NITROGENASE ACTIVITY OF COWPEA (Vigna unguiculata (L.) Walp.) DURING AND AFTER DROUGHT STRESS

1990 ◽  
Vol 70 (1) ◽  
pp. 163-171 ◽  
Author(s):  
S. PARARAJASINGHAM ◽  
D. P. KNIEVEL
Keyword(s):  
Drought Stress ◽  
Stomatal Conductance ◽  
Water Potential ◽  
Vigna Unguiculata ◽  
Nitrogenase Activity ◽  
Root Nodules ◽  
Experimental Period ◽  
Stress Recovery ◽  
Subsequent Recovery ◽  
Per Se

Greenhouse experiments were conducted with the objectives (1) to investigate the nitrogenase activity (NA) of cowpea (Vigna unguiculata (L.) Walp.) root nodules during the development of and subsequent recovery from drought stress and (2) to determine whether the changes in NA during and following drought stress are related to nodule water potential. Nitrogenase activity of root nodules decreased by more than 80% within 6–8 d of withholding water and recovered 1 or 2 d after watering. Nodule water potential declined significantly from approximately −0.2 MPa to −0.48 MPa with 8 d of stress and recovered to prestress levels within 24 h after watering. Midday abaxial stomatal conductance decreased significantly with stress but recovered within 24 h following watering. Midday leaf water potential did not change significantly during the experimental period. Nodule NA declined 2 d before that of nodule water potential in apparent response to declining soil water content. This response and the lag in the recovery of NA following drought stress after nodule water potential had returned to prestress levels support the hypothesis that nodule water potential per se is not the primary cause for the decline in NA of cowpea root nodules during drought stress.Key words: Vigna unguiculata (L.) Walp., nitrogenase activity, drought stress, recovery, cowpea

NITROGENASE ACTIVITY, PHOTOSYNTHESIS AND TOTAL NONSTRUCTURAL CARBOHYDRATES IN COWPEA DURING AND AFTER DROUGHT STRESS

1990 ◽  
Vol 70 (4) ◽  
pp. 1005-1012 ◽  
Author(s):  
S. PARARAJASINGHAM ◽  
D. P. KNIEVEL
Keyword(s):  
Drought Stress ◽  
Stomatal Conductance ◽  
Vigna Unguiculata ◽  
Nitrogenase Activity ◽  
Net Photosynthesis ◽  
Dry Weight ◽  
Plant Parts ◽  
Total Nonstructural Carbohydrates ◽  
Nonstructural Carbohydrate ◽  
And Control

Greenhouse experiments were conducted to determine whether depressed nitrogenase activity (NA) of cowpea (Vigna unguiculata (L.) Walp.) nodules during drought stress is associated with altered carbohydrate supply to the nodules. Nitrogenase activity of the nodules, midday abaxial stomatal conductance, leaf net photosynthesis and mg total nonstructural carbohydrate (TNC) g−1 dry weight of several plant parts were measured in cowpea subjected to and recovering from drought stress periods of 0, 4 and 8 days. In addition, cowpea plants were shaded or partially defoliated (75% leaf removal) to limit carbohydrate supply to the nodules of well-watered plants. Stomatal conductance, leaf net photosynthesis and nodule NA declined 60, 62 and 90%, respectively, within 4 d of withholding water. After 8 d of drought stress, leaf net photosynthesis and nodule NA were near zero. Stomatal conductance and leaf net photosynthesis returned to the level of unstressed plants within 24 h following rewatering while recovery of NA was delayed. Shading and defoliation of cowpea plants under well watered conditions decreased NA 62 and 44%, respectively. TNC concentrations of leaves, petioles, stems, roots and nodules did not differ appreciably between drought stressed and control plants. In contrast, TNC concentrations of shoot plant parts from shaded or defoliated plants declined significantly compared to controls and nodule TNC concentrations declined in shaded plants. The decline in NA by cowpea nodules during drought stress did not appear to be directly associated with carbohydrate supply to the nodules, but rather the result of a new equilibrium attained with overall limited plant growth under the stress.Key words: Vigna unguiculata (L.) Walp., nitrogenase activity, drought stress recovery, assimilate stress, shading, defoliation, total nonstructural carbohydrate

scholarly journals Arbuscular Mycorrhizal Fungi Inoculation as a Climate Adaptation Strategy for Establishment of Swietenia macrophylla King. Seedlings

Forests ◽  
2020 ◽  
Vol 11 (5) ◽  
pp. 488
Author(s):  
Lakshmy J. Rajan ◽  
Santhoshkumar A. V. ◽  
Surendra Gopal K. ◽  
Kunhamu T. K.
Keyword(s):  
Drought Stress ◽  
Stomatal Conductance ◽  
Arbuscular Mycorrhizal Fungi ◽  
Water Potential ◽  
Chlorophyll Content ◽  
Transpiration Rate ◽  
Mycorrhizal Fungi ◽  
Arbuscular Mycorrhizal ◽  
Tree Seedlings ◽  
Rate Of Photosynthesis

