GROWTH AND PHOTOSYNTHETIC EFFICIENCY OF Atriplex nummularia UNDER DIFFERENT SOIL MOISTURE AND SALINE TAILINGS

ABSTRACT The disposal of the tailings (wastes) from desalinators is a growing problem, especially in semi-arid regions, and it is necessary to study halophytes such as Atriplex nummularia for the reuse of these saline waters. Thus, the objective of this study was to evaluate the effect of the interaction between levels of soil water content and salinity of irrigation water, gas exchange and growth of Atriplex nummularia Lindl. The plants were cultivated in vases with soils under two moisture levels (50 and 100% of the field capacity) and irrigated with saline waters from dilution of the desalinator waste, to obtain the following electrical conductivities (EC) of 0.39; 1.54; 2.15; 2.79; and 3.63 dS m-1. The experiment was conducted in a greenhouse for 160 days, with a triple factorial arrangement of 2x5x3, in a randomized complete block design with four replications. The photosynthetic, biometric and plant biomass parameters were evaluated. Irrigation with saline water reduced the net photosynthetic rate (A), stomatal conductance (gs), the effective quantum yield of photosystem II (ΔF/Fm’), photochemical quenching (qP) and the electron transport rate (ETR) of the plants for the two conditions of soil moisture. However, it did not impair the efficiencies of water use (WUE) and carboxylation (EIC) of plants. Plant growth rate and leaf biomass were stimulated under irrigation with saline water (EC ≤ 3.63 dS m-1), and when associated with soil moisture of 100% FC leaf biomass gains > 100% were obtained.

摘要
脱盐装置产生的尾矿（废弃物）处置问题日益凸显，尤其在半干旱地区，针对这类盐水的资源化利用，亟需开展诸如银叶滨藜（Atriplex nummularia Lindl.）这类盐生植物（halophytes）的相关研究。为此，本研究旨在探究土壤含水量水平与灌溉水盐度的交互作用对银叶滨藜（Atriplex nummularia Lindl.）气体交换特性及生长状况的影响。

本研究将植株种植于装有土壤的花盆中，设置2个土壤含水量水平（分别为田间持水量（field capacity，FC）的50%和100%），并使用脱盐废弃物稀释配制的盐水进行灌溉，得到电导率（electrical conductivity，EC）依次为0.39、1.54、2.15、2.79及3.63 dS·m⁻¹的灌溉液。

本试验于温室中开展，持续160天，采用2×5×3三因子试验设计，以随机完全区组设计设置4次重复。试验测定了光合参数、形态计量指标及植株生物量相关参数。

在两种土壤含水量条件下，盐水灌溉均会降低植株的净光合速率（net photosynthetic rate，A）、气孔导度（stomatal conductance，gs）、光系统II有效量子产额（effective quantum yield of photosystem II，ΔF/Fm’）、光化学淬灭系数（photochemical quenching，qP）及电子传递速率（electron transport rate，ETR）。但盐水灌溉并未降低植株的水分利用效率（water use efficiency，WUE）与羧化效率（carboxylation efficiency，EIC）。

当灌溉水EC值≤3.63 dS·m⁻¹时，盐水灌溉可促进植株生长速率与叶生物量积累；当土壤含水量维持在100%田间持水量（FC）时，叶生物量增量可超过100%。