Effect of grafting and gypsum application on cucumber (Cucumis sativus L.) growth under saline water irrigation

Saline water has been increasingly used in agricultural production due to the serious high-quality water deficits in China. However, the use of saline water often leads to negative effects on both soil quality and plant growth. In this study, we investigated the effects of grafting, gypsum (GS) application and their combination on soil properties and plant growth, cucumber yield and fruit quality under irrigation with saline water. The treatments included (i) self-root plants irrigated with nonsaline water (control, C), (ii) self-root plants irrigated with 3 g L-1 saline water (SW), (iii) grafted plants irrigated with 3 g L-1 saline water (SW + G), (iv) self-root plants grown in GS-treated soils irrigated with 3 g L-1 saline water (SW + GS), and (v) grafted plants grown in GS-treated soils irrigated with 3 g L-1 saline water (SW + G + GS). In general, SW treatment significantly increased electrical conductivity (EC), Na+, Mg2+ concentration in soil, Na+ and total Na in plant, and decreased plant K+ concentration, K+/Na+ ratio, chlorophyll b, carotenoid, biomass and fruit yield, when compared to the C treatment. Under saline water irrigation, GS application merely increased soil EC and Ca2+ concentration and decreased soil pH and Mg2+ concentration, but did not affect most plant parameters. In contrast, grafting alleviated the negative effects of saline water on plant growth, by maintaining low Na+ but high K+/Na+ ratio in shoots, and improving most shoot growth related parameters (e.g. chlorophyll a and b, carotenoid, stomatal conductance and transpiration rate), and eventually improved the plant biomass and fruit yield. Interestingly, the combination of grafting and GS application only showed additive enhancements in free proline, starch content and osmiophilic granule number. Our results suggested that grafting had more influence than gypsum application on cucumber growth under saline water irrigation, and was an effective approach in alleviating crop salt stress. (C) 2017 Elsevier B.V. All rights reserved.