The indicator of cell membrane permeability of wheat seedlings in assessing stress resistance of wheat varieties

The paper presents the results of studies on the use of the permeability index of cell membranes, determined by the relative change in the specific electrical conductivity (EC) of water extracts of tissues of spring wheat seedlings, varieties Novosibirskaya 18, Novosibirskaya 44, Sibirskaya 21 and Omskaya 18, under the combined action of stressors. In model laboratory vegetation experiments, the hourly dynamics of the EC of water extracts of seedling leaves (exposure of leaves to water for 0.5-4.5 h) was investigated under the simultaneous action of chloride salinity (1.3%) and the causative agent of common rot of cereals Bipolaris sorokiniana Shoem. (5000 conidia per grain). It was established that EC increased by 1.5 times and the rate of electrolyte leakage increased twofold in the less resistant variety Novosibirskaya 44 compared to the more resistant Omskaya 18. The daily dynamics of the EC of 10-16-day-old seedlings was studied under the sequential action of seed hyperthermia (43 °C), chloride salinity (1.3%), and Bipolaris sorokiniana Shoem. (5000 conidia per grain). The protective effect of hyperthermia was established in the more resistant variety Sibirskaya 21 (a decrease in EC up to 1.3 times) in comparison with the variant without heating the seeds. In the less resistant variety Novosibirskaya 18, heating the seeds destabilized the state of the cell membranes (increase in EC and electrolyte leakage rate by 1.5 and 1.2 times respectively). The conditions that ensure the identification of the maximum differences in the studied wheat varieties were experimentally determined: the age of seedlings 10 days, the time interval of exposure of the samples to water 1.5-4.5 h. Intervarietal differences in the relative change in the EC values in the variant without heating the seeds were 1.9 times and in the variant with heating the seeds - 3.7 times, with the significance of difference at the levels p ≤ 0.05 and p ≤ 0.01. Intervarietal differences in the relative change in the EC, established for the time interval exposition of electrolytes leakage of 1.5-4.5 h, were 1.50-1.67 times with the significance of difference at the level of p ≤ 0.05. The proposed approach will make it possible to develop a methodology for assessing new genotypes for resistance to the combined action of biotic and abiotic stressors.

Influence of chloride salinity on primary photosynthetic processes in potato leaves

We investigated the effect of 125 mM NaCl on the potato leaves photosynthetic parameters (the content of chlorophylls a, b, and carotenoids; photochemical activity of photosystem II).

Leaf apoplastic alkalisation promotes transcription of the ABA synthesising enzyme Vp14 and stomatal closure in Zea mays L

The chloride component of NaCl-salinity causes the leaf apoplast to transiently alkalinize. This transition in pH reduces stomatal aperture. However, whether this apoplastic pH (pHapo) transient initiates stomatal closure by interacting with other chloride-stress-induced responses or whether the pH transient alone initiates stomatal closure is unknown. To clarify the problem, the transient alkalinization of the leaf apoplast was mimicked in intact maize (Zea mays L.) by infiltrating near-neutral pH buffers into the leaf apoplast. Effects of the pHapo transient could thus be investigated independently from other chloride-stress-derived effects. Microscopy-based ratiometric live pHapo-imaging was used to monitor pHapo in planta. LC-MS/MS and real-time-qRT-PCR leaf analyses showed that the artificially induced pHapo transient led to an increase in the concentrations of the stomata-regulating plant hormone abscisic acid (ABA) and in transcripts of the key ABA-synthesizing gene ZmVp14 in the leaf. Since stomatal aperture and stomatal conductance decreased according to pHapo, we conclude that the pHapo transient alone initiates stomatal closure. Therefore, the functionality does not depend on interactions with other compounds induced by chloride-stress. Overall, our data indicate that the pH of the leaf apoplast links chloride-salinity with the control of stomatal aperture via effects exerted on the transcription of ABA.