Influence of drought on the photosynthetic apparatus activity, senescence rate, and productivity in wheat plants

Effects of soil drought at flowering stage on the functional state of photosynthetic apparatus and chloroplast enzymatic antioxidant defense systems in flag leaf during reproductive period, and the productivity of winter wheat plants of high-protein Natalka variety and drought-tolerant Podolyanka variety were studied in pot experiment. Until flowering and for the control plants during the entire vegetation, the soil moisture content was maintained at a level of 60—70 % of field capacity (FC). Drought treatment (soil moisture 30 % FC) was applied for 7 days covering flowering—early kernel watery ripe period (BBCH 61—71). After that, watering of plants was resumed to a control level which was maintained until the end of the growing season. The estimation of the chlorophyll and Rubisco content, the chloroplast antioxidant enzymes activity, and the net CO2 assimilation and transpiration rates was carried out on flag leaves. The measurements were taken on the third day of watering cessation (the first day the soil moisture reached 30 % FC, BBCH 61), at the end of the drought period (seventh day at 30 % FC, BBCH 71), and after watering resumed at the medium milk (BBCH 75) and late milk (BBCH 77) stages. The components of plant grain productivity were determined by weighing air-dry material at grain full ripeness. It was revealed, that drought stress during flowering inhibited CO2 assimilation and accelerated induction of senescence processes in wheat plants associated with degradation of photosynthetic apparatus and manifested in quicker ontogenetic drop in chlorophyll and Rubisco contents and loss of leaf photosynthetic activity. This exacerbated the drought impact on the plant organism so that after optimal watering return, the physiological and biochemical parameters were not restored to the values of control plants that were all time under optimal moisture supply. Stress-induced premature senescence reduced the supply of plants with assimilates and ultimately led to a decrease in their grain productivity. Impact of drought on flag leaf photosynthetic activity and especially on senescence induction were much more pronounced in the high-protein wheat variety Natalka with a genetically programmed earlier start of the nitrogen-containing compounds remobilization from leaves than in Podolyanka variety. The drought-tolerant variety Podolyanka keep ability to maintain much higher CO2 assimilation activity during drought period and to preserve photosynthetic apparatus from early induction of senescence due to likely more efficient chloroplast antioxidant defense systems, thereby gaining a better assimilates supply for yield formation.

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Effects of drought at different periods of wheat development on the leaf photosynthetic apparatus and productivity

Regulatory Mechanisms in Biosystems ◽

10.15421/021961 ◽

2019 ◽

Vol 10 (4) ◽

pp. 406-414

Author(s):

V. V. Morgun ◽

O. O. Stasik ◽

D. A. Kiriziy ◽

O. G. Sokolovska-Sergiienko ◽

N. M. Makharynska

Keyword(s):

Soil Moisture ◽

Chlorophyll Content ◽

Stem Elongation ◽

Flag Leaf ◽

Photosynthetic Apparatus ◽

Field Capacity ◽

Crop Productivity ◽

Drought Treatment ◽

Drought Impact ◽

Grain Productivity

The problem of drought impact on crop productivity is especially relevant for the leading cereal – wheat, since significant cultivation areas of this crop are located in risky farming zones. The aim of our studies was to compare the peculiarities of drought impact during the period of vegetative growth and reproductive development on the chlorophyll content, activity of chloroplast antioxidant enzymes, the rate of carbon dioxide gas exchange and transpiration as well as productivity of the wheat plants. The studies were carried out on bread winter wheat plants (Triticum aestivum L.) of the Astarta and Natalka varieties grown in a pot experiment. The plants were watered daily to maintain the soil moisture level in the pots in the range 70–60% of field capacity. Drought treatment involving decrease in soil moisture to 30% of the field capacity was applied to some of the plants at late stem elongation stage (BBCH 37-45) and to other plants at heading-anthesis (BBCH 59-65) while control plants were watered as usual. After 7 days of drought, the watering of treated plants was resumed to maintain the soil moisture at the level of control plants until the harvest. The penultimate leaf at the late stem elongation stage and flag leaf at the heading–anthesis period were used for measurements of photosynthetic apparatus response to drought. Plants of both varieties treated at stem elongation stage showed lower decline in the photosynthetic activity, chlorophyll content and grain productivity than those treated at heading-anthesis. The results obtained indicated that photosynthetic apparatus of wheat has a higher drought tolerance at the stem elongation stage than during the heading-anthesis stage. Furthermore, plants stressed at the stem elongation stage revealed better compensatory growth of lateral productive shoots due to superior supply of plants with assimilates after drought termination. Astarta variety had a more drought-tolerant photosynthetic apparatus and higher grain productivity in both well-watered and drought conditions as compared to Natalka variety. The differences between varieties were more contrasting when drought was applied at heading-anthesis.

