Abstract:

This research studied the effects of stress from elevated soil Cu and Pb on seedling growth and physiological characteristics of Galega orientalis. The experiment was a pot trial with plants grown in an artificial soil made up of humus， perlite and vermiculite mixed 4∶1∶1 and treatments included a control （CK） and four concentrations of Cu and Pb stress （240， 360， 480 or 600 mg·kg^–1 applied with irrigation water）. Measurements of seedling shoot and root length and fresh weight were made at 7 and 15 days and physiological indices such as shoot malondialdehyde， proline and soluble sugar and protein levels and peroxidase activity were measured at 21 days. It was found that the shoot length， root length， shoot fresh weight and root fresh weight of G. orientalis showed a pattern of overall increase compared to CK at the lower two Cu and Pb concentrations and shorter stress exposure time， but with increased stressor concentration and exposure duration， root length was decreased by 23.60% compared with CK at the treatment concentration of 600 mg Pb·kg^–1 and 15 days of Pb exposure. Proline and peroxidase levels in G. orientalis exhibited an overall pattern of constant increase with increase in stressor concentration. With increase in Pb concentration， the malondialdehyde content in plants increased with Pb concentration up to an exposure level of 480 mg Pb·kg^–1， but showed a significant decrease at 600 mg Pb·kg^–1， while under stress from Cu exposure the malondialdehyde content showed a pattern of continuing increase with increase in Cu concentration. The soluble sugar content initially increased and then decreased with increasing Pb concentration while at Cu concentrations of 240 and 360 mg Cu·kg^–1， the soluble sugar content of G. orientalis was lower than for CK plants. The soluble protein content was decreased at lower levels of Pb stress， but at the treatment concentration of 600 mg Pb·kg^–1 was increased by 78.35%， compared to CK. Under Cu treatment， the soluble protein content of the plants showed a pattern of decrease with increasing stress concentration and was significantly lower at 600 mg Cu·kg^–1 than at 240 mg Cu·kg^–1. In conclusion， this experiment showed that G. orientalis has a measure of tolerance to Cu and Pb stress， and an ability for uptake of these heavy metals.

Key words: Galega orientalis, copper stress, lead stress, physiological characteristics