Increase In Moisture Stress Research Articles

Modeling tree radial growth in a warming climate: where, when, and how much do potential evapotranspiration models matter?

Process-based models of tree-ring width are used both for reconstructing past climates and for projecting changes in growth due to climate change. Since soil moisture observations are unavailable at appropriate spatial and temporal scales, these models generally rely on simple water budgets driven in part by temperature-based potential evapotranspiration (PET) estimates, but the choice of PET model could have large effects on simulated soil moisture, moisture stress, and radial growth. Here, I use four different PET models to drive the VS-Lite model and evaluate the extent to which they differ in both their ability to replicate observed growth variability and their simulated responses to projected 21st century warming. Across more than 1200 tree-ring width chronologies in the conterminous United States, there were no significant differences among the four PET models in their ability to replicate observed radial growth, but the models differed in their responses to 21st century warming. The temperature-driven empirical PET models (Thornthwaite and Hargreaves) simulated much larger warming-induced increases in PET and decreases in soil moisture than the more physically realistic PET models (Priestley–Taylor and Penman–Monteith). In cooler and more mesic regions with relatively minimal moisture constraints to growth, the models simulated similarly small reductions in growth with increased warming. However, in dry regions, the Thornthwaite- and Hargreaves-driven VS-Lite models simulated an increase in moisture stress roughly double that of the Priestley–Taylor and Penman–Monteith models, which also translated to larger simulated declines in radial growth under warming. While the lack of difference in the models’ ability to replicate observed radial growth variability is an encouraging sign for some applications (e.g. attributing changes in growth to specific climatic drivers), the large differences in model responses to warming suggest that caution is needed when applying the temperature-driven PET models to climatic conditions with large trends in temperature.

Biochemical responses of Moringa oleifera Lam. plants to graded moisture deficit

Continual water loss through transpiration and evaporation as a result of drought leads to stomatal closure and subsequently the overproduction of reactive oxygen species (ROS) which causes oxidative stress in plants. A set of biochemical mechanisms are concurrently triggered to set in motion a defence line, which, among others, involves the synthesis of antioxidant and osmoprotectants compounds. These play a protective role to overcome stress. The objective of this study was to evaluate the effect of varying moisture regimes on the accumulation patterns and concentration of phenolic compounds, antioxidant activity and osmolyte proline in Moringa oleifera. The study was conducted in a greenhouse (25 ± 3°C) at ARC, Roodeplaat in Pretoria, South Africa. Moringa oleifera seeds were individually planted in pots using hygro-mix as the growth media. The experiment was laid out in a completely randomised design with four watering regimes of 100%, 75%, 50% and 35% field water capacity (FWC) each with 50 replicate plants. Proline content increased with the severity of moisture stress in all plant parts (root, stem and leaf), with the leaves under severe stress (35% FWC) recording the highest concentration. Folin C, aluminium chloride and butanol-HCL assays were used to determine total phenolic, flavonoid and condensed tannin concentrations, respectively, in the different plant parts at different growth stages and harvests. The concentrations of these secondary metabolites were consistently higher in leaves and increased with an increase in moisture stress. The highest concentrations were recorded in the second harvest under severe stress (35% FWC) for total phenolics and proanthocyanidins at 50% FWC for flavonoids . Leaves showed a better antioxidant ability and antioxidant activities increased with drought progression as determined by FRAP while DPPH radical scavenging and the β-carotene-linoleic acid model system did not show a distinct trend in antioxidant activities in relation to the different moisture levels. Based on the results of this study, antioxidant and osmoprotectant compounds as well as antioxidant activity appears to increase corresponding to severity of moisture stress in all plant parts at both harvests. This trend suggests that M. oleifera employs these mechanisms in adapting to moisture stress.

