【摘要】 人工气候箱模拟干旱、强光处理的盆栽试验表明:受旱植株在停水后第3、4天光合速率下降10—15％,量子产量下降13—14％,且有后效应。复水后7天,其功能叶片的量子产量仍比对照低26—35％左右。田间试验表明:水稻齐穗后受旱剑叶的日光合积分值比对照要低10％左右,“午睡”现象更为严重,谷粒减产12.5％,差异达显著值。气孔导度、光合速率与土壤湿度的变化之间有很好的平行关系,可作为植物缺水的诊断指标。一般当气孔导度因受旱而比正常值下降20％以上时,即会引起光合速率较明显的下降,可作为相对诊断量。从绝对量看,一般情况下可以200 μmolm^-2s^-1为临界指标（不包括苗期）。在轻砂质壤土条件下,土壤含水量降至20％左右,即会导致光合速率明显下降,可作为土壤监测的诊断指标。更多还原

【Abstract】 Studies were carried out to examine the influence of drought plus intense light on the photosyn-thetic capacity of rice and to find out the diagnotic indicator for guiding irrigation. LI-6200 portable photosynthetic system was used to measure the net photosynthetic rate(Pn)and stomatal conductance for the plants both in field and in growth chamber . Improved photosynthetic measuring system and ADC 225 infrared gas analyser was used to measure the quantum yield (QY). MC-302 soil moisture and temperature meter was used to monitor the change of soil water content both in field and in pot. The experiment in growth chamber indicated that Pn decreased by 10-50%(Fig. l)and QY decreased by 13-41%(Fig. 2)3 or 4 days after the poted plants were put into the growth chamber and cut off watering. QY of water stressed plants was still 26-35% lower than normal plants 7 days after rewatering (Fig. 3). At the early period of drought, the integral of daily photosynthesis of water stressed plants in field was about 10%lower than that of irrigated plants. The midday depression of photosynthesis is severer for the water stressed plants than normal plants (Fig. 4). Because of drought during filling period. the grain yield of the water stressed plants reduced 12. 5% in comparison with the irrigated plants. As there was a good perallel relationship among Pn ,soil water content and stomatal conductance (Fig. 5,6) ,it was considered that the stomatal conductance can be used as a diagnotic indicator for guiding irrigation. If the value is 20 % lower than that of normal plants or the absolute value is lower than 200 mmol. m~-2s~-1 ,the rice field should be irrigated. So far as the soil water content is considered in our experimental soil conditions (sandy loam) ,the soil should be watered when it reduced from over 25% to about 20%.更多还原