幼龄胡杨气孔行为对土壤质地和地下水埋深变化的响应

Response of stomatal behavior in Populus euphratica seedlings to alteration in sediment type and groundwater depth

气孔调节是植物适应水分条件变化的关键途径,研究多变生境中植物气孔行为对认识植物的适应具有重要意义。洪水漫溢新形成的河漫滩是胡杨更新的自然生境,其土壤质地和地下水埋深具高度时空异质性。已有研究主要集中于胡杨对地下水埋深变化的生理生态响应,而对土壤质地与地下水变化交互作用影响植物水分关系的认识不足。通过设置土壤质地(砂土(S_(1))、砂壤土(S_(2))、黏壤土(S_(3)))与地下水埋深(W_(1)(30 cm)、W_(2)(60 cm)、W_(3)(90 cm))交互试验模拟幼龄胡杨自然生境,观测分析了不同条件下胡杨气孔导度(G_(s))、气孔导度斜率(g_(1))、光合的气孔限制(L_(s))的变化。研究结果表明:(1)胡杨气孔行为对地下水变化的响应受土壤质地影响;(2)相同地下水埋深时不同土质间G_(s)具显著差异,W_(1)时S_(2)与S_(3)的G_(s)显著高于S_(1);W_(2)时S_(1)与S_(2)明显低于S_(3);W_(3)时S_(3)最大,S_(2)次之,S_(1)最小;(3)相同地下水埋深处理下,g_(1)在S_(1)最大,S_(3)次之,S_(2)最小;(4)相同地下水埋深处理下,W_(1)时S_(2)与S_(3)的L_(s)显著高于S_(1),W_(2)与W_(3)时L_(s)在S_(2)最大,S_(3)次之,S_(1)最小。综上所述,幼龄胡杨气孔行为对地下水埋深变化的响应因土壤质地而异,这可能归因于土壤质地影响根系结构和土壤水的垂直分布,对胡杨早期植物水分关系具有重要影响。

Stomatal regulation is a key way for plants adapting to changes in water condition.Therefore,it is important to understand the response of stomatal behavior in Populus euphratica seedlings to varying sediment type and groundwater depth.The newly formed flood plain is the natural habitat for P.euphratica recruitment,and its sediment type and groundwater depth are highly heterogeneous in time and space.Previous studies have mainly focused on the physiological and ecological response of P.euphratica to the change of groundwater depth.However,the affects of the interaction between sediment type and groundwater depth changes on the plant-water relationship are well understood.This study was carried out at the Akesu National Station of Observation and Research for Oasis Agro-ecosystem.The tested P.euphratica seedlings were two-yearold,transplanted from the flood plain of the upper reaches of the Tarim River in June 2020.P.euphratica seedlings were grown in lysimeters to examine the interactions between soil texture and groundwater depth on stomatal behavior.Each factor included 3 treatments,sandy soil(S_(1)),sandy loam(S_(2)),clay loam(S_(3))for soil texture,and 30 cm(W_(1)),60 cm(W_(2)),90 cm(W_(3))below soil surface for groundwater.Stomatal conductance(G_(S)),stomatal conductance slope(g_(1)),and stomatal limitation to photosynthesis(L_(S))of P.euphratica seedlings under each treatment were obtained during growing season in 2020.The results showed that(1)the response of stomatal behavior in P.euphratica seedlings to alterations in groundwater depth was mediated by sediment type.(2)G_(S) was significantly different between soil textures under the same groundwater depth,with the G_(S) values for S_(2) and S_(3) higher than under W_(1),S_(1) and S_(2) lower than S_(3) under W_(2),and increasing from S_(1) to S_(3) under W_(3).(3)The largest g_(1) occurring at S_(1),followed by S_(2) and S_(1) under the same groundwater depth.(4)The differences in L_(S) between soil texture varied with groundwater condition,with the values in S_(2) and S_(3) significantly higher than S_(1) under W_(1),and under W_(2) and W_(3),the largest occurring in S_(2),followed by S_(3) and S_(1),respectively.In conclusion,the response of stomatal behavior in P.euphratica seedlings to groundwater depth was mediated by soil texture,which can be attributed to the effects of soil texture on the development of root system and the vertical distribution of soil water.Thus,sediment type may be a major factor that affects plant-water relationship in early life history for P.euphratica.