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The aim of this research is to find out the effects of different degrees of drought stress on the growth index and yield of semi-late rice. In this experiment, a pot experiment was conducted with hybrid Tian-you-hua-zhan rice as material. Intermittent irrigation was used as control (CK) at the tillering stage, booting stage, heading stage, and milk stage. Three water stress gradients of light drought (70% saturated moisture content), medium drought (60% saturated moisture content), and severe drought (50% saturated moisture content) were set to monitor the soil moisture content. The plant height, number of tillers, leaf area, and chlorophyll content under different water gradients at different growth stages were measured, and the effects of different water stress treatments at different growth stages on rice growth index, yield, and its components were analyzed. The results showed that the inhibition of the plant height at the jointing and booting stages was the most significant; moreover, the number of tillers and leaf area decreased most significantly at the tillering stage, and the heading and flowering stages had the greatest effect on chlorophyll synthesis. As far as yield is concerned, the most sensitive stages are the heading and flowering stages. Different stress treatments reduced the effective panicle number, 1000-grain weight, and seed setting rate of rice, and reduced the yield by 27.57%, 44.23%, and 46.32% respectively, compared with the normal control. The correlation analysis showed that the correlation degree of affecting yield from large to small was 1000-grain weight, seed setting rate, and effective panicle. Therefore, ensuring water supply at the heading and flowering stage can effectively improve the 1000-grain weight, effective panicle, and seed setting rate, and increase the rice yield and water use efficiency. [ABSTRACT FROM AUTHOR]

In this study, a non-invasive system is proposed for monitoring the health of vine plants by measuring their water stress, with the goal of mitigating frequent extreme meteorological events such as droughts. The envisioned system measures the spatial distribution of the Crop Water Stress Index (CWSI) on the crop field and provides the farmers with precise control over their vine's health and, therefore, on the final quality of their product. To ensure the accurate acquisition of the parameters needed to compute the CWSI, data are collected by field sensors on the ground and by exploiting satellite data. Data fusion then allows us to obtain an associated georeferenced heatmap of the vineyard. The solution has been tested via a prototype, which allowed the collection of information in a vineyard. [ABSTRACT FROM AUTHOR]

To meet the demand for increasing global food production while using limited water resources, crop water stress must be improved in agriculture. Remote-sensing-based plant stress indicators have the benefits of high spatial resolutions, a cheap cost, and short turnaround times. This study discusses the current advancements in agricultural water stress monitoring and irrigation scheduling, some of the challenges that have been met, and the upcoming research needs. Remote sensing systems are prepared to handle the intricate and technical evaluations of agricultural productivity, security, and crop water stress quickly and effectively. We explore the use of remote-sensing systems in the evaluation of crop water stress by looking at the existing research, technologies, and data. This study examines the connection between relative water content (RWC), equivalent water thickness (EWT), and agricultural water stress. Using remote sensing, evapotranspiration, and sun-induced chlorophyll content are examined in connection to crop drought. Spectral indices, remote sensing satellites, and multi-spectral sensing systems, as well as systems that measure land surface temperature, are examined. This critical study focuses on cutting-edge techniques for assessing crop water stress. [ABSTRACT FROM AUTHOR]

In the context of the current climate change, it has become urgently necessary to develop adequate systems to protect horticultural crops. In Romania, the losses caused to these cultures by the extreme weather phenomena, as well as the lack of active intervention measures to combat or limit them, represent the main argument for addressing this field in particular. Vegetable crops are generally sensitive to extreme weather phenomena. In the climatic conditions in our country, the extreme phenomena occur between March and September, which coincides with the vegetation period of the crops. Of these, hail causes significant damage, and in some cases, at high intensity and long-lasting, can cause the calamity of vegetable crops. Another effect can arise in the drought years, when, in the absence of rainfall, the weeds enter into a fierce competition with vegetables, as regards the specific consumption of water and nutrients. The paper presents a review regarding the current methods of vegetable crops protection against the extreme weather phenomena and of weed control in these crops, grown in organic system. Combining the available solutions, adopting integrated strategies for non-chemical weed control can be an important premise for researchers and farmers to protect vegetable crops. [ABSTRACT FROM AUTHOR]

Under drought stress created conditions, growth and development of Amaranthus caudatus L. were investigated considering the rates of photosynthesis and transpiration. Biomass and physiological parameters differed in drought-stressed and control plants. Water use efficiency (WUE) coefficients were calculated for the studied groups of amaranth. In drought conditions WUE is significantly higher than in control. This may indicate the adaptive properties of amaranth to drought stress. [ABSTRACT FROM AUTHOR]

