Effects of cadmium stress on growth,anatomy and hormone contents in Glycine max (L.) Merr.

Changes in growth parameters, root and leaf anatomy, and stress hormone contents in Cd-stressed soybean (Glycine max L.) seedlings were investigated. Under treatment with 40 µM CdCl₂, the whole plant, root and leaf FW and DW significantly decreased. Also, the whole plant and root length decreased, as well as the chlorophyll and carotenoid contents. This heavy metal affected root and leaf anatomy. In comparison to control, root diameter increased as a consequence of the greater size of the cortex and the vascular cylinder area, and vascular tissues were markedly affected by Cd. In leaflets, the curvature of the mesophyll in internerval areas was observed after Cd treatment. Cd also affected the mesophyll thickness which was reduced by the presence of shorter and narrower cells of the palisade parenchyma. Jasmonic acid content dropped dramatically in Cd-stressed roots, meanwhile ABA and metabolites increased at different times of Cd stress suggesting their involvement in Cd response. ABA peaked at 24 h of Cd stress whereas a strong peak of ABA-GE appeared immediately after the ABA peak. DPA started increasing at 6 h of Cd treatment and the highest peak was recorded at 24 h, as well as the ABA peak. The DPA and ABA-GE contents were higher than the ABA ones Therefore, the alterations induced by the Cd-phytotoxic effect on the growth and anatomy of the soybean seedlings as well as on the ABA and JA root content suggest a possible involvement of these hormones on the sensing and response mediation of these compounds in the organ that first senses the stress.