Exogenous methyl jasmonate enhanced kenaf (Hibiscus cannabinus) tolerance against lead (Pb) toxicity by improving antioxidant capacity and osmoregulators

In this study, the effects of exogenous methyl jasmonate (MeJA) on metal uptake and its ability to attenuate metal toxicity in kenaf plants under Pb stress were investigated. The experiment was conducted with five different MeJA concentrations (0, 40, 80, 160, and 320 μM) as a foilar application to kenaf plants exposed to 200 μM Pb stress. The results revealed that pretreatmen of MeJA significantly increased plant dry weight, plant height, and root architecture at all concentrations tested, with the most significant increase at 320 μM. Foliar application of MeJA at 160 μM and 320 μM increased the Pb concentrations in leaves and stems as well as the translocation factor (TF) from root to leaf. However, the bioaccumulation factor in the shoot initially decreased and then increased with increasing MeJA concentration. By increasing enzymatic (SOD, POD, and CAT) and non-enzymatic (AsA and non-protein thiols) antioxidants, MeJA pretreatment decreased lipid peroxidation, O2- and H2O2 accumulation and recovered photosynthetic pigment content under Pb stress. Increased osmolytes (proline, sugar, and starch) and protein content after MeJA pretreatment under Pb stress restore cellular homeostasis and improved kenaf tolerance. Our results suggest that MeJA pretreatment modifies the antioxidant machinery of kenaf and inhibits stress-related processes that cause lipid peroxidation, hence enhancing plant tolerance to Pb stress.

Comparative Analysis of Physiological, Enzymatic, and Transcriptomic Responses Revealed Mechanisms of Salt Tolerance and Recovery in Tritipyrum

Salt stress results in the severe decline of yield and quality in wheat. In the present study, salt-tolerant Tritipyrum ("Y1805") and salt-sensitive wheat "Chinese Spring" ("CS") were selected from 121 wheat germplasms to test their physiological, antioxidant enzyme, and transcriptomic responses and mechanisms against salt stress and recovery. 56 chromosomes were identified in "Y1805" that comprised A, B, and D chromosomes from wheat parent and E chromosomes from Thinopyrum elongatum, adding to salt-tolerant trait. Salt stress had a greater inhibitory effect on roots than on shoots, and "Y1805" demonstrated stronger salt tolerance than "CS." Compared with "CS," the activities of superoxide dismutase and catalase in "Y1805" significantly increased under salt stress. "Y1805" could synthesize more proline and soluble sugars than "CS." Both the net photosynthetic rate and chlorophyll a/b were affected by salt stress, though the level of damage in "Y1805" was significantly less than in "CS." Transcriptome analysis showed that the differences in the transcriptional regulatory networks of "Y1805" were not only in response to salt stress but also in recovery. The functions of many salt-responsive differentially expressed genes were correlated closely with the pathways "peroxisome," "arginine and proline metabolism," "starch and sucrose metabolism," "chlorophyll and porphyrin metabolism," and "photosynthesis."