A Study On Resistant Physiological Mechanism Of Baldcypress

One year old seedlings of baldcypress (Taxodium distichum) were grown in a pot under greenhouse conditions with varying soil water levels and soil salt (NaCl) (alone and in combination) levels to determine the reactions of growth and physiology. The time of treatment was 130 days, and growth, photosynthetic characteristics, endogenous hormones concentration, enzymes activity, absorption and allocation of nutrients and other physiological indexes were studied during the time of treatment and after treatment. There were three purposes in this study. The first one was to guide baldcypress cultivation in different sites by determining the growth of baldcypress in the conditions of varying soil water levels and soil salt levels. The second one was to reveal the changing tendency of physiological indexes by determining different kinds of physiological indexes under varying soil water levels and soil salt levels. And the last one was to find out the relation between physiological indexes and the growth of baldcypress. The results were as follows: (1) There were significant effects of soil water content and soil salt content on the growth of baldcypress. Maximum growth of baldcypress was observed with flooding and waterlogging conditions, and the growth declined with decreasing soil water content and increasing soil salt content, especially in the drought and higher soil salt content(≥0.3%). (2) There were also significant effects of soil water content and soil salt content on the photosynthetic characteristics, endogenous hormones content, enzymes activity, absorption and allocation of nutrients and other physiological indexes, and the changing tendency of these indexes were also different with varying soil water levels and soil salt levels. (3) Path analysis indicated that the following indexes including NR activity, IAA content, WSD, K/Na in stem, N concentration in the root, stem and leaf had a most remarkable influence on biomass increment, and these indexes of POD and PAL activity, Fe/Na and Mg/Na in leaf, Fe/Na in stem, Ca/Na in root, Mg concentration in stem, Na, Mg and Fe concentration in root also had a significant effect on biomass increment. The second path analysis indicated that NR activity and N concentration in stem were most important indexes influencing biomass increment of baldcypress.