The paper is focused to characterize a limited assortment in the context of a set of drought sensitivity indices, grouping these indices according to the conditions they reflect (stress and / or normal) and the correlations between them. In our research, we aimed also comparing different sensitivity indicators proposed in order to identify the most appropriate index to characterize the behavior of varieties that we have studied in field experiments. The 13 varieties have been tested for 14 years between 2002 and 2015. Based on the calculation formulas for each of the numerous drought sensitivity indices proposed in the literature (stress susceptibility index - SSI; tolerance - TOL; mean productivity - MP; geometric mean productivity - GMP; stress tolerance index - STI; yield index - YI; yield stability index - YSI; harmonic mean - HM; sensitivity drought index - SDI; drought resistance index - DI; relative drought index - RDI; stress susceptibility percentage index - SSPI; modified stress tolerance index - MSTI, as well as the correlations between them in the case of the assortment of varieties experienced at Şimnic under contrasting conditions of water supply, drought sensitivity indices can be grouped in three distinct categories: indices more strongly dependent on stress behavior; indices that reflect the difference in behavior between stress and normal conditions; indices reflecting average behavior. Within each group the indices were very closely correlated, being practically equivalent. Of all the calculated sensitivity indices, the yield index, YI reflects the most direct behavior under stress, relative to the average behavior of all varieties, not influenced by behavior under other conditions, thus being most suitable for characterizing the capacity of indirect methods of describe drought resistance. [ABSTRACT FROM AUTHOR]

The reactive oxygen species are usually generated by normal cellular activities of the aerobic metabolism and play the role of a signal molecule and beneficial growth regulator. When plants are exposed to stress conditions the concentration of reactive oxygen species increases. Therefore, to neutralize these free radicals and to protect cells from oxidative damage enzymatic and non-enzymatic antioxidant systems are activated. In this paper it was investigated the effect of drought on the activities of antioxidant enzymes and on the proline content in leaves of 10 Sallix clones: RO892, RO1077, RO1082, Cozia1, Fragisal, Pesred, Robisal, Inger, Olof and Jorr. The studied plantations were Timburesti area on sandy soil, irrigated and non-irrigated version, comparative to the control plantation Radovan area. The samples were collected in July and there were determined the catalase and peroxidase activity by colorimetric method. The proline content was determined from sulfosalicilc acid extract by colorimetric method with ninhidric acid as reagent using L proline as standard. The obtained results show that the activity of antioxidant enzymes varies with the investigated genotype and with the environmental conditions. In the case of the plants subjected to hydric stress there can be observed an increase in peroxidase activity compared to the irrigated plot. The increase in peroxidase activity suggests a state of oxidative stress, the plants activating a defensive system. The results obtained show an increase in catalase activity and in proline content (with few exceptions) in plants grown on sandy soil in comparison with the control plantation. Measurement of catalase and peroxidase activity and proline content might be used as biomarkers to assess the tolerance of willows for hydric stress. [ABSTRACT FROM AUTHOR]

Plants possess different mechanisms in stress response, where induction of stress-responsive genes provides tolerance to unfavorable conditions. Stress-responsive genes are characterized for functional and regulatory genes that help in overcoming stress by molecular, biochemical and morphological adaptations. NAC transcription factors are one of the regulatory proteins that involved in stress signaling pathway. A putative NAC transcription factor, ONAC016 was identified from drought transcriptomic data. Our data suggested that ONAC106 was induced by drought, but its function in abiotic stress is still unclear. In silico analysis of ONAC106 showed that this gene encodes 334 amino acids, and its protein consists of NAM (No Apical Meristem) domain. The orthologue of ONAC106 was present in several Poaceae family members, suggesting that ONAC106 is unique to monocot plants only. We found that ONAC106 was induced by salt and cold stresses, indicating that this gene involves in abiotic stress response. In addition, we also found that ONAC106 might function in defense response to pathogen invasion. The ABRE (Abscisic Acid Regulatory Element) ciselement was identified in the promoter region of ONAC106, suggesting that it may involve in the abscisic acid (ABA)- dependent signaling pathway. Based on this preliminary result, we hypothesize that ONAC106 may play a role in abiotic stress response by regulating ABA-responsive genes. [ABSTRACT FROM AUTHOR]

