Phosphorus application and elevated CO2 enhance drought tolerance in field pea grown in a phosphorus-deficient vertisol

Long term co-application of biochar and fertilizer could increase soybean yield under continuous cropping: insights from photosynthetic physiology

BACKGROUND

Photosynthesis is the key to crop yield. The effect of biochar on photosynthetic physiology and soybean yield under continuous cropping is unclear. We conducted a long-term field experiment to investigate the effects of co-application of biochar and fertilizer (BCAF) on these parameters. Five treatments were established: F2 (fertilizer), B1F1 (3 t hm-2 biochar plus fertilizer), B1F2 (3 t hm-2 biochar plus reduced fertilizer), B2F1 (6 t hm-2 biochar plus fertilizer), and B2F2 (6 t hm-2 biochar plus reduced fertilizer).

RESULTS

BCAF increased chlorophyll and leaf area, enhancing soybean photosynthesis. The net photosynthetic rate (Pn ), transpiration rate (Tr ), stomatal conductance (Gs ), water use efficiency (WUE) and intercellular carbon dioxide (CO2 ) concentration (Ci ) were enhanced by BCAF. In addition, BCAF improved soybean photosystem II (PSII) photosynthetic performance, driving force, potential photochemical efficiency (Fv /F0 ), and quantum yield of electron transfer (φE0 ). Furthermore, BCAF enhanced the accumulation of photosynthetic products, such as soluble proteins, soluble sugars and sucrose content, resulting in higher leaf dry weight. Consequently, BCAF increased the soybean yield, with the highest increase of 41.54% in B2F1. The correlation analysis revealed positive relationships between soybean yield and chlorophyll, leaf area, maximal quantum yield of PSII (Fv /Fm ), electron transport flux per cross-section at t = 0 (ET0 /CS0 ), trapped energy flux per cross-section at t = 0 (TR0 /CS0 ), composite blade driving force (DFTotal ), and leaf dry weight.

CONCLUSIONS

We demonstrated that long-term BCAF enhances soybean photosynthesis under continuous planting, reduces fertilizer use and increases yield. This study reveals a novel way and theory to sustainably increase soybean productivity. © 2023 Society of Chemical Industry.

Phosphorus Plays Key Roles in Regulating Plants' Physiological Responses to Abiotic Stresses

Phosphorus (P), an essential macronutrient, plays a pivotal role in the growth and development of plants. However, the limited availability of phosphorus in soil presents significant challenges for crop productivity, especially when plants are subjected to abiotic stresses such as drought, salinity and extreme temperatures. Unraveling the intricate mechanisms through which phosphorus participates in the physiological responses of plants to abiotic stresses is essential to ensure the sustainability of agricultural production systems. This review aims to analyze the influence of phosphorus supply on various aspects of plant growth and plant development under hostile environmental conditions, with a special emphasis on stomatal development and operation. Furthermore, we discuss recently discovered genes associated with P-dependent stress regulation and evaluate the feasibility of implementing P-based agricultural practices to mitigate the adverse effects of abiotic stress. Our objective is to provide molecular and physiological insights into the role of P in regulating plants' tolerance to abiotic stresses, underscoring the significance of efficient P use strategies for agricultural sustainability. The potential benefits and limitations of P-based strategies and future research directions are also discussed.

Differential responses of contrasting low phosphorus tolerant cotton genotypes under low phosphorus and drought stress

BACKGROUND

Drought is one of the main reasons for low phosphorus (P) solubility and availability.

AIMS

The use of low P tolerant cotton genotypes might be a possible option to grow in drought conditions.

METHODS

This study investigates the tolerance to drought stress in contrasting low P-tolerant cotton genotypes (Jimian169; strong tolerant to low P and DES926; weak tolerant to low P). In hydroponic culture, the drought was artificially induced with 10% PEG in both cotton genotypes followed by low (0.01 mM KH₂PO₄) and normal (1 mM KH₂PO₄) P application.

RESULTS

The results showed that under low P, PEG-induced drought greatly inhibited growth, dry matter production, photosynthesis, P use efficiency, and led to oxidative stress from excessive malondialdehyde (MDA) and higher accumulation of reactive oxygen species (ROS), and these effects were more in DES926 than Jimian169. Moreover, Jimian169 alleviated oxidative damage by improving the antioxidant system, photosynthetic activities, and an increase in the levels of osmoprotectants like free amino acids, total soluble proteins, total soluble sugars, and proline.

CONCLUSIONS

The present study suggests that the low P-tolerant cotton genotype can tolerate drought conditions through high photosynthesis, antioxidant capacity, and osmotic adjustment.

