Effects of waterlogging stress on the growth and physiological characteristics of male and female <I>Populus cathayana</I> seedlings

Abstract

Aims Although the influences of waterlogging disturbance on the physiology and growth characteristics of plants have been reported for many angiosperms, few studies were carried out in dioecious plants. Our objective was to explore the differences between the sexes of a dioecious species, Populus cathayana, in sex-related growth and physiological responses to waterlogging. Methods One-year-old male and female P. cathayana seedlings were grown in plastic pots in Nanchong, Si- chuan Province, China and were subjected to two water regimes: control (common soil water content) and water- logging (water level 4 cm above soil surface) for 40 days of growth. We investigated sexual differences in malondialdehyde (MDA) content, photosynthetic pigments, gas exchange characteristics, antioxidant enzyme and morphological indices at the end of the experiment. Important findings The waterlogging treatment significantly increased MDA content and number of stems with adventitious roots under water, as well as decreased net photosynthetic rate (Pn), chlorophyll content, super-oxide dismutase (SOD) activity, plant height, basal diameter, total leaf area, specific leaf area (SLA), root biomass, leaf biomass, stem biomass, total biomass and root/shoot ratio (R/S). Moreover, the waterlogging treatment signifi- cantly increased MDA content but decreased SOD activity, Pn, carotenoids (Caro) content, chlorophyll a/b ratio, SLA, root biomass and R/S in female plants, and males had higher stomatal conductance (Gs), intercellular CO2 concentration (Ci), transpiration rate (Tr), more adventitious roots and greater plant height than females. The re- sults indicated that morphological growth and physiological progress of the P. cathayana seedlings were seriously inhibited by the waterlogging treatment. Males may possess greater waterlogging resistance than females with higher photosynthetic capacity and number of adventitious roots maintaining plant growth under waterlogging stress.