As is clear from weather data, the climate of the inner Strandja, Bulgaria, has grown dryer since 1970. As a result, some relic species having low environmental adaptation potential either have been subjected to the risk of mortality from drought, or have migrated upward, to more humid conditions. The aim of our work was to reveal the effect of recent climatic changes on the vascular systems of relic Vaccinium arctostaphylos L., Rhododendron ponticum L. and Ilex colchica Poj. growing in Strandja. These species are recognized to need conservation. The xylem features were studied by Image Analysis set-up using the dated crosssections of the woody samples. Vessel characters were measured ring by ring. Correlations were calculated between the chronologies of the vessel parameters (mean vessel area and vessel density per a growth ring) and daily average temperature and precipitation recorded at Burgas weather station. These correlations were analyzed using a 20-day moving window technique whereby the climatic variables were shifted at 10-day steps from April 1-st to October 30. It was revealed that from 1996 to 2008, V. arctostaphylos mean vessel area, S, (μm²) was rising while the mean vessel density, N/mm², was dropping. The same trends but at considerably lower rates were revealed for R. ponticum in 2001-2008. In I. colchica, the former feature, on the contrary, dropped slightly and the latter rose in 2004-2008. In all three species, relative water conductive area within a growth ring, sw (sum of the vessel areas located in the growth ring /growth ring area), remained constant in R. ponticum, on the contrary, dropped slightly in V. arctostaphylos and rose in I. colchica. Climate signals recorded in vessels showed that April-May air temperatures influenced in xylem of all three species, while June-July temperatures influenced only archaic R. ponticum and V. arctostaphylos. Spring (April) and summer (June 20 - July 10) precipitation had significant positive effect only on these two species but not on I. colchica. The results clearly showed V. arctostaphylos, the most ancient species, were extremely vulnerable to unfavorable climate. When available water diminishes and transpiration rises, increasing vessel area is unfavorable for plant health, because it makes embolism in vascular system highly probable. [ABSTRACT FROM AUTHOR]

Maize (Zea mays L.) is a drought and chilling-sensitive species required well-watered condition and relatively high temperature for optimum growth and higher yield. In cool climate, maize cultivation is done late planting to avoid early spring low temperature and breeding for early-maturing maize hybrids. As to in the hot climate, round up growth of maize is successful by planting drought resisted lines. However, breeding programs is required many crosses and then screening making the studies time and effort consuming. Therefore, the main goal of this study was to evaluate the Turkish hybrid maize lines for different environmental stresses such as drought and chilling during seedling stages in the greenhouse and growth chambers respectively. Thus, fast and least effort screening methodology is suggested to breeding programs crucial for sustainable agro-biotechnology. Initially, fifteen hybrid maize seedlings were exposed to drought and chilling stresses and also grown under control condition for comparative analysis by separately. Then, growth parameters such as leaf length, leaf elongation rate, leaf width, mature cell size, cell production for leaf 3 and leaf 4 and chlorophyll amount after drought treatments was measured at morphological and cellular level. Finally, kinematic analysis was performed and lines are sorted as tolerant and sensitive according to growth retardation and developed stress symptoms degrees. The results showed that each genotypes reveals different stress tolerance degree under separate treatments. Drought stress treatment showed exceed watering is not association with better growing even plants adapted to less watering condition is more tolerant to drought. The results suggest that stress tolerance is controlled by different genetic factors according to growth stages and stress types. Consequently, breeding for several abiotic stresses would be misleading and each trial should be considered separately. Finally, growth chamber screening would be of great advantage for breeding programs prior to field trial by the higher reproducibility and time reduction. [ABSTRACT FROM AUTHOR]

Groundnut is mostly cultivated in the semi-arid area. Here, drought is a major environmental factor which can reduce agricultural productivity. In Southern Oltenia, the cultivation conditions are similar with semi-arid. The aim of this study is the development of drought tolerant groundnut varieties using a classical method such as selection which requires the use of a large and diverse germoplasm. Results of 10 groundnut genotypes are presented in this paper. These were cultivated in 2012 - 2015 period (2013 and 2015 - drought conditions years; 2012 and 2014 - normal years). The objectives of the study were to identify the most adaptable genotypes for the region, the influence of high temperature upon morphological issue of the plants and drought tolerance traits. Pod yield in some genotypes decrease in drought conditions (reduced number of pods and height of plants) as well as in rainy conditions (high number of immature pods and content of water in seed). Other genotypes presented high pod yield in the normal year. From the experimented material it was identified some drought tolerance genotypes and selection method proved to be a reliable criterion of breeding program. [ABSTRACT FROM AUTHOR]