Research Highlights: Drought stress significantly decreased the performance of seedlings in the nursery. Seedlings inoculated with Claroideoglomus etunicatum is recommended to produce superior planting stock of mahogany seedlings with better drought resistance in the nursery. Background and Objectives: With numerous intense droughts across tropical regions due to climate change, it is crucial to understand effects of drought stress on tree seedlings to improve crop management practices and avoid failures on large scale planting. Swietenia macrophylla, a commercial timber species in India, is poorly studied in relation to its management including physiological responses to various environmental stresses. Arbuscular mycorrhizal fungi (AMF) is known to improve performance of tree seedlings under drought conditions and produce quality planting stock in nursery. This study aims to understand the responses of mahogany seedlings under different levels of drought stress when inoculated with three types of AMF, namely Funneliformis mosseae, Claroideoglomus etunicatum, and Rhizophagus intraradices. Materials and Methods: The experiment is conducted in pot culture using a factorial completely randomized design. Different irrigation regimes were applied at 100, 80, 60, and 40 percentage of weekly cumulative evapotranspiration. The seedlings were tested for biometric, physiological, and mycorrhizal parameters periodically. Results: Physiological attributes such as rate of photosynthesis, stomatal conductance, transpiration rate, chlorophyll content, and water potential were found to be higher in the daily irrigated (control) seedlings. Performance of the seedlings were poorest in the least irrigated treatment. It was apparent that inoculated seedlings performed better than the non-inoculated ones. Conclusions: Among the three different AMF species used, C. etunicatum was found to be the most beneficial and suitable for the young mahogany seedlings. These seedlings also recorded higher root colonization percentage and total spore count in the rhizosphere soils. Seedlings inoculated with C. etunicatum showed positive influence on rate of photosynthesis, stomatal conductance, transpiration rate, chlorophyll content, relative growth rate (RGR) and water potential of seedlings.

scholarly journals Effects of Engineered Sinorhizobium meliloti on Cytokinin Synthesis and Tolerance of Alfalfa to Extreme Drought Stress

2012 ◽  
Vol 78 (22) ◽  
pp. 8056-8061 ◽  
Author(s):  
Ji Xu ◽  
Xiao-Lin Li ◽  
Li Luo
Keyword(s):  
Nitrogen Fixation ◽  
Drought Stress ◽  
Sinorhizobium Meliloti ◽  
Nitrogenase Activity ◽  
Root Nodules ◽  
Severe Drought ◽  
Control Strain ◽  
Free Living ◽  
Content Type ◽  
Host Tolerance

ABSTRACTCytokinin is required for the initiation of leguminous nitrogen fixation nodules elicited by rhizobia and the delay of the leaf senescence induced by drought stress. A few free-living rhizobia have been found to produce cytokinin. However, the effects of engineered rhizobia capable of synthesizing cytokinin on host tolerance to abiotic stresses have not yet been described. In this study, two engineeredSinorhizobiumstrains overproducing cytokinin were constructed. The tolerance of inoculated alfalfa plants to severe drought stress was assessed. The engineered strains, which expressed theAgrobacterium iptgene under the control of different promoters, synthesized more zeatins than the control strain under free-living conditions, but their own growth was not affected. After a 4-week inoculation period, the effects of engineered strains on alfalfa growth and nitrogen fixation were similar to those of the control strain under nondrought conditions. After being subjected to severe drought stress, most of the alfalfa plants inoculated with engineered strains survived, and the nitrogenase activity in their root nodules showed no apparent change. A small elevation in zeatin concentration was observed in the leaves of these plants. The expression of antioxidant enzymes increased, and the level of reactive oxygen species decreased correspondingly. Although theiptgene was transcribed in the bacteroids of engineered strains, the level of cytokinin in alfalfa nodules was identical to that of the control. These findings suggest that engineeredSinorhizobiumstrains synthesizing more cytokinin could improve the tolerance of alfalfa to severe drought stress without affecting alfalfa nodulation or nitrogen fixation.

scholarly journals Effect of different soil water potential on leaf transpiration and on stomatal conductance in poinsettia

2013 ◽  
Vol 55 (2) ◽  
pp. 27-36
Author(s):  
Jacek S. Nowak
Keyword(s):  
Drought Stress ◽  
Stomatal Conductance ◽  
Water Potential ◽  
Soil Water ◽  
Soil Water Potential ◽  
Moisture Stress ◽  
Growing Period ◽  
High Soil Moisture ◽  
Cultivation Period ◽  
Leaf Transpiration

