干热河谷番茄苗期叶片光合效率的土壤水分阈值效应

Threshold Effect of Soil Moisture on Photosynthetic Efficiency of Tomato Leaves at the Seedling Stage in Dry-hot Valley, Yunnan, China

本文以番茄植株为供试材料,采用旱棚盆栽人工给水后自然耗水获得系列土壤水分梯度的方法,利用Li-6400光合测定系统测定不同水分条件下番茄光合生理特性。通过光合参数与土壤水分回归分析,结合数学模型求解,研究了番茄苗期叶片光合效率的土壤水分阈值效应。结果表明:番茄叶片净光合速率(Pn)、蒸腾速率(Tr)、水分利用效率(WUE)及光合参数具有明显的水分临界效应。Pn、Tr、WUE和气孔限制值(Ls)均随土壤水分的降低先升高后下降,但是各指标水分临界值表现不同步,其中Tr和Pn的水分饱和点分别为20.68%和18.18%,WUE最高点为15.83%,Ls最高点为10.74%。当土壤含水率低于10.74%,番茄茎和叶片SOD活性均显著提高。土壤含水率10.74%是番茄叶片光合结构损伤的临界点,也是干热河谷番茄苗期生长所允许的土壤水分最大亏缺程度。而土壤含水率15.83%~18.18%为番茄苗期高产高效水含量,此时番茄幼苗叶片具有较高的光合能力和高效生理用水特性,是确保干热河谷番茄高产高效节水管理的关键区间之一。

Tomato plants were selected as the experimental material.Soil water gradients were obtained by the balances between water provision and consumption in experimental pots in a covered shed.The Li-6400 portable photosynthesis system was used to measure the photosynthetic efficiency parameters under different soil water conditions.It was found that the net photosynthetic rate(Pn),transpiration rate(Tr),water use efficiency(WUE)and photosynthetic parameters of tomato leaves had clear thresholds of soil moisture.Pn,Tr,WUE and stomatal limiting value(Ls)first increased and then decreased with decreasing soil water content,but their thresholds were different.The water saturation points of Pn and Tr were 18.18%and 20.68%respectively,the water efficiency point of WUE was 15.83%,and the maximum soil moisture of Ls was 10.74%.SOD activities of tomato roots and leaves increased significantly when soil water moisture was below 10.74%.The soil water of 10.74%was a critical point that the photosynthetic structure of tomato leaves was impaired,and it was also the maximum thershold point of soil water deficit allowed tomato seedling growth in the dry-hot valley.Soil moisture from 15.83%to 18.18%was classified as the intervals of high productivity and high efficiency;in this range,tomato had high photosynthetic capacity and efficient physiological characteristics for water consumption.This range of soil water meets to tomato production with high productivity and high efficiency in the dry-hot valley.