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Effect of drought on photosynthetic apparatus, activity of antioxidant enzymes, and productivity of modern winter wheat varieties

Regulatory Mechanisms in Biosystems ◽

10.15421/021903 ◽

2019 ◽

Vol 10 (1) ◽

pp. 16-25 ◽

Cited By ~ 1

Author(s):

V. V. Morgun ◽

O. O. Stasik ◽

D. A. Kiriziy ◽

O. G. Sokolovska-Sergiienko

Keyword(s):

Antioxidant Enzymes ◽

Soil Moisture ◽

Drought Tolerance ◽

Winter Wheat ◽

Flag Leaf ◽

Co2 Assimilation ◽

Assimilation Rate ◽

Wheat Varieties ◽

Grain Productivity ◽

Winter Wheat Varieties

The response of modern winter wheat varieties to soil drought was studied with aim of phenotyping their drought tolerance characteristics and identification of the most informative indices that may be suitable for use in breeding programs. Plants of winter bread wheat (Triticum aestivum L.) varieties Podolyanka, Khurtovyna, Vinnychanka and Prydniprovska were grown in a pot experiment. The soil moisture for control plants was maintained at a level of 70% of field capacity (FC) throughout the vegetative stage. At the flowering, watering of the treated plants was stopped to reduce the soil moisture to a level of 30% FC and then this soil moisture level was maintained for 10 days. After that, the irrigation of the treated plants was restored to the level of control. It was found that in the flag leaf under drought condition, the chlorophyll content, net CO2 assimilation rate, and transpiration rate decreased, while the leaf water deficit, the ratio of photorespiration to CO2 assimilation, and the activity of chloroplasts antioxidant enzymes (superoxide dismutase and ascorbate peroxidase) increased. The ten-day drought significantly reduced the grain yield from the plant. Calculations of the relative changes in the physiological parameters of treated plants as compared to the control were the most informative for the differentiation of varieties for drought tolerance. Relative changes in the content of chlorophyll in the flag leaf under drought and reduction in the total biomass of the plant closely correlated with a decrease in grain productivity (r = 0.92 and r = 0.96 respectively). There was also a significant correlation of grain productivity with a decrease in the NAR measured in the period of drought (r = 0.68). Therefore, the maintenance of the photosynthetic function of plants under conditions of insufficient water supply plays a determinant role in reducing the grain productivity losses. The relative changes in the chlorophyll content and CO2 assimilation rate in plants subjected to drought as compared to control may be used as markers of drought tolerance of genotypes for genetic improvement of wheat by conventional breeding and biotechnological methods.

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Fractal and Topological Analyses and Antioxidant Defense Systems of Alfalfa (Medicago sativa L.) Root System under Drought and Rehydration Regimes

Agronomy ◽

10.3390/agronomy10060805 ◽

2020 ◽

Vol 10 (6) ◽

pp. 805 ◽

Cited By ~ 1

Author(s):

Shuo Li ◽

Liqiang Wan ◽

Zhongnan Nie ◽

Xianglin Li

Keyword(s):

Soil Moisture ◽

Medicago Sativa ◽

Antioxidant Defense ◽

Root Systems ◽

Water Holding Capacity ◽

Defense Systems ◽

Antioxidant Defense Systems ◽

Medicago Sativa L ◽

Moisture Conditions ◽

Water Holding

Alfalfa (Medicago sativa L.) is a nutritious forage plant in dryland regions with strong drought tolerance and broad adaptability. To understand the architectural characters and physiological functions of the root systems in response to different drought stress and rehydration, two experiments were conducted in a glasshouse. Experiment 1 used three alfalfa cultivars and four soil moisture treatments in a split-plot design with four replicates to investigate the response of root systems of different alfalfa cultivars to drought stress and subsequent rehydration. Experiment 2 used one alfalfa cultivar and four soil moisture treatments in a randomized complete block (RCB) design with three replicates to measure reactive oxidant species and antioxidant defense systems of alfalfa root. The soil moisture treatments included (1) 75–80% of the water-holding capacity (CK); (2) 60–65% of the water-holding capacity and subsequent rehydration to 75–80% of the water-holding capacity; (3) 45–50% of the water-holding capacity and subsequent rehydration to 60–65% and 75–80% of the water-holding capacity; and (4) 30–35% of the water-holding capacity and subsequent rehydration to 45–50%, 60–65% and 75–80% of the water-holding capacity. Our results demonstrated that plants had higher root biomasses (mean = 0.77 g), fractal dimensions (1.47), fractal abundances (3.84), and branching ratios (0.39) under severe water deficit and rehydration than under less stressful soil moisture conditions. Plant root systems tended to exhibit herringbone branching (Topological Index = 0.63) when soil moisture was at 60–65% water-holding capacity with the soil being then rehydrated, whereas they tended to have a smaller lateral root length, root surface area, root volume, and branching ratio and larger root diameter under more favorable soil moisture conditions for less stressful soil moisture treatments. Severe water stress and subsequent considerably improved superoxide (O2−) generation rate, the content of hydrogen peroxide (H2O2) and Malondialdehyde (MDA), and non-enzyme antioxidant glutathione (GSH), and reduced the content of ascorbate (AsA) and activity of catalase (CAT), ascorbate peroxidase (APX), and glutathione peroxidase (GPX). It is concluded that Medicago sativa L. cv Zhaodong (ZD) and cv Aohan (AH) exhibited higher drought resistances than cv Golden empress (GE) using topological and fractal analyses. This could be a key contributor to altering optimum soil moisture conditions and screening alfalfa cultivars based on root system architecture and antioxidant defense systems. The molecular functions warrant further investigation which could help explain the observed root phenotypes after drought conditions and rehydration.

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