY 2013; 207:158-67. [PMID: 23602111 DOI: 10.1016/j.plantsci.2013.02.014] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/27/2012] [Revised: 02/20/2013] [Accepted: 02/23/2013] [Indexed: 05/08/2023]
Abstract
Farmers lack effective methods to achieve and maintain stable production from year to year in many commercial fruit crops. Annual fruit yield within a region often alternates between high and low fruit load and is termed alternate bearing. The underlying cause of alternate bearing is the negative impact of high fruit load on vegetative growth and next year's flowering. In this review, we emphasize common responses of diverse perennials to heavy crop load. We present botanical, ecological and horticultural perspectives on irregular bearing. The later part of this review focuses on understanding how high fruit load dominates over vegetative growth. We discuss sink strengths and putative mobile signals (hormones), perhaps seed-derived. We highlight gaps in current understanding of alternate bearing, and discuss new approaches to better understand fruit load dominance. Assuming the effect of high fruit load may be related to other mechanisms of sink partitioning, other forms of dominance are presented such as apical, first fruit and king fruit dominance. Dominance seems to be enforced, in independent cases through the establishment of a polar auxin transport system from the stronger sink. Once established this somehow perturbs the transport of auxin out of weaker sinks. Possibly, fruit derived auxin may alter the polar auxin transport system of the shoot to inhibit shoot growth.
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Affiliation(s)
- Harley M Smith
- CSIRO Plant Industry, Waite Campus, PO Box 350, Glen Osmond, South Australia 5064, Australia
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De Schepper V, Vanhaecke L, Steppe K. Localized stem chilling alters carbon processes in the adjacent stem and in source leaves. TREE PHYSIOLOGY 2011; 31:1194-1203. [PMID: 22001166 DOI: 10.1093/treephys/tpr099] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
Transport phloem is no longer associated with impermeable pipes, but is instead considered as a leaky system in which loss and retrieval mechanisms occur. Local stem chilling is often used to study these phenomena. In this study, 5-cm- lengths of stems of 3-year-old oak trees (Quercus robur L.) were locally chilled for 1 week to investigate whether observations at stem and leaf level can be explained by the leakage-retrieval mechanism. The chilling experiment was repeated three times across the growing season. Measurements were made of leaf photosynthesis, carbohydrate concentrations in leaves and bark, stem growth and maximum daily stem shrinkage. Across the growing season, a feedback inhibition in leaf photosynthesis was observed, causing increased dark respiration and starch concentration. This inhibition was attributed to the total phloem resistance which locally increased due to the cold temperatures. It is hypothesized that this higher phloem resistance increased the phloem pressure above the cold block up to the source leaves, inducing feedback inhibition. In addition, an increase in radial stem growth and carbohydrate concentration was observed above the cold block, while the opposite occurred below the block. These observations indicate that net lateral leakage of carbohydrates from the phloem was enhanced above the cold block and that translocation towards regions below the block decreased. This behaviour is probably also attributable to the higher phloem resistance. The chilling effects on radial stem growth and carbohydrate concentration were significant in the middle of the growing season, while they were not at the beginning and near the end of the growing season. Furthermore, maximum daily shrinkages were larger above the cold block during all chilling experiments, indicating an increased resistance in the xylem vessels, also generated by low temperatures. In conclusion, localized stem chilling altered multiple carbon processes in the source leaves and the main stem by changing hydraulic resistances.
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Affiliation(s)
- Veerle De Schepper
- Laboratory of Plant Ecology, Department of Applied Ecology and Environmental Biology, Faculty of Bioscience Engineering, Ghent University, Coupure Links 653, B-9000 Ghent, Belgium.
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De Schepper V, Steppe K. Tree girdling responses simulated by a water and carbon transport model. ANNALS OF BOTANY 2011; 108:1147-54. [PMID: 21478174 PMCID: PMC3189833 DOI: 10.1093/aob/mcr068] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/26/2010] [Accepted: 02/10/2011] [Indexed: 05/18/2023]
Abstract
BACKGROUND AND AIMS Girdling, or the removal of a strip of bark around a tree's outer circumference, is often used to study carbon relationships, as it triggers several carbon responses which seem to be interrelated. METHODS An existing plant model describing water and carbon transport in a tree was used to evaluate the mechanisms behind the girdling responses. Therefore, the (un)loading functions of the original model were adapted and became a function of the phloem turgor pressure. KEY RESULTS The adapted model successfully simulated the measured changes in stem growth induced by girdling. The model indicated that the key driving variables for the girdling responses were changes in turgor pressure due to local changes in sugar concentrations. Information about the local damage to the phloem system was transferred to the other plant parts (crown and roots) by a change in phloem pressure. After girdling, the loading rate was affected and corresponded to the experimentally observed feedback inhibition. In addition, the unloading rate decreased after girdling and even reversed in some instances. The model enabled continuous simulation of changes in starch content, although a slight underestimation was observed compared with measured values. CONCLUSIONS For the first time a mechanistic plant model enabled simulation of tree girdling responses, which have thus far only been experimentally observed and fragmentally reported in literature. The close agreement between measured and simulated data confirms the underlying mechanisms introduced in the model.
