Recovery of growth in Zinnia elegans after copper stress

The symptoms of copper ion toxicity are well studied, but there is limited information on the mechanisms of plant recovery after stress. The paper deals with the recovery of growth in Zinnia elegans Jacq., treated with 50 and 100 µM Cu2+ for 15 days, then cultivated in normal condition for 30 days. After the recovery period the length of shoot, anatomical changes of root, hypocotyl and stem (first internode) were investigated. It was shown that the copper ions induced a decrease of plant length during stress period. After stress relief for 30 days, the length of hypocotyl and stem of Cu-treated plants increased compared to control. The diameter of root was bigger due to the increase in thickness of cortex and stele. The changes were less noticeable in shoot tissues. The diameter of hypocotyl positively correlates with the thickness of stele. Same effect of copper was observed in stem only in plants, previously treated with 100 µM. The diameter of cortex and metaxylem cells increased in all analyzed organs. No significant differences were found in cell wall thickness of metaxylem cells. The recovery of Z. elegans growth after cooper treatment occurred due to the expansion of cortex and metaxylem cells.