Özet:

Experiments were conducted to evaluate drought tolerance under different levels of water stress in poplar trees. The cuttings of Populus deltoides L. (clone Kranti) were exposed to four different watering regimes (100, 75, 50 and 25% of the field capacity) and changes in physiological parameters related with drought tolerance were recorded. Drought treatments (75%, 50% and 25% FC) decreased net photosynthetic rate (Pn), transpiration rate (E), chlorophyll fluorescence (Fv/Fmax), plant height, number of leaves, specific leaf area (SLA), leaf area index (LAI) and total biomass content in all the three watering regimes compared to control (100% FC). Cuttings were showed poor performance with increasing levels of drought stress. Severity were observed in Pn, E, Fv/Fmax, plant height, stem diameter, leaf area and number of leaves, SLA, LAI and total biomass content with increasing levels of water stress. Decreased CO2 assimilation and transpiration rate due to instantaneous closure of stomata to protect the plants against hazardous effects of water stress leads to overall decrease in biomass of cuttings with 60 days water stress treatments. By visualizing the results, we can say that Scarcity of water is a severe environmental constraint to plant productivity. Drought-induced loss in plant productivity, since both the severity and duration of the stress are critical. Secondly, we can emphasise with our experiment that poplar plants can maintain their better growth and biomass only up to 75-50% of FC after that stress shows its severity so much that the aim of plants is only to survive and biomass maintenance become vague.  

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