Somaye Amraee Tabar; Ahmad Ershadi
Abstract
In this study, the drought tolerance threshold and relationships between some biochemical and physiological responses of two stone fruit rootstocks, Cadaman and GF677, have been investigated. For this purpose, a pot experiment has been carried out in a greenhouse using factorial trial based on a completely ...
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In this study, the drought tolerance threshold and relationships between some biochemical and physiological responses of two stone fruit rootstocks, Cadaman and GF677, have been investigated. For this purpose, a pot experiment has been carried out in a greenhouse using factorial trial based on a completely randomized design with three replications. One-year-old rooted cuttings of two rootstocks are exposed to drought stress (-0.1 (control), -0.6, -1.1, -1.6 MPa) by adding different amounts of polyethylene glycol-6000 to Hoagland nutrient solution. Significant increase in electrolyte leakage and decrease in leaf relative water content of Cadaman and GF677 rootstocks has occurred at -0.6 and -1.1 MPa, respectively. Concentration of photosynthetic pigments and quantum yield of photosystem II (FV/FM) are less affected by drought stress, decreasing significantly in Cadaman and GF677 rootstocks at -1.1 and -1.6 MPa, respectively. Under severe drought stress, photosynthesis, transpiration, intercellular CO2 concentration, and stomatal conductance in Cadaman rootstock decline more considerably, compared to GF677. Moreover, at drought stress of -1.6 MPa, GF677 does not significantly reduce its photosynthesis, despite a substantial decrease in transpiration; however, the relative decrease in photosynthesis of Cadaman at -1.6 MPa has been much greater than the relative decrease in its transpiration and intercellular CO2 concentration, which, in turn, results in a drop in water use efficiency and mesophilic conductance of Cadaman leaves, compared to GF677. It seems that considerable reduction in photosynthesis in Cadaman rootstock, along with stomatal limitations, is largely due to non-stomatal constraints such as loss of cell membrane intact and reduction of chlorophyll, carotenoids and chlorophyll fluorescence. Results show that GF677 rootstock has higher tolerance to severe drought stress, compared to cadaman.
Mohsen Saeidi; Mandana Ajand
Abstract
In this study the effects of source limitation on grain yield of twelve barley cultivars (‘Aras’,‘Jonub’,‘Reihan’,‘Zarjou’,‘Sararoud’,‘Sahra’,‘Fajr30’,‘Karoun’,‘Gorgan’,‘Makouei ’and ...
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In this study the effects of source limitation on grain yield of twelve barley cultivars (‘Aras’,‘Jonub’,‘Reihan’,‘Zarjou’,‘Sararoud’,‘Sahra’,‘Fajr30’,‘Karoun’,‘Gorgan’,‘Makouei ’and ‘Nosrat(’ under post anthesis water deficiency were studied. Source limitation treatments were included that control, removing of awn, leaves below flag leaf, flag leaf and spike photosynthesis. All source limitation treatments significantly reduced grain yield, 1000 grain weight and number of grains per spike. In non-water stress, the highest reduction of grain yield was seen in removing of leaves below flag leaf treatment (27.6%). In water deficiency, the highest and the lowest grain yield reduction were seen in removing of spike photosynthesis (32%) and removing of awn (18.1%). Flag leaf removing significantly increased photosynthesis rate in remaining leaves in non-water stress (28.8%) and water deficiency (10.8%). The evidence from this study suggests that under water deficiency after anthesis, spike photosynthesis is more important than the other current photosynthesis organs in grain yield formation in barley.