Wheat is a globally important crop used as a main staple food in various countries of the world. The current study was conducted with the objective to evaluate the effect of a high temperature (HT) on osmolytes (starch, sucrose, total soluble sugars, total soluble proteins and proline), physiological parameters (Chl-a, Chl-b, photosynthesis rate, transpiration rate and stomatal conductance), antioxidant enzymes (superoxide dismutase, catalase and peroxidase) and agronomic traits (flag leaf area, spike length, and thousand grain weight) during the grain filling and anthesis stages of wheat cultivars (Fakhr-e-Bhakar, Raj-3765, Jimai-22 and Bayraktar-2000) collected from different regions of the world. Separate experiments for both stages were conducted in a glasshouse and treated with two different temperature regimes, i.e., optimum (OT) (24 °C day; 14 °C night) and high temperature (HT) (32 °C day; 22 °C night) in RCBD for two weeks. The data for osmolytes, antioxidant enzymes and physiological contents were collected at days 3, 5, 7, 9 and 13 after the start of plant stress, while the agronomic traits were collected at maturity. The data obtained were subjected to a statistical analysis using the statistix8.1 and R-program. HT stress significantly reduced all the traits except for the membrane damage, transpiration rate, proline and total soluble sugars, whose values increased considerably in the genotype Bayraktar-2000. However, under both regimes of temperature Fakhr-e-Bhakkar showed a high tolerance against HT stress, as revealed by physiological, biochemical and agronomic evaluations. Moreover, correlation, PCA and heat map analyses indicated that all types of traits are significantly interconnected in determining the crop potential to sustain its growth under HT stress.
Survival of seedlings in arid zone plantation is strongly affected by water stress and drought conditions. Many tree species are able to develop adaptive mechanisms in response to drought stress. The aim of this study was to assess the effect of imposed drought stress on seedlings growth, water use efficiency and survival of three arid zone species (Acacia tortilis subsp raddiana, Salvadora persica and Leptadenia pyrotechnica). Three successive drought cycles were imposed, to a five months old seedlings of the three species. At the end of the drought cycles treatment, water was withheld from both well watered and stressed seedlings and survival was counted until all seedlings wilted out. Growth traits and WUE were measured in drought treated and untreated seedlings.The results showed that imposed drought stress enhanced adaptive traits on these seedlings resulting in better survival. Drought treatment significantly reduced growth traits and WUE in the three species and increased root to shoot ratio and survival. The results pointed out that drought stress conditioning enhanced adaptive traits for these species. However, response was varied among species. S. persica showed better growth than A. tortilis and L. pyrotechnica, alternatively survival was better in A. tortilis and L. pyrotechnica than S. Persica. These results may suggest that in severe drought-prone sites A. tortilis and L. pyrotechnica are preferred.
This study examines intraspecific variability among three sources (KSA, SD5.1 and SD6.2) of Balanites aegyptiaca in Saudi Arabia in their response to different watering frequencies and seasonal changes in vapour pressure deficit (VPD) and air-to-leaf temperature difference (T) under field condition. Irrigation was done once a week, once every two weeks or once every three weeks. Traits measured include: tree height, diameter (DM), relative monthly height (RMHI) and diameter (RMDI) increments, stomatal resistance (Rs), specific leaf weight (SLW). VPD and T were measured during the same time of Rs and SLW measurements. Both Rs and SLW directly responded to irrigation treatment and seasonal variation in T and VPD. Interactive effects of hot weather and water stress increased leaf temperature, resulting in less T and more VPD that induced higher Rs and SLW values. SD5.1 accounted for better responses under water stress, due to its higher Rs and SLW in the same time maintained better growth. DM and RMDI were more responsive to watering stress and varied among the sources. Early seedlings root-toshoot ratio was associated with better growth performance later in the field. The results highlight the role of hot weather and water stress in producing large changes in T and VPD that have a major impact on Rs and SLW. In addition, there is large intraspecific variation in field growth and adaptive responses among seeds brought from different provenances.
This study aimed to investigate the effects of compost addition on leaf area index (LAI), diameter growth and enhancement of seed production and quality in Acacia tortilis established under supplementary drip irrigation. Three composted fertilizer doses (2.5 kg, 5 kg and 7.5 kg/ tree) were compared to NPK (18-18-5 at a rate of 250 gram per tree) and control unfertilized plots. Effects of compost application on leaf area index (LAI), diameter growth, relative monthly diameter increment (RMDI) were monitored during two consecutive years (2014 and 2015). Then the impacts on pods and seeds production, seed weight, seed number per kg, seed quality (NPK and protein), germination per cent and mean germination time (MGT) were determined. Addition of fertilizers produced high effects on LAI. In 2014 NPK resulted in highest LAI values in most measurements, alternatively the status was changed in 2015 where, higher doses of compost produced higher LAI values. LAI results exhibited temporal variability that was associated with the seasonal variation of the year. The results demonstrate higher RMDI and diameter growth under NPK and compost at rate of 7.5 kg/tree treatments. Pods production was higher in plots treated with higher doses of compost. However, seed/husk ratio was higher in NPK plots. There is observed association between fruit and seed production with LAI. NPK and protein contents in seeds, were also, influenced by the presence of organic fertilizers. Cumulative germination and MGT were correlated with seed weight and were higher in plots treated with compost. The results highlight the importance of organic fertilizers under dry land conditions that produced higher LAI and growth which enhanced seed production and quality.
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