Improving potato drought tolerance through the induction of long-term water stress memory

Knowledge of drought tolerance in potato is limited and very little is known about stress memory in this crop. In the present study, long-term stress memory was tested on tuber yield and drought tolerance related traits in three potato varieties (Unica, Désirée and Sarnav) with contrasted yields under water restriction. Seed tubers produced by plants grown under non-restricted (non-primed tubers) and restricted (primed tubers) water conditions were sown and exposed to similar watering treatments. Tuber yield and leaf greenness of plants from primed and non-primed seeds as well as tuber carbon isotope discrimination (Δ(13)C) and antioxidant activity (AA) responses to watering treatments were compared. Higher tuber yield, both under non-restricted and restricted water regimes, was produced by primed Sarnav plants. The decrease of tuber yield and Δ(13)C with water restriction was lower in primed Unica plants. Long-term stress memory consequently appears to be highly genotype-dependent in potato. Its expression in plants originated from primed tubers and facing water restriction seems to be positively associated to the degree of inherent capability of the cultivar to yield under water restriction. However, other effects of priming appear to be genotype-independent as priming enhanced the tuber AA in response to water restriction in the three varieties.

Aluminum uptake, translocation, physiological changes, and overall growth inhibition in rice genotypes (Oryza sativa) at vegetative stage

Aluminum (Al) contamination in acidic soil is a major problem in paddy field, causing grain yield loss, especially in central plains of Thailand. The objective of this study was to assess Al content in the root tissues, its translocation to the leaves, and Al toxicity in three genotypes of rice, RD35 (local acidic-tolerant), Azucena (positive-check Al-tolerant), and IR64 (high yielding) under 0 (control) or 1 mM AlCl₃ (Al toxicity) at pH 4.5. Al content in the root tissues of rice cv. RD35 under 1 mM AlCl₃ was peaked at 4.18 mg g^‒1 DW and significantly translocated to leaf tissues (0.35 mg g^‒1 DW), leading to reduced leaf greenness (SPAD) (by 44.9% over the control) and declined net photosynthetic rate (P_n) (by 54.5% over the control). In contrast, Al level in cvs. Azucena and IR64 was restricted in the roots (2.12 mg g^‒1 DW) with low amount of translocation in the leaf tissues (0.26 mg g^‒1 DW), resulting in maintained values of SPAD and P_n. In cv. RD35, root and shoot traits including root length, root fresh weight, shoot height, shoot fresh weight, and shoot dry weight in 1 mM Al treatment were significantly dropped by > 35% over the control, whereas these parameters in cvs. Azucena and IR64 were retained. Based on the results, RD35 rice genotype was identified as Al sensitive as it demonstrated Al toxicity in both aboveground and belowground parts, whereas Azucena and IR64 were found tolerant to 1 mM Al as they demonstrated storage of Al in the root tissues to reduce toxicity in the leaf tissues. The study suggests that root traits, shoot attributes, chlorophyll degradation, and photosynthetic reduction can be successfully employed for the screening of Al-tolerant genotypes in rice breeding programs.

Outburst of senescence-related VOC emissions from a bioenergy poplar plantation

Leaf senescence is a catabolic process that emits volatile organic compounds (VOCs). In densely planted monocultures these VOC emissions occur in outbursts that might be relevant for the local air quality since these VOCs are typically oxygenated. The VOC emissions of a high-density poplar (Populus) bioenergy plantation were monitored along with meteorological parameters, CO₂ and H₂O exchanges, canopy greenness, and leaf area index during the second half of the year 2015. The emissions of 25 VOCs peaked at the beginning of September, coinciding with the onset of senescence. Together these VOC emissions amounted to a total of 2.85 mmol m^-2, translated into 98.3 mg C m^-2. The emission peak was mainly composed of oxygenated VOCs as methanol, acetic acid, and lipoxygenase products that are all typical for catabolic processes. So, the senescence process of the poplar plantation was very well reflected in the peak of VOC emissions.

Recommended nitrogen rates and the verification of effects based on leaf SPAD readings of rice

Modern rice production systems need a reliable, easy-to-use, efficient, and environmentally-friendly method to determine plant nitrogen (N) status , predict grain yield, and optimize N management. We conducted field experiments to determine the influence of different N rates on Soil Plant Analysis Development (SPAD) readings of rice leaves. We also performed field validations to evaluate the grain yield and N use efficiency under recommended N rates. Our results showed that leaf SPAD readings increased as N rates increased. We applied the recommended N based on the relationships between the N rates and leaf SPAD readings at the tillering and booting stages. The recommended N decreased N rates and improved N use efficiency without sacrificing grain yield. When compared to farmer practices (FP), the recommended N rates of optimization (OPT) decreased by 5.8% and 10.0%, respectively. In comparison with FP, the N agronomic efficiency of OPT increased by 5.8 and 10.0% while the partial factor productivity of N increased by 6.0 and 14.2%, respectively. The SPAD meter may be a reliable tool to analyze the N in rice, estimate real-time N fertilization, and improve N use efficiency.