<i>Euphorbia pulcherrima</i> Wild.'Lilo' was grown in containers in 60% peat, 30% perlite and 10% clay (v/v) mixture, with different irrigation treatments based on soil water potential. Plants were watered at two levels of drought stress: -50kPa or wilting. The treatments were applied at different stages of plant development for a month or soil was brought to the moisture stress only twice. Additionally, some plants were watered at -50 kPa during the entire cultivation period while the control plants were watered at -5kPa. Plants were also kept at maximum possible moisture level (watering at -0,5kPa) or close to it (-1.OkPa) through the entire growing period. Soil water potential was measured with tensiometer. Drought stress applied during entire cultivation period or during the flushing stage caused significant reduction in transpiration and conductance of leaves. Stress applied during bract coloration stage had not as great effect on the stomatal conductance and transpiration of leaves as the similar stress applied during the flushing stage. High soil moisture increased stomatal conductance and transpiration rate, respectively by 130% and 52% (flushing stage), and 72% and 150% (bract coloration stage) at maximum, compared to the control.

scholarly journals Transpiration and Drought Stress Recovery of Three Zinnia Cultivars1

2018 ◽  
Vol 36 (3) ◽  
pp. 108-113
Author(s):  
Bruce R. Roberts ◽  
Chris Wolverton
Keyword(s):  
Drought Stress ◽  
Water Potential ◽  
Dry Weight ◽  
Zinnia Elegans ◽  
Stress Recovery ◽  
Xylem Water Potential ◽  
Horticultural Crops ◽  
Shoot Dry Weight ◽  
Stress Amelioration ◽  
Daily Transpiration

Abstract Transpiration and drought stress recovery were investigated in three container-grown zinnia cultivars [Zinnia elegans Jacq. (‘Lilliput' and ‘Thumbelina') and Z. haageana Reger (‘Persian Carpet')] by measuring daily changes in the normalized transpiration ratio (NTR) of well-watered (control), water-stressed, and water-stressed/re-watered plants. Transpiration of plants grown in gradually drying substrate did not decline until the fraction of transpirable substrate water (FTSW) reached 0.16 to 0.12. Symptoms of plant-water stress (i.e. foliar wilt) were first observed on the leaves of ‘Persian Carpet', which was also the cultivar with the highest average daily transpiration rate. By comparison, the remaining two cultivars (‘Lilliput' and ‘Thumbelina') exhibited lower average daily transpiration rates and took significantly longer to reach the same dry-down endpoint (NTR ≤0.15). Drought stress recovery was assessed by comparing xylem water potential and root and shoot dry weight in well-watered and in drought-stressed plants following a 7-day stress amelioration period. Xylem water potential of all three drought-stressed cultivars increased (i.e. became less negative) one week after re-watering. Root biomass and root:shoot ratio were both significantly greater in water-stressed plants than in well-watered plants of the same cultivar, a finding that suggests the likelihood of osmotic adjustment in response to drought. Index words: normalized transpiration ratio, fraction of transpirable substrate water, foliar wilt, containerized horticultural crops. Species used in this study: ‘Lilliput' and ‘Thumbelina' zinnia (Zinnia elegans Jacq.), ‘Persian Carpet' zinnia (Zinnia haageana Reger).

The decoupling between gas exchange and water potential of Cinnamomum camphora seedlings during drought recovery and its relation to ABA accumulation in leaves

2020 ◽  
Vol 13 (6) ◽  
pp. 683-692
Author(s):  
Honglang Duan ◽  
Defu Wang ◽  
Xiaohua Wei ◽  
Guomin Huang ◽  
Houbao Fan ◽  
...  
Keyword(s):  
Drought Stress ◽  
Stomatal Conductance ◽  
Gas Exchange ◽  
Water Potential ◽  
Stomatal Closure ◽  
Drought Severity ◽  
Physiology And Biochemistry ◽  
Drought Recovery ◽  
Moderate Drought ◽  
Rate Of Recovery

Abstract Aims Drought stress and the degree of drought severity are predicted to rise under highly variable patterns of precipitation due to climate change, while the capacity of trees to cope with drought recovery through physiological and biochemical adjustment remains unclear. We aimed to examine the coupling of physiology and biochemistry in trees during drought and the following recovery. Methods Potted seedlings of Cinnamomum camphora were grown under well watered conditions prior to the experimental drought stress, which was initiated by withholding water. Seedlings were rewatered following attainment of two drought severities: mild drought (stomatal closure) and moderate drought (ψxylem = −1.5 MPa). We measured leaf-level water potential, gas exchange (photosynthesis and stomatal conductance), abscisic acid (ABA), proline and non-structural carbohydrates (NSCs) concentrations in seedlings of C. camphora during drought and a 4-day recovery. Important Findings We found that drought severity largely determined physiological and biochemical responses and affected the rate of recovery. Stomatal closure occurred at the mild drought stress, accompanied with ABA accumulation in leaves and decline in water potential, while leaf proline accumulation and variable NSC were evident at the moderate drought stress. More severe drought stress led to delayed recovery of gas exchange, but it did not have significant effect on water potential recovery. The relationships of water potential and gas exchange differed during drought stress and post-drought recovery. There was tight coupling between water potential and gas exchange during drought, but not during rewatering due to high ABA accumulation in leaves, thereby delaying recovery of stomatal conductance. Our results demonstrate that ABA could be an important factor in delaying the recovery of stomatal conductance following rewatering and after water potential recovery of C. camphora. Furthermore, greater drought severity had significant impacts on the rate of recovery of tree physiology and biochemistry.

