Grafting onto Cucurbita moschata rootstock alleviates salt stress in cucumber plants by delaying photoinhibition

Abstract

To determine how the use of a given rootstock can influence the functioning of the photosynthetic apparatus of the scion under salt stress, the growth, gas exchange, photosystem II (PSII) efficiency, xanthophyll cycle, and chloroplast ultrastructure of nongrafted, self-grafted, and pumpkin-grafted (hereafter referred to as rootstock-grafted) cucumber (Cucumis sativus L.) plants were investigated at day 15 after being treated with 90 mM NaCl. The reductions in plant growth of the rootstock-grafted plants were lower than those of the nongrafted and self-grafted plants under 90 mM NaCl. The net photosynthetic rate, stomatal conductance, maximal and effective quantum yield of PSII photochemistry, photochemical quenching coefficient, and effective quantum-use efficiency of PSII in the light-adapted state of the nongrafted and self-grafted plants were significantly decreased under 90 mM NaCl. However, these reductions were alleviated when the cucumber plants were grafted onto the pumpkin (Cucurbita moschata Duch.) rootstock. The intercellular CO 2 concentrations were significantly increased in the nongrafted and self-grafted plants under 90 mM NaCl, whereas it was decreased in the rootstock-grafted plants. Nonphotochemical quenching (NPQ) and the deepoxidation state of the xanthophyll cycle were significantly increased under 90 mM NaCl, particularly in the rootstockgrafted plants, suggesting the rootstock-grafted plants had higher potential to dissipate excess excitation energy and reduce the probability of photodamage to PSII. Under 90 mM NaCl, the number of grana was reduced, the thylakoids were swollen, and starch granules accumulated in all plants. However, the damage of chloroplast ultrastructure was alleviated in the rootstock-grafted plants. Taken together, the use of C. moschata rootstock alleviated salt stress in cucumber plants by delaying photoinhibition, probably due to a lower incidence of both stomatal and nonstomatal factors limiting photosynthesis.

Effect of Grafting onto Different Rootstocks and some Foliar Applications on Cucumber Production under High Polyethylene Tunnel Conditions.

“…The present results agree with those obtained by Abd-Alla (2002); Liu et al (2012) and Rahmatian et al (2014) who reported that graft compatibility between rootstock and scion is the most important factor influencing the survival of grafted plants. Also, many investigators reported that cucumber plants grafted onto cucurbita ficifolia gave the highest percentage of successful grafted plants .…”

Brassinosteroid alleviates chilling-induced oxidative stress in pepper by enhancing antioxidation systems and maintenance of photosystem II

“…And with regard to increased qP, carboxylation of plant promoted ATP production and improved the rate of consumption in non-cyclic electron transport process. The decrease in F v 0/F m 0 under chilling stress was attributable to the increased excitation energy quenching by PSII antennae and catalytic cycle of cytochrome P450 (Liu et al 2012;Xia et al 2009a;Wu et al 2014). Demmig-Adams et al (1996) reported that absorbed photon energy in plant can be divided into three parts, photon energy absorbed by PSII antennae and trapped by closed PSII reaction centers (E), absorbed photon energy that is thermally dissipated (D) and photon energy absorbed by PSII antennae trapped by open PSII reaction centers (P).…”

Role of arbuscular mycorrhiza in alleviating the effect of cold on the photosynthesis of cucumber seedlings

“…The PN clearly decreased at low temperature but was enhanced by mycorrhiza both at ambient and at low temperature similarly. Decreased CO2 assimilation can be caused by stomatal limitation or by nonstomatal factors (Begcy et al 2012, Liu et al 2012, Shu et al 2014, Zhang et al 2009: CO2 assimilation is primarily limited by gs if accompanied by a decrease in gs and Ci. On the other hand, if gs decreases but Ci does not change or increases, the decrease in CO2 assimilation should be ascribed to nonstomatal factors.…”