Plant biomass responses to elevated CO2 are mediated by phosphorus uptake

Elevated atmospheric CO₂ concentrations [CO₂] potentially alter carbon (C) and phosphorus (P) cycles in terrestrial ecosystems. Although numerous field experiments and a few meta-analyses have been conducted, it is still largely unclear how the P cycle affects plant biomass responses under elevated [CO₂] globally. Here, we conducted a global synthesis by analyzing 111 studies on the responses of above- and belowground P cycling to elevated [CO₂], to examine how changes in the P cycle affect the plant biomass response to elevated [CO₂]. Our results show that elevated [CO₂] significantly increased plant aboveground biomass (+13 %), stem biomass (+4 %), leaf biomass (+11 %), belowground biomass (+12 %), and the root: shoot ratio (+7 %). Effects of elevated [CO₂] on aboveground biomass, belowground biomass, and root: shoot ratio were best explained by plant P uptake. In addition, elevated [CO₂]-induced changes in the aboveground P pool, leaf P pool, and leaf P concentration were modulated by ecological drivers, such as ΔCO₂, experimental duration, and aridity index. Our findings highlight the importance of plant P uptake for both above- and belowground plant biomass responses under elevated [CO₂], which should be considered in future biosphere models to improve predictions of terrestrial carbon-climate feedbacks.

Instigating prevalent abiotic stress resilience in crop by exogenous application of phytohormones and nutrient

In recent times, the demand for food and feed for the ever-increasing population has achieved unparalleled importance, which cannot afford crop yield loss. Now-a-days, the unpleasant situation of abiotic stress triggers crop improvement by affecting the different metabolic pathways of yield and quality advances worldwide. Abiotic stress like drought, salinity, cold, heat, flood, etc. in plants diverts the energy required for growth to prevent the plant from shock and maintain regular homeostasis. Hence, the plant yield is drastically reduced as the energy is utilized for overcoming the stress in plants. The application of phytohormones like the classical auxins, cytokinins, ethylene, and gibberellins, as well as more recent members including brassinosteroids, jasmonic acids, etc., along with both macro and micronutrients, have enhanced significant attention in creating key benefits such as reduction of ionic toxicity, improving oxidative stress, maintaining water-related balance, and gaseous exchange modification during abiotic stress conditions. Majority of phytohormones maintain homeostasis inside the cell by detoxifying the ROS and enhancing the antioxidant enzyme activities which can enhance tolerance in plants. At the molecular level, phytohormones activate stress signaling pathways or genes regulated by abscisic acid (ABA), salicylic acid (SA), Jasmonic acid (JA), and ethylene. The various stresses primarily cause nutrient deficiency and reduce the nutrient uptake of plants. The application of plant nutrients like N, K, Ca, and Mg are also involved in ROS scavenging activities through elevating antioxidants properties and finally decreasing cell membrane leakage and increasing the photosynthetic ability by resynthesizing the chlorophyll pigment. This present review highlighted the alteration of metabolic activities caused by abiotic stress in various crops, the changes of vital functions through the application of exogenous phytohormones and nutrition, as well as their interaction.

Elevated CO2 and Water Stress in Combination in Plants: Brothers in Arms or Partners in Crime?

The changing dynamics in the climate are the primary and important determinants of agriculture productivity. The effects of this changing climate on overall productivity in agriculture can be understood when we study the effects of individual components contributing to the changing climate on plants and crops. Elevated CO₂ (eCO₂) and drought due to high variability in rainfall is one of the important manifestations of the changing climate. There is a considerable amount of literature that addresses climate effects on plant systems from molecules to ecosystems. Of particular interest is the effect of increased CO₂ on plants in relation to drought and water stress. As it is known that one of the consistent effects of increased CO₂ in the atmosphere is increased photosynthesis, especially in C₃ plants, it will be interesting to know the effect of drought in relation to elevated CO₂. The potential of elevated CO₂ ameliorating the effects of water deficit stress is evident from literature, which suggests that these two agents are brothers in arms protecting the plant from stress rather than partners in crime, specifically for water deficit when in isolation. The possible mechanisms by which this occurs will be discussed in this minireview. Interpreting the effects of short-term and long-term exposure of plants to elevated CO₂ in the context of ameliorating the negative impacts of drought will show us the possible ways by which there can be effective adaption to crops in the changing climate scenario.

Plant Nutrition: An Effective Way to Alleviate Abiotic Stress in Agricultural Crops

By the year 2050, the world's population is predicted to have grown to around 9-10 billion people. The food demand in many countries continues to increase with population growth. Various abiotic stresses such as temperature, soil salinity and moisture all have an impact on plant growth and development at all levels of plant growth, including the overall plant, tissue cell, and even sub-cellular level. These abiotic stresses directly harm plants by causing protein denaturation and aggregation as well as increased fluidity of membrane lipids. In addition to direct effects, indirect damage also includes protein synthesis inhibition, protein breakdown, and membranous loss in chloroplasts and mitochondria. Abiotic stress during the reproductive stage results in flower drop, pollen sterility, pollen tube deformation, ovule abortion, and reduced yield. Plant nutrition is one of the most effective ways of reducing abiotic stress in agricultural crops. In this paper, we have discussed the effectiveness of different nutrients for alleviating abiotic stress. The roles of primary nutrients (nitrogen, phosphorous and potassium), secondary nutrients (calcium, magnesium and sulphur), micronutrients (zinc, boron, iron and copper), and beneficial nutrients (cobalt, selenium and silicon) in alleviating abiotic stress in crop plants are discussed.

