Cytokinin localization and dynamics in rye plants under chilling and kernel priming with zeatin

Abstract

In the early stages of plant development, a sharp chilling can pose a significant threat to cold-resistant crops, such as winter cereals, in particular, rye. Phytohormones from the cytokinin family play a crucial role in regulating plant response to low-temperature stress. Pre-sowing seed priming with cytokinin solutions is a promising approach to improving the stress tolerance of cereals. The aim of this study was to investigate the impact of chilling on the dynamics and localization of cytokinins in plants of rye cv. Boguslavka in the early stages of development, to determine the possibility of mitigating the adverse effects of cold stress through kernel priming with a zeatin solution, and to assess the effect of this substance on the balance of endogenous cytokinins. Kernels were soaked in either water or a zeatin solution (10—6 М), and plants were grown under controlled conditions of the vegetation chamber. Chilling was induced by exposing 7-day-old plants to the refrigerator for 2 h or twice for 6 h over two days. Endogenous cytokinins were analyzed using the HPLC-MS method. We found significant changes in the cytokinin pool in plants exposed to 2 °C for 2 h while no morphological alterations were observed. The content of trans-zeatin and trans-zeatin riboside increased considerable in the shoots of the plants grown from the kernels soaked in water, whereas in the roots, the level of these cytokinins dropped sharply. Prolonged chilling led to retarded shoot growth and elongated roots. Simultaneously, the level of trans-zeatin, isopentenyladenosine and isopentenyladenine in the shoots decreased to minimum values, while the amount of trans-zeatin riboside increased almost twofold. Transformations of the cytokinin pool in the roots followed a similar pattern. Overall, under the cold stress at the alarm stage, cytokinin balance changes were aimed at maintaining growth processes, while during the acclimation stage, they contributed to growth inhibition. Pre-sowing priming of rye kernels with a zeatin solution allowed plants to maintain normal growth and morphology under of prolonged chilling. This treatment significantly affected the homeostasis of endogenous cytokinins, resulting in a more moderate rearrangement of the cytokinin pool in stressed plants than in the control. We assume that changes in the balance of cytokinins due to seed priming allow plants to improve cold tolerance. Seed treatment with cytokinins could be a promising approach to increasing the adaptive properties of plants.