Morphological, Physiological and Biochemical evaluation of transgenic green gram (Vigna radiata L. Wilczek) for drought tolerance

Green gram (Vigna radiata L. Wilczek) is one of the important pulse crops in India belongs to the family Fabaceae. The production and productivity is severely affected by abiotic stresses like drought and salinity. Both control and transformed plants of green gram variety ‘IPM-02-03’ were evaluated for moisture stress. Soil moisture stress was imposed at the reproductive stage by withholding irrigation completely for 7 days. Morphological, physiological and biochemical parameters were evaluated for drought tolerance at 0th, 3rd and 7th days with 100%, 50% and 25% water holding capacity, respectively during drought stress. In almost all the cases under moisture stress, transgenic plants showed higher yield and 100 seed weight. Pigments like chlorophyll and carotenoids accumulation was drastically decreases with increase in moisture stress. Higher accumulation of proline and antioxidant enzymes in transgenic plants than control showed better survival in stress condition. The present study suggests that, over expression of TIP1 gene in transformed plant can enhance better survival under drought stress condition.

Response of Albizia lebbeck to Moisture Stress on Seed Germination and Moisture Gradient on Seedling Growth

The polyethylene glycol (PEG 6000) was used under laboratory conditions. The studied parameters viz., germination percentage, mean daily germination, peak value, germination value and hypocotyls length was significantly reduced with increase in moisture stress. The control treatment T1 had highest Germination percentage, mean daily germination, peak value, and germination value and hypocotyls length. There were decreases in the values of all the studied germination parameters with increase in moisture stress created by use of different concentration of polyethylene glycol (PEG 6000). The different irrigation interval (days) followed for seedling production in nursery exhibited that different moisture gradients in nursery soil effected significantly seedling growth parameters viz., seedling height, collar diameter, number of leaves, leaf area, number, fresh shoot weight, fresh root weight, chlorophyll a content, chlorophyll b content, nutrient uptake in leafs (N,P,K) and root: shoot ratio were significant. There was decrease in all the studied growth parameters (except root shoot ratio) recorded with increase in moisture stress caused by irrigation interval studied. Out of the three container size of hyco-trays studied, the container size T3 (300 cc) had significantly the highest seedling height, collar diameter, number of leaves, leaf area, fresh shoot weight, fresh root weight, total chlorophyll, nitrogen content in leaf, phosphorus content in leaf, potassium content in leaf and root; shoot ratio as compared to container size T1 (93 cc) and T2 (150 cc).There were increase in all the studied growth parameters (except root shoot ratio) studied with increase in size of root containers, which could be attributed to more growing media and nutrients, and higher water holding capacity in large sized containers.

Normalized Sunlit Shaded Index (NSSI) for characterizing the moisture stress in wheat crop using classified thermal and visible images

Abstract In this study, we used proximal thermal and visible imaging system to separate four different components of the wheat crop, i.e., canopy and soil under sunlit and shaded conditions using Support Vector Machine method of supervised image classification approach under different moisture stress treatments. A Normalized Sunlit Shaded Index (NSSI) was developed to characterize the status of the wheat crop grown under moisture stress conditions at different growth stages. Results demonstrated that Thermal image-based NSSI (TI-NSSI) had the best correlations with all the measured crop biophysical parameters than the visible image (VI-NSSI). However, the r2 decreased with an increase in moisture stress. Among the different biophysical parameters tested in this study, TI-NSSI showed the highest significant negative correlation (−0.962***) with Radiation use efficiency (RUE). In general, irrespective of the moisture stress VI-NSSI gave the least relationship with all the biophysical parameters tested. Further regression analysis showed that TI-NSSI could explain the variations in RUE under different moisture stress conditions with R2 > 0.960. Regression analysis with yield showed that TI-NSSI under peak vegetative growth stage (83 DAS) adequately captured the variations in crop yield under moisture stress conditions.