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Affiliation(s)
- Veerle De Schepper
- Laboratory of Plant Ecology, Department of Applied Ecology and Environmental Biology, Ghent University, Coupure links 653, B-9000 Ghent, Belgium.
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Fan PG, Li LS, Duan W, Li WD, Li SH. Photosynthesis of young apple trees in response to low sink demand under different air temperatures. TREE PHYSIOLOGY 2010; 30:313-25. [PMID: 20071359 DOI: 10.1093/treephys/tpp114] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/11/2023]
Abstract
Gas exchange, chlorophyll fluorescence, photosynthetic end products and related enzymes in source leaves in response to low sink demand after girdling to remove the root sink were assessed in young apple trees (Malus pumila) grown in two greenhouses with different air temperatures for 5 days. Compared with the non-girdled control in the low-temperature greenhouse (diurnal maximum air temperature <32 degrees C), low sink demand resulted in lower net photosynthetic rate (P(n)), stomatal conductance (g(s)) and transpiration rate (E) but higher leaf temperature on Day 5, while in the high-temperature greenhouse (diurnal maximum air temperature >36 degrees C), P(n), g(s) and E declined from Day 3 onwards. Moreover, gas exchange responded more to low sink demand in the high-temperature greenhouse than in the low-temperature greenhouse. Decreased P(n) at low sink demand was accompanied by lower intercellular CO(2) concentrations in the low-temperature greenhouse. However, decreased maximal photochemical efficiency, potential activity, efficiency of excitation capture, actual efficiency and photochemical quenching, with increased minimal fluorescence and non-photochemical quenching of photosystem II (PSII), were observed in low sink demand leaves only in the high-temperature greenhouse. In addition, low sink demand increased leaf starch and soluble carbohydrate content in both greenhouses but did not result in lower activity of enzymes involved in metabolism. Thus, decreased P(n) under low sink demand was independent of a direct effect of end-product feedback but rather depended on a high temperature threshold. The lower P(n) was likely due to stomatal limitation in the low-temperature greenhouse, but mainly due to non-stomatal limitation in the high-temperature greenhouse.
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Affiliation(s)
- Pei G Fan
- Institute of Botany, Chinese Academy of Sciences, 100093 Beijing, China
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Yamaki S. Metabolism and Accumulation of Sugars Translocated to Fruit and Their Regulation. ACTA ACUST UNITED AC 2010. [DOI: 10.2503/jjshs1.79.1] [Citation(s) in RCA: 75] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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Maier CA, Johnsen KH, Clinton BD, Ludovici KH. Relationships between stem CO(2) efflux, substrate supply, and growth in young loblolly pine trees. THE NEW PHYTOLOGIST 2010; 185:502-513. [PMID: 19878459 DOI: 10.1111/j.1469-8137.2009.03063.x] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
*We examined the relationships between stem CO(2) efflux (E(s)), diameter growth, and nonstructural carbohydrate concentration in loblolly pine trees. Carbohydrate supply was altered via stem girdling during rapid stem growth in the spring and after growth had ceased in the autumn. We hypothesized that substrate type and availability control the seasonal variation and temperature sensitivity of E(s). *The E(s) increased and decreased above and below the girdle, respectively, within 24 h of treatment. Seasonal variation in E(s) response to girdling corresponded to changes in stem soluble sugar and starch concentration. Relative to nongirdled trees, E(s) increased 94% above the girdle and decreased 50% below in the autumn compared with a 60% and 20% response at similar positions in the spring. *The sensitivity of E(s) to temperature decreased below the girdle in the autumn and spring and increased above the girdle but only in the autumn. Temperature-corrected E(s) was linearly related to soluble sugar (R(2) = 0.57) and starch (R(2) = 0.62) concentration. *We conclude that carbohydrate supply, primarily recently fixed photosynthate, strongly influences E(s) in Pinus taeda stems. Carbohydrate availability effects on E(s) obviate the utility of applying short-term temperature response functions across seasons.
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Affiliation(s)
- Chris A Maier
- USDA Forest Service, SRS, Research Triangle Park, NC, USA.
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