Effects of Low Temperature Stress on Source-Sink Organs in Wheat and Phosphorus Mitigation Strategies

The 21st century presents many challenges to mankind, including climate change, fast growing human population, and serious concerns over food security. Wheat is a leading cereal crop that largely fulfills the global food needs. Low temperature stress accompanied by nutrient-starved soils is badly disrupting the source-sink relationship of wheat, thus causing an acute decline in final yield and deteriorating the grain quality. This review paper aimed to understand how low temperature stress affects wheat source-sink organs (i.e., leaves, roots, and spikes) and how phosphorus application reliefs in alleviating its harmful consequences. Also, we discussed mitigation strategies to enhance wheat capacity to adapt to varying temperature extremes and made rational recommendations based on modern agronomic and breeding approaches. Therefore, this study is likely to establish a solid foundation for improving the tolerance to low temperature stress and to improve its phosphorus utilization efficiency in wheat.

Synergistic effect of P and K interaction on yield and yield components of mungbean (Vigna radiata (L.) Wilczek) varieties

Background

The relation between the macronutrients P and K seems to be synergistic due to the beneficial effects of the interaction between (P × K) and varies according to the variety used. Therefore, two field experiments were conducted during 2018 and 2019 summer seasons to study the effect of interaction of phosphatic fertilization at 0, 37.5 and 75 kg P2O5 ha−1 and potassic fertilization at 0 and 57.6 kg K2O ha−1 on the yield and yield components of two mungbean varieties, viz. Kawmy-l and V2010, as well as determining the relationship between the two nutrients interaction.

Results

The results showed that there were varietal differences in yield and yield components regardless fertilizer application. Either phosphatic or potassic fertilization significantly increased mungbean yield and yield components traits. Significant effects due to the interaction (V × P) were reported on yield component traits in both seasons. Furthermore, the triple interaction (V × P × K) indicates that synergistic effect was reported for the two varieties and was more clearer for V2010 where it needed both of P and K nutrients to out yield the greatest seed yield ha−1, while Kawmy-1 gave the greatest seed yield ha−1 without K application.

Conclusion

It could be concluded from this study that mungbean varieties differ in their response to the synergistic interaction effect of P and K and the combination of 75 kg P2O5 + 57.6 kg K2O is preferable for V2010 and 75 kg P2O5 alone for Kawmy-1 to produce the greatest yield.

Identification of soybean phosphorous efficiency QTLs and genes using chlorophyll fluorescence parameters through GWAS and RNA-seq

MAIN CONCLUSION

Soybean phosphorous efficiency QTLs were identified and candidate genes were predicted using chlorophyll fluorescence parameters through GWAS and RNA-seq. Phosphorus (P) is an essential nutrient element for crop growth and development, lack of P uptake seriously affects yield in various crops. Photosynthesis is the basis of crop production, while it is very sensitive to P deficiency. It is of great importance to study the genetic relationship between photosynthesis and P efficiency to provide genetic insight for soybean improvement. In this study, a genome-wide association study (GWAS) was performed using 292,035 SNPs and the ratios of four main chlorophyll fluorescence parameters of 219 diverse soybean accessions under P deficiency and normal P across three experiments. In total, 52 SNPs in 12 genomic regions were detected in association with the four main chlorophyll fluorescence parameters under sufficient or deficient P levels. Combined it with RNA-seq analysis, we predicted three candidate genes for the significant genomic regions. For example, the expression level of the candidate gene (Glyma.18g092900) in P deficiency tolerant accession was three times higher than that of P deficiency sensitive one under phosphorous deficiency condition. This study provides insight into genetic links between photosynthetic and phosphorous efficiency and further functional analysis will provide valuable information for understanding the underlying genetic mechanism to facilitate marker-assisted breeding in soybean.

Molecular Evaluation of Kyoho Grape Leaf and Berry Characteristics Influenced by Different NPK Fertilizers

