青桐幼苗对水分胁迫的生长及生理响应

青桐观赏效果好，但对其受水分胁迫后的响应机理研究较少，制约了该物种下游产业的发展。为了探究青桐幼苗耐水程度及作用机理，对30%田间持水量（T1）、70%田间持水量（T2）、100%田间持水量（T3）和130%田间持水量（T4）水分胁迫下的青桐幼苗生长指标（株高、茎粗、叶面积）、生物量分配（叶生物量比、茎生物量比、根生物量比）与光合指标（净光合速率、蒸腾速率、胞间CO₂浓度、气孔导度）进行分析。结果表明，随着水分胁迫程度的增加，幼苗的各指标表现为先上升后下降的趋势，当土壤达到T2条件时，幼苗各指标综合表现最佳；T3条件下青桐幼苗净光合速率最高，地上生物量分配较T2条件下高出4%；T2条件下，青桐幼苗叶面积最大，达到196.186 mm²，比叶面积最大，达到512.48，总生物量积累最多，达到17.14 g。当土壤水分达到T2条件时，最适合青桐幼苗生物量积累，可以为幼苗顺利过冬提供充足的储备碳；T4条件下胁迫时间达到10 d，幼苗生长情况出现拐点，胁迫前10 d内幼苗生长较快，但当水分持续性胁迫超过10 d后，幼苗生长趋势减弱，同时萌发出气生根用以响应淹水情况；T1条件下，对青桐幼苗影响极大，最不适合幼苗生长发育。研究结果为青桐幼苗受水分胁迫后的响应机制提供了理论基础。

Growth and photosynthetic characteristics of the seedlings of Firmiana platanifolia under water stress

Firmiana platanifolia is an important tree species for afforestation, but the lack of research on its response mechanism after water stress limits the development of its downstream industry. In order to explore the water tolerance degree and mechanism of Firmiana platanifolia, we analyzed the growth indexes of seedlings (plant height, stem diameter and leaf area), biomass allocation (leaf biomass ratio, stem biomass ratio, root biomass ratio, root biomass ratio and root biomass ratio) and photosynthetic index (net photosynthetic rate, transpiration rate, intercellular CO₂ concentration and stomatal conductance) under 30% field capacity (T1), 70% field capacity (T2), 100% field capacity (T3) and 130% field capacity (T4). The results showed that with the increase of water stress degree, all indexes of the seedlings firstly increased and then decreased, and the seedlings had best performance under T2 condition; the net photosynthetic rate was the highest under T3 condition, and the above-ground biomass allocation was 4% higher than that under T2 condition; under T2 condition, the leaf area and specific leaf area of the seedlings reached the maximum of 196.186 mm² and 512.48, respectively, and the total biomass accumulation reached the maximum of 17.14 g. T2 condition was the most suitable for the biomass accumulation of the seedlings, which could provide sufficient carbon reserve for the seedlings to successfully survive the winter; under T4 condition, the seedlings grew rapidly within 10 days and the growth trend weakened after 10 days, meanwhile, the aerial root emerged in response to flooding; T1 was the most unsuitable condition for the development of Firmiana platanifolia seedling. This study provides a theoretical basis for the responding mechanism of the seedlings under water stress.