土壤水分时间变异对油麦菜水分利用效率的影响机制

刘迪川; 王转; 朱国龙; 龙怀玉; 徐爱国; 张认连

doi:10.11674/zwyf.2021680

土壤水分时间变异对油麦菜水分利用效率的影响机制

Mechanism of soil moisture temporal variance affecting water use efficiency of romaine lettuce (Lactuca sativa L. var. longifolia)

摘要

摘要:
目的土壤水分根据其随时间的变异情况可分为稳定性和波动性土壤水分，稳定的土壤水分有利于提高作物的水分利用效率。我们研究了土壤水分的时间变异影响油麦菜水分、养分吸收利用效率的机制。
方法以油麦菜(Lactuca sativa L. var. longifolia)为供试作物于遮阳网室内进行盆栽试验。设两个供水处理：传统浇灌(traditional irrigation, TI)和负压灌溉(negative pressure irrigation，NPI)，其所提供的土壤水分分别为波动性土壤水分和稳定性土壤水分。供水处理于油麦菜4叶期开始运行，用土壤水分仪测定土壤含水量，每两天测定一次，处理28天后收获。于NPI开始运行的第1、11、21和28 天，测定油麦菜株高、叶片数、最大叶长和最大叶宽，同时用LI-6400便携式光合仪测定油麦菜叶片净光合速率(P_n)、胞间CO₂浓度(C_i)、蒸腾速率(T_r)和气孔导度(G_s)，生化方法分析叶片抗旱生理指标游离脯氨酸(Pro)、丙二醛(MDA)、脱落酸(ABA)、水杨酸(SA)、可溶性蛋白(SP)和可溶性糖(SS)以及稳定碳同位素比值(δ¹³C)和分辨率(Δ¹³C)的变化。
结果 NPI和TI的累计灌水量和平均土壤体积含水量处于基本相同的水平，NPI土壤体积含水量的变异系数为5.0%，属于稳定性土壤水分，TI的变异系数为10.3%，属于波动性土壤水分。NPI处理油麦菜株高、最大叶长和最大叶宽分别显著高于TI 103.8%、155.4%和62.5%。NPI处理4次监测的各项光合参数值大多高于TI，第11 天的T_r和G_s值，以及收获时(处理第28天)的C_i均显著高于TI。收获时NPI处理油麦菜的产量、水分利用效率、叶片含磷量、氮磷钾养分吸收量和Δ¹³C明显高于TI，根冠比、脱落酸含量、可溶性糖含量和δ¹³C明显低于TI。Δ¹³C与水分利用效率呈正相关，与土壤水分变异系数呈显著负相关。
结论相较于传统浇灌提供的波动性土壤水分，负压灌溉提供的稳定土壤水分降低或者避免了土壤水分胁迫，促进了油麦菜地上部的生长发育、光合作用、养分吸收和水分利用效率。

Abstract:
Objective Stable soil moisture is beneficial for improving crop water use efficiency. Here, we investigate the mechanism of how stable soil moisture affect water and nutrient utilization efficiency of romaine lettuce.
Method The pot experiment was conducted in a screen house using romaine lettuce (Lactuca sativa L. var. longifolia) as the experimental crop. Traditional irrigation (TI) and negative pressure irrigation (NPI) were set up to provide fluctuating and stable soil moisture. At the 4-leaf stage of romaine lettuce growth, the treatments were imposed. We used a soil moisture meter to measure the soil moisture content every two days. The crop was harvested 28 days after treatment. The plant height, leaf number, and the most extended leaf length and width were measured on the 1st, 11th, 21st, and 28th day of treatment imposition. The net photosynthetic rate (P_n), intercellular CO₂ concentration (C_i), transpiration rate (T_r), and stomatal conductance (G_s) of romaine lettuce leaves were measured via a Li-6400 portable photosynthesis system simultaneously. The free proline (Pro), malondialdehyde (MDA), abscisic acid (ABA), salicylic acid (SA), soluble protein (SP), soluble sugars (SS), and stable carbon isotope ratios (δ¹³C) and discrimination (Δ¹³C) in romaine lettuce leaves were determined.
Result The cumulative amount of irrigation and mean soil moisture content under NPI and TI were similar. However, the coefficient of variation (CV) of soil moisture content under NPI was 5.0%, indicating the stable soil moisture, and was 10.3% under TI, showing fluctuating soil moisture. Plant height, the most extended leaf length, and leaf width of romaine lettuce in NPI were 103.8%, 155.4%, and 62.5% higher than in TI. The P_n, C_i, T_r, and G_s values in NPI were higher than in TI. Similarly, the T_r and G_s on the 11th day and C_i on the 28th day in NPL were (P<0.05) higher than in TI. The yield, water-use-efficiency, leaf P content, the NPK uptake, and the δ¹³C were (P<0.05) higher in NPI than in TI at harvest, while root/shoot ratio, ABA, SS, and Δ13C were (P<0.05) lower than in TI. Δ¹³C was positively correlated with water-use efficiency and negatively correlated with the CV of soil moisture.
Conclusions Compared with the fluctuating soil moisture in TI, the negative pressure irrigation created stable soil moisture, thus avoiding the possible temporal drought stress for romaine lettuce. This promoted photosynthesis, nutrient uptake, and water-use-efficiency of romaine lettuce and achieved high shoot growth.

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