Screening of Rice Apoplast Associated Endophytic Bacterial Isolates for Moisture Stress Tolerance and Plant Growth Promoting Traits

Investigations were made to identify, screen and characterize rice apoplastic fluid endophytic bacterial strains for osmotic stress tolerance and plant growth promoting activity. These bacterial strains were identified phylogentically as Bacillus subtilis TSAC5, Bacillus subtilis TSAA2, Bacillus sp. R2AA10, Bacillus cereus R2AA7, Bacillus marisflavi TSAC7, Cupriavidus alkaliphilus TSAC1, Delftia sp. TSAC2, Janibacter melonis R2AA1, Microbacterium oleivorans R2AA6, Kocuria rosea R2AA5, Pseudomonas aeruginosa NAAI3 and Sphingobium yanoikuyae R2AI1. Of these 12 strains, eight were obtained from drought tolerant rice varieties such as Anna R4 and IR DRT 64 and four from normal rice variety CO51. These endophytes exhibited varied level of osmotic stress tolerance created using different concentrations of PEG 6000 (-1.5, -3.0, -4.0, -4.5, -5.0 and -5.5 MPa) under in vitro conditions in liquid and solid medium. Among the 12 strains, Cupriavidus alkaliphilus TSAC1, Delftia sp. TSAC2, Bacillus marisflavi TSAC7, Janibacter melonis R2AA1, Kocuria rosea R2AA5, Pseudomonas aeruginosa NAAI3 and Sphingobium yanoikuyae R2AI1 showed moisture stress tolerance up to -5.5 MPa. Further increase in moisture stress of -6.0 MPa inhibited growth of 12 tested strains. These strains also exhibited Indole acetic acid (IAA), gibberellic acid (GA3) and extracellular polysaccharide (EPS) production and also showed ACC deaminase (ACCD) activity. Maximum extracellular proline production was found in Bacillus marisflavi TSAC7 under both normal and water stressed conditions. Higher IAA productivity was registered in Janibacter melonis R2AA1 followed by Cupriavidus alkaliphilus TSAC1 and Sphingobium yanoikuyae R2AI1 in the absence of PEG 6000. In the presence of PEG 6000 Delftia sp. TSAC2 recorded maximum IAA productivity. Bacillus subtilis TSAA2 showed greater ACC deaminase activity. EPS production was in the order of Pseudomonas aeruginosa NAAI3 followed by Sphingobium yanoikuyae R2AI1. Sphingobium yanoikuyae R2AI1 produced maximum quantity of GA3 both under normal and water stressed condition. None of the tested strains indicated insoluble phosphate, silicate and zinc solubilisation.

Compositional response of Amazon forests to climate change.

Most of the planet's diversity is concentrated in the tropics, which includes many regions undergoing rapid climate change. Yet, while climate‐induced biodiversity changes are widely documented elsewhere, few studies have addressed this issue for lowland tropical ecosystems. Here we investigate whether the floristic and functional composition of intact lowland Amazonian forests have been changing by evaluating records from 106 long‐term inventory plots spanning 30 years. We analyse three traits that have been hypothesized to respond to different environmental drivers (increase in moisture stress and atmospheric CO 2 concentrations): maximum tree size, biogeographic water‐deficit affiliation and wood density. Tree communities have become increasingly dominated by large‐statured taxa, but to date there has been no detectable change in mean wood density or water deficit affiliation at the community level, despite most forest plots having experienced an intensification of the dry season. However, among newly recruited trees, dry‐affiliated genera have become more abundant, while the mortality of wet‐affiliated genera has increased in those plots where the dry season has intensified most. Thus, a slow shift to a more dry‐affiliated Amazonia is underway, with changes in compositional dynamics (recruits and mortality) consistent with climate‐change drivers, but yet to significantly impact whole‐community composition. The Amazon observational record suggests that the increase in atmospheric CO 2 is driving a shift within tree communities to large‐statured species and that climate changes to date will impact forest composition, but long generation times of tropical trees mean that biodiversity change is lagging behind climate change.