Fertilization, a fundamental aspect of a plant’s life, has been of great concern for agricultural specialists to minimize the yield gap between actual and potential yield. Around the globe, fertilizers with different NPK ratios are being used to attain a better yield of grape. To find the suitable commercially available fertilizer for quality grape production, a 2 years (2017–2018) study was conducted for the evaluation of 10 fertilizers with different NPK ratios. Commercial fertilizers included were Zhanlan (16:16:16), Garsoni (15:15:15), Acron (16:16:16), Norway (21:7:12), Peters 1 (30:10:10), Nutrivant (14:14:30), Peters 2 (20:20:20), UMAX (15:15:15), G2 (20:20:20), and Yara (15:15:15). The fertilizer application rate was 20 g plant⁻¹, and each was applied at L-29, L-33, and L-36 phenological stages. Chlorophylls, carotenoids, macro/micronutrients in leaf, and anthocyanin derivatives in grape peel were evaluated. Expression levels of 24 genes, including nitrogen, phosphorous, potassium, and anthocyanin pathways in leaf, peel, and pulp were validated by qPCR at L-29, L-33, and L-36 stages. Results indicated that Norway (21:7:12) and Peters 1 (30:10:10) increased carotenoids, chlorophylls, and anthocyanins in leaves, while Zhanlan (16:16:16) improved fruit biochemical attributes, and anthocyanin (cyanidin, delphinidin, petunidin, malvidin, peonidin, and pelargonidin contents). However, a better grape yield was obtained by the application of Peters 1 (30:10:10). Potassium pathway genes were upregulated by Nutrivant (14:14:30), phosphorous pathway genes by Peters 2 (20:20:20), and nitrogen pathway genes by Peters 1 (30:10:10), while Nutrivant (14:14:30) upregulated anthocyanin pathway genes and simultaneously enhanced anthocyanin biosynthesis in berry peels. Results of two years’ study concluded that Peters 1 (30:10:10) was proved better to increase yield, while Zhanlan (14:14:30) was superior in improving anthocyanin biosynthesis.

Physiological and Biochemical Characterization of the GABA Shunt Pathway in Pea (Pisum sativum L.) Seedlings under Drought Stress

The physiological and biochemical role of the γ-aminobutyric acid (GABA) shunt pathway in green pea seedlings (Pisum sativum L.) was studied in response to soil water holding capacity levels: 80%, 60%, 40%, 20%, and 10% grown under continuous light at 25 °C for 7 days and 14 days, separately. Characterization of seeds germination pattern, seedlings growth (plant height, fresh and dry weight, and chlorophyll contents), GABA shunt metabolite (GABA, glutamate, and alanine) levels, total protein and carbohydrate levels, and oxidative damage (MDA level) were examined. Data showed a significant effect of drought stress on seed germination, plant growth, GABA shunt metabolites level, total protein and carbohydrate contents, and MDA level. A significant decline in seed germination percentage was recorded at a 20% drought level, which indicated that 20% of soil water holding capacity is the threshold value of water availability for normal germination after 14 days. Seedling fresh weight, dry weight, and plant height were significantly reduced with a positive correlation as water availability was decreased. There was a significant decrease with a positive correlation in Chl a and Chl b contents in response to 7 days and 14 days of drought. GABA shunt metabolites were significantly increased with a negative correlation as water availability decreased. Pea seedlings showed a significant increase in protein content as drought stress was increased. Total carbohydrate levels increased significantly when the amount of water availability decreased. MDA content increased slightly but significantly after 7 days and sharply after 14 days under all water stress levels. The maximum increase in MDA content was observed at 20% and 10% water levels. Overall, the significant increases in GABA, protein and carbohydrate contents were to cope with the physiological impact of drought stress on Pisum sativum L. seedlings by maintaining cellular osmotic adjustment, protecting plants from oxidative stress, balancing carbon and nitrogen (C:N) metabolism, and maintaining cell metabolic homeostasis and cell turgor. The results presented in this study indicated that severe (less than 40% water content of the holding capacity) and long-term drought stress should be avoided during the germination stage to ensure proper seedling growth and metabolism in Pisum sativum L.

Root architecture for improved resource capture: trade-offs in complex environments

Root architecture is a promising breeding target for developing resource-efficient crops. Breeders and plant physiologists have called for root ideotypes that have narrow, deep root systems for improved water and nitrate capture, or wide, shallower root systems for better uptake of less mobile topsoil nutrients such as phosphorus. Yet evidence of relationships between root architecture and crop yield is limited. Many studies focus on the response to a single constraint, despite the fact that crops are frequently exposed to multiple soil constraints. For example, in dryland soils under no-till management, topsoil nutrient stratification is an emergent profile characteristic, leading to spatial separation of water and nutrients as the soil profile dries. This results in spatio-temporal trade-offs between efficient resource capture and pre-defined root ideotypes developed to counter a single constraint. We believe there is need to identify and better understand trade-offs involved in the efficient capture of multiple, spatially disjunct soil resources. Additionally, how these trade-offs interact with genotype (root architecture), environment (soil constraints), and management (agronomy) are critical unknowns. We argue that identifying root traits that enable efficient capture of multiple soil resources under fluctuating environmental constraints is a key step towards meeting the challenges of global food security.