Expression levels of nitrogen assimilation-related genes, physiological responses, and morphological adaptations of three indica rice (Oryza sativa L. ssp. indica) genotypes subjected to nitrogen starvation conditions

Nitrogen (N) is an essential nutrient available to the plants in form of nitrate and ammonium. It is a macronutrient important for the plant growth and development, especially in cereal crops, which consume it for the production of amino acids, proteins/enzymes, nucleic acids, cell wall complexes, plant hormones, and vitamins. In rice production, 17 kg N uptake is required to produce 1 ton of rice. Considering this, many techniques have been developed to evaluate leaf greenness or SPAD value for assessing the amount of N application in the rice cultivar to maximize the grain yield. The aim of the present study was to investigate the morpho-physiological characteristics and relative expression level of N assimilation in three different rice genotypes (MT2, RD31, KDML105) under 1.00 × (full N), 0.50 × , 0.25 × (N depletion), and 0.00 × (N deficiency) at seedling stage and the morpho-physiological traits and the grain yield attributes under 1.00 × (full N) and 0.25 × (N depletion) were compared. Leaf chlorosis and growth inhibition in rice seedlings under N deficiency were evidently observed. Shoot height, number of leaves, shoot fresh weight, shoot dry weight, and root fresh weight in KDML105 under N deficiency were decreased by 27.65%, 42.11%, 65.44%, 47.90%, and 54.09% over the control (full N). Likewise, leaf greenness was lowest in KDML105 under N deficiency (78.57% reduction over the full N), leading to low photosynthetic abilities. In addition, expression of nitrogen assimilation-related genes, OsNR1, OsGln1;1, and OsGln2, in KDML105 under N depletion were increased within 3 h and then declined after the long incubation period, whereas those were unchanged in cvs. MT2 and RD31. Similarly, relative expression level of OsNADH-GOGAT, OsFd-GOGAT, and OsAspAt1 in KDML105 was peaked when subjected to 0.50 × N for 6 h and then declined after the long incubation period. Moreover, overall growth characters and physiological changes in cv. RD31 at vegetative stage under 0.25 × N were retained better than those in cvs. KDML105 and MT2, resulting in high yield at the harvesting process. In summary, N assimilated-related genes in rice seedlings under N depletion were rapidly regulated within 3-6 h, especially cv. KDML105 and MT2, then downregulated, resulting in physiological changes, growth inhibition, and yield reduction.

Optimum concentrations of potassium and zinc for better performance, nutritional, and biochemical quality of hydroponically cultivated Spinacia oleracea Cv. Virofly

In order to evaluate micro and macronutrient balance in vegetable growth, a study on greenness, yield, nutritional value, as well as biochemical status in spinach, has been conducted in a greenhouse, utilising the different concentrations of zinc (Zn) and potassium (K) in the nutrient solution. So, three concentrations of Zn (0.22, 5, and 10 mg L- 1) and K (39, 78, and 117 mg L- 1) were applied to hydroponically grown spinach (Spinacia oleracea cv. Virofly) through a factorial experiment based on a randomized complete design with three replications. The results showed that along with increasing concentrations of Zn and K in a nutrient solution, chlorophyll index and plant performance were increased although Zn showed more influence than K. The maximum plant yield was observed at 117 mg L- 1 of K in combination with both concentrations of Zn (5 and 10 mg L- 1). Along with an increase in Zn and K concentrations, the amount of nutrients including Na, Fe, Cu, Ca, Mn, and Mg decreased compared to the control level of Zn and K in nutrient solution except for Zn and K, which increased due to the Zn and K, respectively. Increased levels of Zn and K caused to decrease in malondialdehyde (MDA) content by 51% and 34%, respectively. Hydrogen peroxide (H2O2) was decreased also by 29% and 14% at 10 and 117 mg L- 1 concentration of Zn and K while higher levels of Zn and K in the nutrient solution, increased protein content by 1.4 and 1.2 folded compared to the control plants. The maximum activity of superoxide dismutase (SOD) was recorded in spinach treated with 10 mg L- 1 of Zn in combination independent to the K concentrations. The activity of ascorbate peroxidase (APX) was also affected by Zn as it showed up to 2.1 folded increment at 10 mg L- 1 Zn compared to the 0.22 mg L- 1 concentration. In general, an increase in Zn and K concentration in the nutrient solution decreased the absorption of measured nutrients except for Zn and K in spinach leaves. The effect of increased levels of Zn was more obvious than that of potassium in qualitative and biochemical traits of spinach specially at 5 mg L- 1 concentration. These findings suggest that supplementing hydroponic nutrient solutions with 5 mg L- 1 Zn in combination with 78 mg L- 1 K can lead to the better quality and tolerance of the plant, offering a promising strategy to enhance crop productivity and nutritional value in hydroponically cultivated spinach.

The implementation of the SPAD-502 Chlorophyll meter for the quantification of nitrogen content in Arabica coffee leaves

The utilization of a non-destructive SPAD-502 chlorophyll meter, which enables the measurement of nitrogen status in plant leaves, has gained popularity in agronomic crops. Its application to horticultural crops like coffee remains relatively uncommon. The device provides quick and real-time measurements, helping to provide on-time nitrogen fertilizer to coffee plants before deficiency signs occur. Coffee leaves are characterized by thick and waxy leaves, together with many layers of tree crown. Therefore, the objective of this study was to develop a method for measuring nitrogen levels in coffee plants using the SPAD-502 Chlorophyll meter for an appropriate nitrogen fertilizer application rate in Arabica coffee plants. •Coffee trees were separated into upper, middle and lower levels. Data on SPAD values and total nitrogen were analyzed.•Pearson Correlation Coefficient (R), Coefficient of Determination (R2) and linear regression were calculated for different three levels of both SPAD-502 and total nitrogen values.•The results revealed a strong correlation (R2 = 0.63) between the SPAD readings of coffee leaves obtained from the upper canopy and their nitrogen content. These findings can provide a good concept of which coffee crown level will be a better part for measuring N content using a SPAD-502 Chlorophyll meter.