Germination Biology of Sesbania (Sesbania cannabina): An Emerging Weed in the Australian Cotton Agro-environment

AbstractSesbania [Sesbania cannabina(Retz.) Pers.] is a problematic emerging weed species in Australian cotton-farming systems. However, globally, no information is available regarding its seed germination biology, and better understanding will help in devising superior management strategies to prevent further infestations. Laboratory and glasshouse studies were conducted to evaluate the impact of various environmental factors such as light, temperature, salt, osmotic and pH stress, and burial depth on germination and emergence of two Australian biotypes ofS. cannabina. Freshly harvested seeds of both biotypes possessed physical dormancy. A boiling-water scarification treatment (100±2 C) of 5-min duration was the optimum treatment to overcome this dormancy. Once dormancy was broken, the Dalby biotype exhibited a greater germination (93%) compared with the St George biotype (87%). The nondormant seeds of both biotypes showed a neutral photoblastic response to light and dark conditions, with germination marginally improved (6%) under illumination. Maximum germination of both biotypes occurred under an alternating temperature regime of 30/20 and 35/25 C and under constant temperatures of 32 or 35 C, with no germination at 8 or 11 C. Seed germination of both biotypes decreased linearly from 87% to 14% with an increase in moisture stress from 0.0 to −0.8 MPa, with no germination possible at −1.0 MPa. There was a gradual decline in germination for both biotypes when imbibed in a range of salt solutions of 25 to 250 mM, with a 50% reduction in germination occurring at 150 mM. Both biotypes germinated well under a wide range of pH values (4.0 to 10.0), with maximum germination (94%) at pH 9.0. The greatest emergence rate of the Dalby (87%) and St George (78%) biotypes was recorded at a burial depth of 1.0 cm, with no emergence at 16.0 cm. Deep tillage seems to be the best management strategy to stopS. cannabina’s emergence and further infestation of cotton (Gossypium hirsutumL.) fields. The findings of this study will be helpful to cotton agronomists in devising effective, sustainable, and efficient integrated weed management strategies for the control ofS. cannabinain cotton cropping lands.

Physiological Studies on Moisture Stress Tolerance in Chickpea (Cicer Arietinum L.) Genotypes

Drought is a major constraint that limits seed yield in chickpea (Cicer arietinum L.). It is important to establish the relative importance many of these drought-related traits for prioritizing their consideration in breeding for drought tolerance improvements. The objective of this study was to categorize the drought tolerant and susceptible chickpea genotypes on the basis of physiological parameters. An experiment was conducted with five chickpea genotypes in field under irrigated and rain fed conditions. Observations were recorded on relative water content (RWC), and the contents of chlorophyll (Chl), carotenoid (Car), proline (Pro) and protein in the five chickpea genotypes. RWC and contents of Chl, Car and protein decreased under moisture stress, whereas Pro content increased with the increase in moisture stress. Pusa-1108, Pusa-362, Pusa-1103 were able to maintain relatively higher RWC, Chl, Car and protein content and greater Pro accumulation, while Flip 90-166 and SBD- 377 showed comparatively greater decline in the RWC, Chl, Car and Protein and less accumulation of Pro under moisture stress. The data suggest that chickpea genotypes can be categorized into drought tolerant and susceptible types based on the variations in RWC, Chl, Car, Pro and protein content.

Osmotic Adjustment in Wheat in Relation to Grain Yield under Water Deficit Environments

Six greenhouse and three field experiments were conducted at the International Center for Improvement of Maize and Wheat (CIMMYT), Mexico, on bread wheat (Triticum aestivum L.) genotypes to ascertain the role of osmotic adjustment (OA) in sustaining grain yield and its stability under water deficit conditions. Under simulated water deficit conditions of the greenhouse and field, the genotypes differed considerably regarding OA, ranging from 0.31 to 0.86 MPa and from 0.60 to 0.99 MPa, respectively. When the mean values of OA across the six greenhouse experiments were regressed against those of grain yield obtained at different moisture levels of the line source, the correlation coefficient value increased with the increase in moisture stress, turning positively significant (P < 0.001) at the highest water deficit level. Similarly, osmotic potential at full turgor (OP100) and turgor potential (TP), measured in the greenhouse, were positively correlated (P < 0.05) with grain yield at the highest line source water deficit level. Osmotic adjustment and grain yield, both measured in the simulated water deficit condition in the field, were also positively correlated (P < 0.05). Besides, OA maintained yield stability through maintenance of turgor under water deficit during reproductive period of crop growth. The heritability of OA, OP100, and TP, computed by pooled analysis of variance across the six greenhouse experiments, was 0.74, 0.73, and 0.79, respectively. The results indicated that OA, as well as OP100 and TP, could be used as screening tools for drought‐resistant bread wheat genotypes in the greenhouse. This study also demonstrated the appropriate greenhouse screening methodology in this regard.