Extending thermotolerance to tomato seedlings by inoculation with SA1 isolate of Bacillus cereus and comparison with exogenous humic acid application

Heat stress is one of the major abiotic stresses that impair plant growth and crop productivity. Plant growth-promoting endophytic bacteria (PGPEB) and humic acid (HA) are used as bio-stimulants and ecofriendly approaches to improve agriculture crop production and counteract the negative effects of heat stress. Current study aimed to analyze the effect of thermotolerant SA1 an isolate of Bacillus cereus and HA on tomato seedlings. The results showed that combine application of SA1+HA significantly improved the biomass and chlorophyll fluorescence of tomato plants under normal and heat stress conditions. Heat stress increased abscisic acid (ABA) and reduced salicylic acid (SA) content; however, combined application of SA1+HA markedly reduced ABA and increased SA. Antioxidant enzymes activities revealed that SA1 and HA treated plants exhibited increased levels of ascorbate peroxidase (APX), superoxide dismutase (SOD), and reduced glutathione (GSH). In addition, heat stress markedly reduced the amino acid contents; however, the amino acids were increased with co-application of SA1+HA. Similarly, inductively-coupled plasma mass-spectrometry results showed that plants treated with SA1+HA exhibited significantly higher iron (Fe+), phosphorus (P), and potassium (K+) uptake during heat stress. Heat stress increased the relative expression of SlWRKY33b and autophagy-related (SlATG5) genes, whereas co-application of SA1+HA augmented the heat stress response and reduced SlWRKY33b and SlATG5 expression. The heat stress-responsive transcription factor (SlHsfA1a) and high-affinity potassium transporter (SlHKT1) were upregulated in SA1+HA-treated plants. In conclusion, current findings suggest that co-application with SA1+HA can be used for the mitigation of heat stress damage in tomato plants and can be commercialized as a biofertilizer.

Effects of multiple N, P, and K fertilizer combinations on adzuki bean (Vigna angularis) yield in a semi-arid region of northeastern China

Nitrogen (N), phosphorus (P), and potassium (K) exert various effects on adzuki bean yields. Our research was conducted in a semi-arid area, and four test sites were established in environments that have chernozem or sandy loam soils. During a five-year period, the effects of N, P, and K fertilizers on yield were comprehensively investigated in field trials (2014–2016) and for model-implementation trials (2017–2018), with models established prior to the latter. In the field trials, 23 treatments comprising different N, P, and K combinations significantly affected both yield and yield components, and regression analysis indicated that the experimental results were suitable for model establishment. The model subsequently demonstrated that the yield and the yield components were more sensitive to N and K fertilizer than to P fertilizer. Moreover, the yield and yield components increased. These yield increases were intense in response to the 0.5 to 1.34 levels in terms of the single effects; interaction effects; and the effects of combinations of N, P, and K fertilizers. Moreover, the effects of combinations of N, P, and K fertilizers were more significant on yield than were the single or interaction effects of N, P, and K fertilizers. The optimal fertilizer combination that resulted in high yields (≥1941.53 kg ha⁻¹) comprised 57.23–68.43 kg ha⁻¹ N, 36.04–47.32 kg ha⁻¹ P₂O₅ and 50.29–61.27 kg ha⁻¹ K₂O. The fertilizer combination that resulted in the maximum yield was 62.98 kg ha⁻¹ N, 47.04 kg ha⁻¹ P₂O₅ and 59.95 kg ha⁻¹ K₂O (N:P₂O₅:K₂O = 1:0.75:0.95), which produced the model-expected yield in trials at multiple sites. An economical fertilizer combination was determined on the basis of the best fertilizer measures in consideration of the cost of fertilizer and seed; this combination achieved yields of 2236.17 kg ha⁻¹, the profit was 15,653.16 Yuan ha⁻¹, and the corresponding rates were 57.60 kg ha⁻¹ N, 47.03 kg ha⁻¹ P₂O₅, and 31.64 kg ha⁻¹ K₂O (N:P₂O₅:K₂O = 1:0.82:0.55).

Impact of elevated CO2 on C:N:P ratio among soybean cultivars

Elevated atmospheric CO2 concentration (eCO2) exerts significant influence on nutrient requirement in plant. The investigation of C:N:P ratios in major cropping soils is important for managing nutrient balance and maximizing their use efficiency in future farming systems. This study aimed to examine the effect of eCO2 on the C:N:P ratios in different plant parts among soybean cultivars. Twenty-four soybean cultivars were planted in open top chambers at two CO2 concentrations (390 and 550 ppm) and sampled at the initial pod filling stage (R5) and the full maturity stage (R8). The C, N and P concentrations in root, stem, leaf and seed were determined. Elevated CO2 decreased the N concentrations in stem (-5.1%) and leaf (-3.2%) at R5, and in root (-24%), stem (-25%) and seed (-6.2%) at R8, resulting in a significant decrease of C:N ratio in the corresponding parts. The P concentration was significantly increased in root (6.0%), stem (7.9%) and leaf (16%) at R5, and in root (2.6%), stem (29%) and seed (16%) at R8 across 24 cultivars, leading to a decrease in the C:P ratio. Elevated CO2 significantly decreased the N:P ratio in root (-4.5%), stem (-12%) and leaf (-17%) at R5, and in root (-26%), stem (-57%) and seed (-22%) at R8. Furthermore, the response of C:N:P ratios to eCO2 varied greatly among soybean cultivars leading to significant CO2 × cultivar interactions. Nitrogen, but not P was the limiting factor for the soybean plants grown in Mollisols under eCO2. The considerable variation in the C:N:P ratios among cultivars in response to eCO2 indicates a potential improvement in soybean adaptability to climate change via selection new cultivars. Cultivars SN22 and ZH4 that did not considerably altered the C:N and C:P ratios in response to eCO2 are likely the optimal genomes in soybean breeding programs for eCO2 adaption.

