Physiological Response Of Six Dwarf Ornamental Bamboo Species Under Low Temperature Stress

Extreme whether such as low temperature associated with global climate change always negatively affects the growth of ornamental plant species. To understand responses of six dwarf ornamental bamboo species to low temperature stress, and to screen species with better low temperature stress tolerance for landscape application, two low temperature treatment methods, natural cooling and monitored low temperature were applied to measure changes of ten physiological indexes and one morphological index. These physiological indexes including relative water content in leaves, relative conductivity, proline content, malondialdehyde (MDA) content, soluble protein content, soluble sugar content, superoxide dismutase (SOD) content, catalase (CAT), peroxidase (POD), polyphenol oxidase (PPO). Principle component analysis was carried out to reduce complexity of indexes and select highly related traits. Subordinate function analysis was employed to comprehensively evaluate and rank low temperature stress tolerance of six dwarf ornamental bamboo species. Main conclusions were as follows.1) Analysis of variance and multiple comparisons indicated significant or very significant differences between species and different temperature treatments. All indexes investigated were correlated with each other. The major changes investigated were the increase of protective enzyme activities and the decrease of cell membrane stability. Principle component analysis reduced 10 correlated indexes into several comprehensive indexes with higher contribution. Three major components can be extracted under both natural cooling and monitored low temperature methods:protective enzymes activities and cell membrane stability factor, osmotic regulation factor, protective enzyme activities factor. The results indicated key roles of protective enzymes and osmotic regulation during low temperature stress. With the decrease of temperature, cell wall membrane stability decreased, but the activities of protective enzymes increased.2) Under natural cooling treatment, low temperature stress tolerance of six dwarf ornamental bamboo species can be ranked based on subordinate function analysis of then physiological indexes as:S. chinensis> S. auricoma> A. fortune> A. iadistichus> A. argenteostriata> I. latifolius. Under monitored low temperature treatment, low temperature stress tolerance of six species can be ranked based on subordinate function analysis as: S.chinensis> S. auricoma> A. fortune> A. argenteostriata> A. iadistichus> I. latifolius. According to leaf physiologicalresponses under low temperature stress, six species can be grouped into three levels, which including high tolerance:(S. chinensis, S. auricoma), moderate tolerance (A. fortune, A. iadistichus, A. argenteostriata), low tolerance (I.latifolius).3) According to leaf ornamental index in winter, ornamental value of six dwarf bamboo species can be ranked as:I. latifolius> S. auricoma> S. chinensis> A. iadistichus> A. fortune> A. argenteostriata. All of the six species can maintain good ornamental value in winter in Chengdu, where the average temperature in January is 6.3℃. The six species showed potential in wide application in city garden greening, among which S. auricoma and I. latifolius are the best.