Efecto de los niveles de humedad y tasas de fósforo sobre la absorción de fósforo y el crecimiento del maíz

Se evaluó el efecto del contenido de humedad del suelo y aplicaciones de fósforo en el crecimiento del maíz (Zea mays L.) y la absorción de P en un experimento de tiestos bajo condiciones de invernadero. Los suelos incluidos en el estudio fueron Lewisburg (arenáceo, mixto, mésico, Typic Hapludalf) y Nipe (arcilloso, oxídico, isohipertérmico, Anionic Acrudox). Los niveles de humedad evaluados fueron M5 = capacidad de campo, M2 = fluctuación entre la capacidad de campo y 50% agua disponible y M3 = fluctuación entre la capacidad de campo y el punto de marchitez. Los niveles de fósforo fueron: P1 = 0 kg. P/ha., P2 = 112 kg. P/ha. y P3 = 224 kg. P/ha. Las aplicaciones de P aumentaron significativamente los pesos fresco y seco de las plantas de maíz sembradas en el suelo Lewisburg. El tratamiento de capacidad de campo (M1) superó significativamente o los tratamientos M2 y M3 en pesos fresco y seco cuando se aplicó 112 kg. de P/ha. al suelo Lewisburg. Al aumentar la aplicación de P a 224 kg. de P/ha. no se observó diferencia significativa entre M1 y M2, pero ambos tratamientos de humedad fueron significativamente superiores al M3 . Las plantas de maíz sembradas en el suelo Nipe no mostraron respuesta significativa a los tratamientos de P o humedad del suelo. Las aplicaciones de fósforo de 0, 112 y 224 kg./ha, al suelo Lewisburg resultaron en una absorción de P de 3.89, 21.60 y 42.73 mg./tiesto, respectivamente. La disminución en el contenido de agua disponible en el suelo redujo la absorción de P. La absorción de P correspondiente a los tratamientos M1, M2 y M3 fue 27.88, 22.91 y 17.42 mg./tiesto, respectivamente. El maíz en el suelo Nipe aumentó la absorción de P de 0.82 a 1.24 mg./tiesto al aumentar la aplicación de 112 a 224 kg. P/ha. Sin embargo, la diferencia en absorción no fue estadísticamente significativa. Tampoco se observó ningún efecto de los tratamientos de humedad en la absorción de P en este suelo. La poca fertilidad del suelo Nipe, así como una alta capacidad para adsorber P pueden haber contribuido a la ausencia de una respuesta significativa a los tratamientos evaluados.

Sensing of moisture stress effects by infra-red thermometry in sorghum, maize and pearl millet

Field experiment was carried out on sandy loam soil with sorghum (cv. S-136), maize (cv. Ageti-76) and pearl millet (cv. PHB-14) during the summer season (may–July) of 1980 at Haryana Agricultural University Farm, Hisar. After one uniform irrigation at crop establishment, the crops were subjected to four irrigation treatments, viz. irrigation at ID/CPE (ID=irrigation depth of 7cm; CPE=cumulative pan evaporation) of 1.0, 0.6, 0.3 & 0.15. Changes in soil water potential (ψ soil), leaf water potential (ψ L), stomatal conductance (KL), canopy temperature (Tc), transpirational cooling (Canopy temperature minus air temperature, Tc-Ta), evapotranspiration (ET) and dry matter yields were recorded in different treatments. An increase in moisture stress resulted in a decrease in ψ soil, ψ L, KL, transpirational cooling, ET but increase in Tc. Tc-Ta showed significant curvilinear association with ψ soil and linear relationship with ψ L, KL, Tc, ET and dry matter yield of summer cereals. It is suggested that the mid day values of Tc-Ta as observed with an infra-red thermometer could effectively be used to sense the moisture stress effects in summer cereals.