The bHLH family member ZmPTF1 regulates drought tolerance in maize by promoting root development and abscisic acid synthesis

Drought stress is the most important environmental stress limiting maize production. ZmPTF1, a phosphate starvation-induced basic helix-loop-helix (bHLH) transcription factor, contributes to root development and low-phosphate tolerance in maize. Here, ZmPTF1 expression, drought tolerance, and the underlying mechanisms were studied by using maize ZmPTF1 overexpression lines and mutants. ZmPTF1 was found to be a positive regulator of root development, ABA synthesis, signalling pathways, and drought tolerance. ZmPTF1 was also found to bind to the G-box element within the promoter of 9-cis-epoxycarotenoid dioxygenase (NCED), C-repeat-binding factor (CBF4), ATAF2/NAC081, NAC30, and other transcription factors, and to act as a positive regulator of the expression of those genes. The dramatically upregulated NCEDs led to increased abscisic acid (ABA) synthesis and activation of the ABA signalling pathway. The up-regulated transcription factors hierarchically regulate the expression of genes involved in root development, stress responses, and modifications of transcriptional regulation. The improved root system, increased ABA content, and activated ABA-, CBF4-, ATAF2-, and NAC30-mediated stress responses increased the drought tolerance of the ZmPTF1 overexpression lines, while the mutants showed opposite trends. This study describes a useful gene for transgenic breeding and helps us understand the role of a bHLH protein in plant root development and stress responses.

Different ways to die in a changing world: Consequences of climate change for tree species performance and survival through an ecophysiological perspective

Anthropogenic activities such as uncontrolled deforestation and increasing greenhouse gas emissions are responsible for triggering a series of environmental imbalances that affect the Earth's complex climate dynamics. As a consequence of these changes, several climate models forecast an intensification of extreme weather events over the upcoming decades, including heat waves and increasingly severe drought and flood episodes. The occurrence of such extreme weather will prompt profound changes in several plant communities, resulting in massive forest dieback events that can trigger a massive loss of biodiversity in several biomes worldwide. Despite the gravity of the situation, our knowledge regarding how extreme weather events can undermine the performance, survival, and distribution of forest species remains very fragmented. Therefore, the present review aimed to provide a broad and integrated perspective of the main biochemical, physiological, and morpho-anatomical disorders that may compromise the performance and survival of forest species exposed to climate change factors, particularly drought, flooding, and global warming. In addition, we also discuss the controversial effects of high CO2 concentrations in enhancing plant growth and reducing the deleterious effects of some extreme climatic events. We conclude with a discussion about the possible effects that the factors associated with the climate change might have on species distribution and forest composition.

Effects of elevated CO2 on plant C-N-P stoichiometry in terrestrial ecosystems: A meta-analysis

A substantial number of experiments have so far been carried out to study the response of the C-N-P stoichiometry of terrestrial plants to the rising CO₂ level of the earth. However, there is a need of systematic evaluation for assessing the impact of the elevated CO₂ on plant C-N-P stoichiometry. In the present investigation, a comprehensive meta-analysis involving 386 published reports and including 4481 observations has been carried out. The goal of the research was to determine the response of plants to their C-N-P stoichiometry due to elevated levels of global atmospheric CO₂. The results showed that rising CO₂ altered the concentration of C (+2.19%, P < 0.05), N (-9.73%, P < 0.001) and P (-3.23%, P < 0.001) and C:N (+13.29%, P < 0.001) and N:P ratios (-7.32%, P < 0.0001). Overall, a slightly increasing trend in the C:P ratio (P > 0.05) in the plant was observed. However, plant leaf, shoot and herbaceous type of plants showed more sensitivity to rising CO₂. CO₂ magnitude exhibited a positive effect (P < 0.05) on C:N ratio. Additionally, "CO₂ acclimation" hypothesis as proposed by the authors of the current paper was also tested in the study. Results obtained, especially, show changes of C and N concentrations and C:P ratio to an obvious down-regulation for long-term CO₂ fumigation. At spatial scales, a reduction of plant N concentration was found to be higher in the southern hemisphere. The CO₂ enrichment methods affected the plant C-N-P stoichiometry. Compared to FACE (free-air CO₂ enrichment), OTC (open top chamber) showed larger changes of C, N, P, and N:P. The results of the present study should, therefore, become helpful to offer a better understanding towards the response of the terrestrial plant C-N-P stoichiometry to an elevated global atmospheric CO₂ in the future.