Soil moisture is important circumstance for soil utilization in the agricultural plant production. The great impact on the production is during the drought periods. We prepared the forecast for the soil moisture for the next short period. The decrease trend of volumetric soil water content was observed during the dry season of 30 days with the rainfall up to 3 mm in 2009 and 2010; 8.9.-8.10.2009 (30 days) and 23.6.-22.7.2010 (29 days) in Bocegaj subcatchment, Slovakia. The dynamics vary between the places we observed and the depth. The highest decrease was at the depth of 300 mm, the lowest at the depth of 1000 mm. The differences reached mainly up to 10 percent of volume (average 4.3 % vol.) in 2009 and over 15 percent of volume (average 13.3 % vol.) in 2010. The higher temperature, the soil type, the texture and the different crops influenced the recession of the soil moisture in 2010. The soil dynamics at the farm territory is a primary factor for the crop management and the farm economics. The new measurement devices can help us to evaluate the soil water conditions. [ABSTRACT FROM AUTHOR]

Among the environmental stresses, drought stress is one of the most adverse factors of plant growth and productivity. This study was carried out to evaluate influence of substrate humidity on proline and soluble sugars levels in the leaves of pea. The proline and soluble sugars content did not change very much in control plants during the entire period of investigation, while in drought treated plants, proline content increased dramatically as well as soluble sugars level. Relative water content of leaves was about 64% under control condition, while the drought treatment caused a decrease in RWC to 15%. The correlation-regression analysis of our data revealed a very strong relationship between substrate water content and proline content as well as between peat water content and soluble sugar content in leaves. [ABSTRACT FROM AUTHOR]

Drought stress has a serious effect on plant growth and development in many regions of the world. Green millet (Setaria viridis) is valuable model plants for investigating the C4 grasses for biotic and abiotic stress tolerance. This study was carried out to evaluate influence of substrate water content on photosynthetic pigments and biomass accumulation in green millet. Under mild to moderate drought stress, any decrease of chlorophyll a and carotenoids has been obtained, while severe drought causes significant decreasing in all photosynthetic pigments. Therefore future studies dealing with the strategies to improve the pigments contents under water stress are needed. Drought treatment led to a significant decrease in shoots fresh weight accumulation, while dry weight reduction was obtained under moderate and severe drought. [ABSTRACT FROM AUTHOR]

Climate change is increasing the frequency and severity of drought in the southeastern US with important implications for plant communities including: loss of biodiversity, declines in primary productivity, and shifts in species composition. However, drought impacts may differ depending on existing soil moisture and species physiological tolerances to drought. We characterized the impacts of drought on longleaf pine (Pinus palustris Mill.) plant communities over three decades by re-sampling permanent vegetation plots with increases in drought since 1993. In summer 2019, 10 1000m2 vegetation plots were resampled in South Carolina and Georgia, which represented xeric, intermediate, and mesic sites. In each plot, we identified all plant species, and identified and measured the diameter at breast height of each woody plant. We quantified changes in species richness and composition, tree basal area and density, along with changes in community-level mean traits across time to relation to drought. Sites had increases in cumulative drought severity index and decreases in standardized precipitation evapotranspiration index (mean decrease = -0.18) since the 1990s. Sites with the largest increases in species richness were intermediate or mesic, while the two sites that lost species through time were located in xeric settings. Xeric plots also had decreases in tree density, suggesting these sites are losing young trees. Changes in species richness were positively related to changes in tree density and negatively related to changes in basal area, indicating sites with larger reductions in basal area also had larger increases in species richness. Species composition (as measured by Bray-Curtis dissimilarity) exhibited greater shifts in xeric sites. Community-level leaf nitrogen decreased, while C:N ratios increased in most sites, suggesting a shift toward more drought-tolerant strategies. Collectively our results suggest that xeric longleaf pine plant communities may be more vulnerable to the effects of climate change than intermediate or mesic sites. [ABSTRACT FROM AUTHOR]

Tree-ring reconstructions of past fire activity provide context for forest management and restoration objectives. Our primary objective in this study was to develop a new fire history in the Potomac Highlands of West Virginia where published reconstructions are particularly sparse, but efforts to develop prescribed fire plans are on the rise. We produced a 273-year (1739-2011) fire-scar record from 57 yellow pine (P. pungens, P. rigida, and P. virginiana) trees spread across five topographically diverse sites on Short Mountain in Hampshire County. Fire occurred every 7-15 years on average at individual sites, while a landscape-scale analysis indicates that fire frequency did not change over nearly 160 years (1855-2011). Fires, however, were significantly less extensive during the "exclusion era" (post-1930). No conclusive relationships between drought and fire were identified, although the most extensive fire year (1930) was uniquely dry. These findings complement nearby fire-scar and sediment charcoal records and provide new context for the application of prescribed fire in the Potomac Highlands. [ABSTRACT FROM AUTHOR]