Abstract
Gamma-aminobutyric acid (GABA) is important in plant responses to environmental stresses. We wished to clarify the role of GABA in maintenance of photosynthesis in muskmelon seedlings (Cucumis melo L., cv. Yipintianxia) during saline-alkaline stress. To this end, we assessed the effect of GABA on the structure and function of the photosynthetic apparatus in muskmelon seedlings grown under saline-alkaline stress. These stresses in combination reduced net photosynthetic rate, gas-exchange, and inhibited photosystem II (PSII) electron transport as measured by the JIP-test. They also reduced the activity of chloroplast ATPases and disrupted the internal lamellar system of the thylakoids. Exogenous GABA alleviated the stress-induced reduction of net photosynthesis, the activity of chloroplast ATPases, and overcame some of the damaging effects of stress on the chloroplast structure. Based on interpretation of the JIP-test, we conclude that exogenous GABA alleviated stress-related damage on the acceptor side of PSII. It also restored energy distribution, the reaction center status, and enhanced the ability of PSII to repair reaction centers in stressed seedlings. GABA may play a crucial role in protecting the chloroplast structure and function of PSII against the deleterious effects of salinity-alkalinity stress.
Highlights
Both saline and alkaline soil conditions are deleterious to many plant species
In plants exposed to saline-alkaline stress photosynthetic rate (Pn) declined by 61.6%, Gs declined by 73.4%, and Ls increased 44.9% compared to the control plants (Fig 1)
We observed no significant difference in the transient curves of the control and Gamma-aminobutyric acid (GABA)-treated plants
Summary
Both saline and alkaline soil conditions are deleterious to many plant species. The effects of salinity, an abiotic stress factor of global importance, are well known. Alkaline conditions have been shown to inhibit plant growth, to inhibit photosynthesis, to alter metabolism of reactive oxygen species, and to cause cell death [1,2]. Numerous studies have shown that, when both salt and alkaline stresses are present, these deleterious effects are compounded and are more severe than those that result from salinity alone [3,4,5,6]. In tomato seedlings subjected to this combination of stresses, photochemical quenching parameters were reduced, including.
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