Quantifying Phosphorus and Water Demand to Attain Maximum Growth of Solanum tuberosum in a CO2-Enriched Environment

Growth promotion by ambient CO₂ enrichment may be advantageous for crop growth but this may be influenced by soil nutrient availability. Therefore, we quantified potato (Solanum tuberosum L.) growth responses to phosphorus (P) supply under ambient (a[CO₂]) and elevated (doubled) CO₂ concentration (e[CO₂]). A pot experiment was conducted in controlled-environment chambers with a[CO₂] and e[CO₂] combined with six P supply rates. We obtained response curves of biomass against P supply rates under a[CO₂] and e[CO₂] (R² = 0.996 and R² = 0.992, respectively). A strong interaction between [CO₂] and P was found. Overall, e[CO₂] enhanced maximum biomass accumulation (1.5-fold) and water-use efficiency (WUE) (1.5-fold), but not total water use. To reach these maxima, minimum P supply rate at both [CO₂] conditions was similar. Foliar critical P concentration (i.e., minimum [P] to reach 90% of maximum growth) was also similar at nearly 110 mg P m^-2. Doubling [CO₂] did not increase P and water demand of potato plants, thus enabling the promotion of maximum growth without additional P or water supply, but via a significant increase in WUE (9.6 g biomass kg^-1 water transpired), presumably owing to the interaction between CO₂ and P.

Nitrogen, phosphorus, and potassium fertilization to achieve expected yield and improve yield components of mung bean

Mung bean (Vigna radiata L.) is an important edible bean in the human diet worldwide. However, its growth, development, and yield may be restricted or limited by insufficient or unbalanced nitrogen (N), phosphorus (P), and potassium (K) fertilization. Despite this, there are few long-term studies of the effects of varying levels of N, P, and K combined fertilizers and the optimal fertilization for improving mung bean yield and quality. This study was conducted to optimize the fertilization strategies for high yield and to improve yield components (pods per plant, seeds per pod, and 100-seed weight) in the Bailv9 mung bean cultivar, 23 treatments were tested in 2013-2015, using a three-factor (N, P, and K fertilizers), five-level quadratic orthogonal rotation combination design. Our studies showed that, the N, P, and K fertilizers significantly influenced the pods per plant and yield, which increased and then decreased with the increasing N, P, and K fertilizers. The 100-seed weight was significantly affected by the N and P fertilization, and it was increased consistently with the increasing N fertilizer, and decreased significantly with the increasing P fertilizer. Whereas, the seeds per pod significantly decreased with the increasing N and K fertilizers, and the P fertilizer had no significant effect on it. The NP interaction had a significant effect on yield and pods per plant at high N levels, while the NK interaction had a significant but opposite effect on yield at low N levels. The optimal fertilization conditions to obtain yield >2,141.69 kg ha-1 were 34.38-42.62 kg ha-1 N, 17.55-21.70 kg ha-1 P2O5, and 53.23-67.29 kg ha-1 K2O. Moreover, the optimal N, P, and K fertilization interval to achieve pods per plant > 23.41 and the optimal N fertilization to achieve a 100-seed weight > 6.58 g intersected with the interval for yield, but the seeds per pod did not. The fertilizer ratio for the maximum yield was N:P2O5:K2O = 1:0.5:1.59. Following three years experimentation, the optimal fertilization measures were validated in 2016-2017, the results indicated that yield increased by 19.6% than that obtained using conventional fertilization. The results of this study provide a theoretical basis and technical guidance for high-yield mung bean cultivation using the optimal fertilization measures.

Phosphorous Application Improves Drought Tolerance of Phoebe zhennan

Phoebe zhennan (Gold Phoebe) is a threatened tree species in China and a valuable and important source of wood and bioactive compounds used in medicine. Apart from anthropogenic disturbances, several biotic constraints currently restrict its growth and development. However, little attention has been given to building adaptive strategies for its conservation by examining its morphological and physio-biochemical responses to drought stress, and the role of fertilizers on these responses. A randomized experimental design was used to investigate the effects of two levels of irrigation (well-watered and drought-stressed) and phosphorous (P) fertilization treatment (with and without P) to assess the morphological and physio-biochemical responses of P. zhennan seedlings to drought stress. In addition, we evaluated whether P application could mitigate the negative impacts of drought on plant growth and metabolism. Drought stress had a significant negative effect on the growth and metabolic processes of P. zhennan. Despite this, reduced leaf area, limited stomatal conductance, reduced transpiration rate, increased water use efficiency, enhanced antioxidant enzymes activities, and osmolytes accumulation suggested that the species has good adaptive strategies for tolerating drought stress. Application of P had a significant positive effect on root biomass, signifying its improved water extracting capacity from the soil. Moreover, P fertilization significantly increased leaf relative water content, net photosynthetic rate, and maximal quantum efficiency of PSII under drought stress conditions. This may be attributable to several factors, such as enhanced root biomass, decreased malondialdehyde content, and the up-regulation of chloroplast pigments, osmolytes, and nitrogenous compounds. However, P application had only a slight or negligible effect on the growth and metabolism of well-watered plants. In conclusion, P. zhennan has a strong capability for drought resistance, while P application facilitates and improves drought tolerance mostly through physio-biochemical adjustments, regardless of water availability. It is imperative to explore the underlying metabolic mechanisms and effects of different levels of P fertilization on P. zhennan under drought conditions in order to design appropriate conservation and management strategies for this species, which is at risk of extinction.

