engleski

Hormonal response of selected Brassica crops under drought stress

Drought stress is one of the most severe abiotic stresses that may affect growth, yields, and product quality of Brassica crops, particularly in Mediterranean, semi-arid and arid environments. Depending of their tolerance, plants have developed different mechanisms to cope with drought at morphological, physiological, cellular and molecular levels. Selected Brassica varieties: Chinese cabbage (B. rapa ssp. pekinensis), white cabbage (B. oleracea var. capitata), and kale (B. oleracea var. acephala) were evaluated to drought with particular focus to the correlations between drought tolerance and phytohormones’ responses (ABA, auxin, brassinosteroids, cytokinins, jasmonates, and SA). Based on the physiological and biochemical stress markers (photosynthetic performance, proline, lipid peroxidation, protein oxidation, and antioxidant enzymes activities) drought tolerance appeared as follow: Chinese cabbage ˂white cabbage˂ kale. As expected, stress hormones (ABA, jasmonates, SA) were found to be strongly correlated with drought tolerance/sensitivity in selected Brassica crops. The most prominent increases in the level of ABA and jasmonates (JA and JA-Ile) were obtained in more sensitive varieties, while SA increased significantly only in more tolerant kale in comparison to corresponding controls. Considering brassinosteroids, a significant increase of typhasterol (TYP) was found in more tolerant kale, while castasterone (CS) and brassinolide (BL) were significantly increased in drought sensitive B. rapa. Increase in the level of indole-3-acetic acid (IAA) was obtained in more tolerant kale in comparison to others. The CK biosynthesis was prominently altered, including CK nucleotides, ribosides and free bases. Free bases cZR and cZ were highly increased in kale in comparison to others. Correlations among phytohormones and biochemical stress markers were discussed based on Pearson’s coefficients and principal component analysis (PCA).

Brassica crops ; drought ; phytohrmones

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