Dwivedi Padmanabh, Raghavendra A S
Department of Plant Sciences, School of Life Sciences, University of Hyderabad, Hyderabad 500 046, India.
Indian J Exp Biol. 2004 Dec;42(12):1208-11.
Exposure of mesophyll protoplast of pea to osmotic stress decreases the rate of photosynthesis while stimulating marginally the respiratory rate of mesophyll protoplasts. The interaction of osmotic and temperature stress during the modulation of photosynthetic and respiratory rates of pea (Pisum sativum var Azad P1) mesophyll protoplasts was investigated. The protoplasts were exposed to either iso-osmotic (0.4 M) or hyper-osmotic (1.0 M) concentration of sorbitol at 15 degrees and 25 degrees C. The rates of photosynthesis and respiration were studied. At optimum temperature of 25 degrees C, there was a decrease in photosynthesis (< 10%) at hyper-osmoticum (osmotic effect), whereas respiration increased marginally (by about 15%). Low temperature (15 degrees C) aggravated the sensitivity of both respiration and photosynthesis to osmotic stress. At 15 degrees C, the decrease in photosynthesis due to osmotic stress was > 35%, while the respiratory rate was stimulated by 30%. The relative proportion of cytochrome pathway decreased by about 50% at both 15 degrees C and 25 degrees C while that of alternative pathway increased, more so, at 15 degrees C, when the mesophyll protoplasts were subjected to hyper-osmoticum stress. The titration experiments showed that extent of engagement of alternative pathway was higher, the slope value was slightly higher for 15 degrees C compared to 25 degrees C. Low temperature modulates the effect of hyper-osmoticum stress on photosynthesis and respiration, and results in increased participation of alternative pathway.
豌豆叶肉原生质体暴露于渗透胁迫下会降低光合作用速率，同时略微刺激叶肉原生质体的呼吸速率。研究了渗透胁迫和温度胁迫在调节豌豆（Pisum sativum var Azad P1）叶肉原生质体光合和呼吸速率过程中的相互作用。将原生质体在15℃和25℃下分别暴露于等渗（0.4M）或高渗（1.0M）浓度的山梨醇中。研究了光合作用和呼吸作用的速率。在25℃的最适温度下，高渗环境（渗透效应）下光合作用下降（<10%），而呼吸作用略有增加（约15%）。低温（15℃）加剧了呼吸作用和光合作用对渗透胁迫的敏感性。在15℃时，渗透胁迫导致的光合作用下降>35%，而呼吸速率则提高了30%。在15℃和25℃时，细胞色素途径的相对比例均下降了约50%，而交替途径的相对比例增加，在15℃时增加得更多，此时叶肉原生质体受到高渗胁迫。滴定实验表明，交替途径的参与程度更高，15℃时的斜率值比25℃时略高。低温调节了高渗胁迫对光合作用和呼吸作用的影响，并导致交替途径的参与增加。