Elevated-CO2 Response of Stomata and Its Dependence on Environmental Factors

Stomata control the flow of gases between plants and the atmosphere. This review is centered on stomatal responses to elevated CO2 concentration and considers other key environmental factors and underlying mechanisms at multiple levels. First, an outline of general responses in stomatal conductance under elevated CO2 is presented. Second, stomatal density response, its development, and the trade-off with leaf growth under elevated CO2 conditions are depicted. Third, the molecular mechanism regulating guard cell movement at elevated CO2 is suggested. Finally, the interactive effects of elevated CO2 with other factors critical to stomatal behavior are reviewed. It may be useful to better understand how stomata respond to elevated CO2 levels while considering other key environmental factors and mechanisms, including molecular mechanism, biochemical processes, and ecophysiological regulation. This understanding may provide profound new insights into how plants cope with climate change.

Elevated-CO2 Response of Stomata and Its Dependence on Environmental Factors

Stomata control the flow of gases between plants and the atmosphere. This review is centered on stomatal responses to elevated CO2 concentration and considers other key environmental factors and underlying mechanisms at multiple levels. First, an outline of general responses in stomatal conductance under elevated CO2 is presented. Second, stomatal density response, its development, and the trade-off with leaf growth under elevated CO2 conditions are depicted. Third, the molecular mechanism regulating guard cell movement at elevated CO2 is suggested. Finally, the interactive effects of elevated CO2 with other factors critical to stomatal behavior are reviewed. It may be useful to better understand how stomata respond to elevated CO2 levels while considering other key environmental factors and mechanisms, including molecular mechanism, biochemical processes, and ecophysiological regulation. This understanding may provide profound new insights into how plants cope with climate change.

Plants and climate change: complexities and surprises

BACKGROUND

Anthropogenic climate change (ACC) will influence all aspects of plant biology over coming decades. Many changes in wild species have already been well-documented as a result of increased atmospheric CO2 concentrations, warming climate and changing precipitation regimes. A wealth of available data has allowed the use of meta-analyses to examine plant-climate interactions on more sophisticated levels than before. These analyses have revealed major differences in plant response among groups, e.g. with respect to functional traits, taxonomy, life-history and provenance. Interestingly, these meta-analyses have also exposed unexpected mismatches between theory, experimental, and observational studies.

SCOPE

We reviewed the literature on species' responses to ACC, finding ∼42 % of 4000 species studied globally are plants (primarily terrestrial). We review impacts on phenology, distributions, ecophysiology, regeneration biology, plant-plant and plant-herbivore interactions, and the roles of plasticity and evolution. We focused on apparent deviations from expectation, and highlighted cases where more sophisticated analyses revealed that unexpected changes were, in fact, responses to ACC.

CONCLUSIONS

We found that conventionally expected responses are generally well-understood, and that it is the aberrant responses that are now yielding greater insight into current and possible future impacts of ACC. We argue that inconclusive, unexpected, or counter-intuitive results should be embraced in order to understand apparent disconnects between theory, prediction, and observation. We highlight prime examples from the collection of papers in this Special Issue, as well as general literature. We found use of plant functional groupings/traits had mixed success, but that some underutilized approaches, such as Grime's C/S/R strategies, when incorporated, have improved understanding of observed responses. Despite inherent difficulties, we highlight the need for ecologists to conduct community-level experiments in systems that replicate multiple aspects of ACC. Specifically, we call for development of coordinating experiments across networks of field sites, both natural and man-made.

The impact of elevated carbon dioxide on the phosphorus nutrition of plants: a review

BACKGROUND

Increasing attention is being focused on the influence of rapid increases in atmospheric CO2 concentration on nutrient cycling in ecosystems. An understanding of how elevated CO2 affects plant utilization and acquisition of phosphorus (P) will be critical for P management to maintain ecosystem sustainability in P-deficient regions.

SCOPE

This review focuses on the impact of elevated CO2 on plant P demand, utilization in plants and P acquisition from soil. Several knowledge gaps on elevated CO2-P associations are highlighted.

CONCLUSIONS

Significant increases in P demand by plants are likely to happen under elevated CO2 due to the stimulation of photosynthesis, and subsequent growth responses. Elevated CO2 alters P acquisition through changes in root morphology and increases in rooting depth. Moreover, the quantity and composition of root exudates are likely to change under elevated CO2, due to the changes in carbon fluxes along the glycolytic pathway and the tricarboxylic acid cycle. As a consequence, these root exudates may lead to P mobilization by the chelation of P from sparingly soluble P complexes, by the alteration of the biochemical environment and by changes to microbial activity in the rhizosphere. Future research on chemical, molecular, microbiological and physiological aspects is needed to improve understanding of how elevated CO2 might affect the use and acquisition of P by plants.