Effect of Leaf Area, Incident Radiation, and Moisture Stress on Reflectance of Near Infrared Radiation from a Corn Canopy1

AbstractPlant moisture stress is a major limiting factor in crop production. Remote sensing of moisture stress in crops would allow definition of the environmental conditions causing stress and timely use of management practices to avoid it. The reflectance of solar radiation, however, may be more affected by plant cover and meteorological factors than by moisture stress. The objectives of this research were to monitor continuously incident near infrared radiation (IR ↓) and reflectance (IR ↑ ) from corn (Zea mays L.) and to relate the reflectance ratio (IR ↑ /IR ↓ ) to green leaf area index (LAI), IR ↓ , and moisture stress indices. The experiment was conducted at West Lafayette, Indiana on a Typic Argiaquoll (Chalmers silt loam) in 1973 and 1974 and on dune sand in 1975 and 1976. Under non‐moisture stress (ns) conditions, LAI was used in a function (FLAI) to identify the ratio of green plant cover (RGPC). Linear regressions showed that as FLAI or RGPC increased from 0 to 1, (IR ↑ /IR ↓ )‐ increased an average of 9%. For each cal cm‐2 hr‐1 increase in IR ↓, (IR ↑ / IR ↓ )ns decreased an average of 0.6% for every hour ending at 0900 to 1800 EST. Differences (DIFR) between measured IR ↑ /IR ↓ and that predicted with the ns regressions for each hour were regressed on a characteristic soil moisture potential (Ψsm) for the dune sand and on a ratio of calculated actual to potential evapotranspiration (ET/ PET) for the Typic Argiaquoll. Correlations of DIFR on Ψsm or ET/ PET were low. Differences in reflectance first appeared to increase with increasing moisture stress, and then decreased with further increase in moisture stress, as leaf rolling reduced the RGPC. These findings suggest one reason for different IR reflectance‐plant moisture stress results reported in the literature, and clearly show that without accurate measures of LAI (or RGPC) and IR ↓ plant moisture stress cannot be detected with measurements of IR ↑

Growth and Foliar Nutrition of White Pine Seedlings as Influenced by Simultaneous Changes in Moisture and Nutrient Supply

AbstractA greenhouse study was used to investigate the effects of varying moisture supply and nutrient solution concentration concurrently on the growth and foliar nutrient concentration of white pine (Pinus strobus L.) seedlings. Seedlings were treated with four nutrient solution concentrations over four different periods of time between irrigations in all possible combinations. Mean seedling weight decreased with reduced nutrient solution concentration and with increasing time between irrigations. The interaction between nutrient solution concentration and irrigation schedule was highly significant in regard to effect on seedling weight.Mean N, K, and P concentrations in the needles showed significant increases with an increase in moisture stress. Irrigation treatment had no significant effect on foliar Ca or Mg concentrations. Of the micronutrients only B and Mn were affected by irrigation treatments. In general foliar concentrations of the macronutrients were negatively correlated with the micro‐nutrients.

Effect of plant population on the production and distribution of dry matter in maize

SUMMARYGrain and total dry weight of maize (Zea mays L.) at final harvest increased by about 50% and 30%, respectively, when the population was increased from 23000 to 48000 plants/ha, but did not increase further with population up to 74000/ha.Between 6 and 10 weeks after sowing, crop growth rate (C) increased by about 40% with increase in leaf‐area index (L) from 2 to 5·5, despite a concomitant increase in moisture stress. Immediately after flowering, which occurred at 10–11 weeks, C increased up to the greatest L attained, 6·7, and would probably have reached a maximum, with L about 7, when nearly all the incident light would be intercepted by foliage. Later, the L at which C was maximal decreased, probably because the photosyhthetic efficiency of leaves decreased faster with time as L increased; 18 weeks after sowing, when L varied between 3 and 5·5, C was maximal when L was 5.The proportion of grain in the dry matter accumulated after flowering increased from 73% when population was 23000/ha to 82% when it was 60000–74000/ha. Stem weight increased until 3–4 weeks after flowering, then remained constant when population was 23000/ha, but decreased in denser populations. The fraction of the ear consisting of grain increased with population.