土壤盐分及水分含量对落羽杉光合特性的影响

应用温室盆栽试验方法，采用完全随机试验设计，研究了1年生落羽杉实生苗在不同土壤盐分和水分条件下的光合特性。结果表明，在各种土壤水分条件下，落羽杉净光合速率、气孔导度、叶绿素a和叶绿素b的浓度、叶绿素含量都随着土壤盐分浓度的增加逐渐减少，细胞间隙CO2浓度、叶绿素a与叶绿素b比值逐渐增大，蒸腾速率和呼吸速率因土壤水分的不同随土壤盐分浓度的增加表现出不同的变化趋势；在各种土壤盐分条件下，随着土壤水分含量的降低，落羽杉净七合速率逐渐下降，细胞间隙CO2浓度、叶绿素a浓度和叶绿素含量均在土壤含水量为田间持水量的75％处理下最高，蒸腾速率、气孔导度、呼吸速率、叶绿素b浓度和叶绿素a与叶绿素b比值因土壤盐分的不同随土壤水分含量的降低有不同的变化趋势；在土壤水分供应充足的条件下，落羽杉净光合速率随着土壤盐分浓度的升高而下降主要是非气孔限制所致，而在干旱条件下，落羽杉净光合速率随着土壤盐分浓度的升高而下降则有气孔限制和非气孔限制两种原因，盐胁迫导致叶绿素a浓度的下降也是落羽杉在盐胁迫下净光合速率下降的原因之一。

Effects of Soil Water and Salt Contents on Photosynthetic Characteristics

One year old seedlings of baldcypress(Taxodium distichum L.) were grown in a pot under greenhouse conditions with varying soil water levels and soil salt(NaCl) (alone and in combination) levels to determine photosynthetic characteristics.There were 20 different treatments of soil water and salt contents,and the time of treatment was 100 days.The results were as follows:(1)The net photosynthetic rate,stomatal conductance,chlorophyll a concentration,chlorophyll b concentration,and chlorophyll content decreased with increasing of soil content at varying soil water content,while intercellular CO_2 concentration and chlorophyll a/b increased,but transpiration rate and respiration rate had no unanimous changing tendency;(2)The net photosynthetic rate decreased with decreasing of soil water content at varying soil salt contents,and the water treatment of W_3 among five soil water levels had a highest intercellular CO_2 concentration,chlorophyll a concentration and chlorophyll content,but stomatal conductance,transpiration rate,respiration rate,chlorophyll b concentration and chlorophyll a/b had no unanimous changing tendency;the decreasing of net photosynthetic rate of baldcypress at the soil condition of salt stress and higher water content was caused by non-stomatal limitation,but it was caused at the soil condition of drought by stomatal limitation and non-stomatal limitation;The decreasing of chlorophyll content also was one of the cause of the decreasing of net photosynthetic rate under salt stress.