The Effects of Drought on Leaf Gas Exchange and Growth of Three Species of Herbaceous Perennials

HortScience ◽  
1998 ◽  
Vol 33 (3) ◽  
pp. 540a-540
Author(s):  
K.J. Prevete ◽  
R.T. Fernandez
Keyword(s):  
Drought Stress ◽  
Stomatal Conductance ◽  
Gas Exchange ◽  
Drought Tolerance ◽  
Transpiration Rate ◽  
Leaf Gas Exchange ◽  
Gas Analysis ◽  
Herbaceous Perennials ◽  
Effects Of Drought ◽  
Analysis System

Three species of herbaceous perennials were tested on their ability to withstand and recover from drought stress periods of 2, 4, and 6 days. Eupatorium rugosum and Boltonia asteroides `Snowbank' were chosen because of their reported drought intolerance, while Rudbeckia triloba was chosen based on its reported drought tolerance. Drought stress began on 19 Sept. 1997. Plants were transplanted into the field the day following the end of each stress period. The effects of drought on transpiration rate, stomatal conductance, and net photosynthetic rate were measured during the stress and throughout recovery using an infrared gas analysis system. Leaf gas exchange measurements were taken through recovery until there were no differences between the stressed plants and the control plants. Transpiration, stomatal conductance, and photosynthesis of Rudbeckia and Boltonia were not affected until 4 days after the start of stress. Transpiration of Eupatorium decreased after 3 days of stress. After rewatering, leaf gas exchange of Boltonia and Rudbeckia returned to non-stressed levels quicker than Eupatorium. Growth measurements were taken every other day during stress, and then weekly following transplanting. Measurements were taken until a killing frost that occurred on 3 Nov. There were no differences in the growth between the stressed and non-stressed plants in any of the species. Plants will be monitored throughout the winter, spring, and summer to determine the effects of drought on overwintering capability and regrowth.

scholarly journals Candidate genes and SNPs associated with stomatal conductance under drought stress in Vitis

2021 ◽  
Vol 21 (1) ◽  
Author(s):  
Massimiliano Trenti ◽  
Silvia Lorenzi ◽  
Pier Luigi Bianchedi ◽  
Daniele Grossi ◽  
Osvaldo Failla ◽  
...  
Keyword(s):  
Drought Stress ◽  
Stomatal Conductance ◽  
Candidate Genes ◽  
Water Deficit ◽  
Genetic Basis ◽  
Phenotypic Diversity ◽  
Snp Array ◽  
A Genome ◽  
Raffinose Synthase ◽  
Response To Water

Abstract Background Understanding the complexity of the vine plant’s response to water deficit represents a major challenge for sustainable winegrowing. Regulation of water use requires a coordinated action between scions and rootstocks on which cultivars are generally grafted to cope with phylloxera infestations. In this regard, a genome-wide association study (GWAS) approach was applied on an ‘ad hoc’ association mapping panel including different Vitis species, in order to dissect the genetic basis of transpiration-related traits and to identify genomic regions of grape rootstocks associated with drought tolerance mechanisms. The panel was genotyped with the GrapeReSeq Illumina 20 K SNP array and SSR markers, and infrared thermography was applied to estimate stomatal conductance values during progressive water deficit. Results In the association panel the level of genetic diversity was substantially lower for SNPs loci (0.32) than for SSR (0.87). GWAS detected 24 significant marker-trait associations along the various stages of drought-stress experiment and 13 candidate genes with a feasible role in drought response were identified. Gene expression analysis proved that three of these genes (VIT_13s0019g03040, VIT_17s0000g08960, VIT_18s0001g15390) were actually induced by drought stress. Genetic variation of VIT_17s0000g08960 coding for a raffinose synthase was further investigated by resequencing the gene of 85 individuals since a SNP located in the region (chr17_10,497,222_C_T) was significantly associated with stomatal conductance. Conclusions Our results represent a step forward towards the dissection of genetic basis that modulate the response to water deprivation in grape rootstocks. The knowledge derived from this study may be useful to exploit genotypic and phenotypic diversity in practical applications and to assist further investigations.

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