Analyses on Drought Resistant Physiological Characteristics of Lippia nodiflora

The drought resistant physiological characteristics of Lippia nodiflora were studied under the continuous high temperature and drought conditions in the summer season in Chongqing by measuring a set of physiological and biochemical indices of the 1 year old sample plant leaves. The sampled plants were divided into two groups, i.e., one group treated by drought stress without watering for different periods of time (no irrigation in 7d, 14d, 21d, 28d, 35d), and one group as control. The results showed that under the drought stress, the leaf water content of L. nodiflora leaves was decreased simultaneously with soil water content. The proline content changed in similar trend with soluble sugar content and the damage rate, all showing the sensibility to the change of drought stress. With the drought intensified, the osmotic adjustment ability was promoted as the accumulation of proline and soluble sugar was increased, indicating the water absorption ability from the soil was enhanced synergically. Under the persistent drought conditions, however, after the drought intensity was beyond the adaptability of the plants, the cell membrane would be damaged seriously, and the related indexes would decline. The determination of malondialdehyde showed that in the environment with high temperature and lasting drought stress, the cell membrane was damaged significantly with gradient variation, and the severe membrane damage could not be reversed by irrigation. The chlorophyll content of the sample leaves showed a specific steady rising trend individually to each of the two groups.