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Titre : Dilution Strategy for Saline Irrigation Based on Physiological Characteristics of Rapeseed (Brassica Napus) and Chinese Violet Cress (Orychophragmus Violaceus) in Salt-Stress and Subsequent Re-Watering Conditions

Auteur : Qaiser Javed；

Grade : Doctoral Dissertation 2017

Université : Jiangsu University

Résumé
Salinity is one of major environmental problem which is limiting the agricultural production. The stress due to salinity is a foremost environmental factor that severely affects the productivity of crop all over the world. Conversely, the output of crop’s production is not increasing to match the requirement of food. Overcoming stress due to water deficiency and salts accumulation is a foremost issue in salt affected areas to ensure agricultural sustainability and continues production of food. Therefore, the content of this dissertation based on the research work which was conducted for Brassica napus L. (B. napus) and Orychophragmus violaceus (O. violaceus). The objective were categorize on the basis of salt-tolerance capacity, photosynthesis, stomatal conductance, transpiration, water-use efficiency, water potential, carbonic anhydrase activity,physiological capacitance and leaf tensity of plants. The objective were ; 1) to investigate the salt induced effects and afterwards re-watering on physiological characteristics of O. violaceus and B.napus,2) to find out best regime for re-watering based on growth and physiological responses of O. violaceus and B. napus under salt stress subsequently re-watering ; 3) to construct a model for prediction of an appropriate regime for dilution of saline water based on electrophysiological characteristics of O. violaceus and B. napus. B. napus and O. violaceus were investigated under growth chamber and greenhouse conditions. The B. napus and O. violaceus were treated in 1st,2nd and 3rd experiments with NaCl, Na2SO4 and mixed treatments as ; NaCl (NC1 : 2.5, NC2 : 5,NC3 : 10) g L-1 ; Na2SO4 (NS1 : 2.5, NS2 : 5, NS3 : 10) g L-1 and mixture of salts (MS1 : 2.5 NaCl +10 Na2SO4 ; MS2 : 10 NaCl + 2.5 Na2S04 ; MS3 : 5 NaCl + 5 Na2S04) g L-1 and 0 as control followed by re-watering NC1^0, NS1^0, NC2^1, NS2^1, NC3^2, NS3^2, MS1^0, MS2^0 and MS3^0,respectively. In the salt stress phase, plant height, stem diameter, leaf area, photosynthesis, water potential, physiological capacitance and leaf tensity decreased significantly with increasingly salts concentration under high salt stress levels of single and mixture of salts as NC3, NS3, MS1,MS2 in B.napus and O. violaceus, respectively. In salt stress phase, maximum reduction in net photosynthetic rate was noted 79.54%,80.72%,84.54%,and 74.84% for NC3,NS3,MS1,MS2,respectively, under high concentration levels in B. napus. While, the reduction in net photosynthetic rate in O. violaceus was found 88.55%, 88.92%, 91.20% and 89.36 under NC3,NS3, MS1, MS2, respectively. Photosynthesis activities under slight (NC1, NS1) to moderate stress (NC2, NS2 and MS3) condition were maintained due to stimulation of carbonic anhydrase activity in both B. napus and O. violaceus. However, during salt-stress subsequently re-watering phase, all physiological parameters were maintained and stable but the recoveries were not found under high stress levels. Better effect of re-watering found in plants due to higher WUER under moderate-stress condition, showed the increment in photosynthetic rate per increment of water content. Relatively as compare to other stress levels more recovery in photosynthetic rate was found after re-watering under medium concentration levels, which were 44.94%, 53.45% and 63.04%, respectively in B. napus. While, the recoveries in photosynthetic rate in O. violaceus were found as 55.62%, 65.46% and 50.82% under moderate concentration levels, respectively.Salt-stress subsequently re-watering enhanced the growth of plants. So, dilution of saline water or re-watering of saline water based on growth and physiological properties should be done at moderate level in both species, which was being considering the best zone for threshold tolerance and production of B. napus and O. violaceus under saline condition.

Mots clés : Brassica napus； carbonic anhydrase activity； dilution model； plant growth traits； leaf tensity； net photosynthetic rate； Orychophragmus violaceus； physiological capacitance； rewatering； salt stress； stomatal conductance； water potential；

Présentation (CNKI)