Research Of The Growth Characteristics And Stress Resistance Of Clerodendrum Trichotomum Thumb

To support the application of Clerodendrum trichotomum Thumb. in urban landscape construction, the phenological characteristics, landscape feature and growing and developing laws of this tree species were studied in Forestry Test Aboretum of Shandong Agricultural University during 2007 to 2008. Taking one-year-old root-origining plantlets as testing materials, drought stress, waterlog stress and salt stress were treated on Clerodendrum trichotomum Thumb. during late July, 2007 to late August, 2007. By testing the growth and physiology indexes, reaction of Clerodendrum trichotomum Thumb. to different environmental stresses as well as stress-resistance indexes of this tree species were analyzed. The results showed that:Phenological characteristics: Buds began to sprout in late March; leaves were full developed in mid April to late April; branch growth mainly happened in early April to late May; vegetative growth was finished in late June which was also the beginning of reproductive growth; it got into blooming stage from late June to late July; the primary blooming stage was from late July to August; the obvious blooming stage was from early August to early September; fruits began to appear in late August and turned deep blue or purple in early September and the calyxes turned bright red which led to the overlapping phenomenon of blooming period and fruiting period. And all those indicated that Clerodendrum trichotomum Thumb. was an excellent tree species with perfect ornamental characteristics and long ornamental period for landscape construction.Under drought stress:After treated by continuous drought stress for 14 days, the plantlets began to wilt and then about 50% of the plantlets recovered after watering; as drought stress lasting, soil water potential, leaf water potential, relative water content, cell membrane permeability, transpiration rate, net photosynthesis and soluble protein content were all declined while soluble saccharide content and proline content increased, and the activity of SOD and POD increased at first and then decreased. Most of the drought-resistance indexes were significantly correlated to each other while the rest had bad significance which may indicate themselves independent during the treatment of drought stress. The drought-resistance indexes can be divided into four groups by cluster analysis: soil water potential, leaf water potential, relative water content, cell membrane permeability, transpiration rate, proline content and net photosynthesis were divided into Group I; soluble protein content and soluble saccharide content were divided into Group II; POD belonged to Group III while SOD belonged to Group IV. Principal component analysis showed that: soil water potential, SOD, POD were the three most valuable indexes to evaluate drought-resistance property of Clerodendrum trichotomum Thumb. which followed by soluble saccharide content, soluble protein content and net photosynthesis. By comprehensive analysis, the conclusion was that SOD, POD, soluble sugar, soluble protein and net photosynthesis rate can be applied as the main indexes to evaluate the drought-resistance characteristics of Clerodendrum trichotomum Thumb.Under salt stress:While the salt concentration increased and the stress time lasted, branch tips and leaves turned yellow or brown; leaf water potential, relative water content, Chl a/b, Tr and Pn declined while cell membrane permeability, proline content and soluble saccharide content increased, and activity of SOD and POD first increased and then declined. The analysis of variance showed that: under 0.2% and 0.4% salt treatment, the physiological and biochemical indexes did not change significantly while at or more than 0.6% they had significant changes, so under experimental condition the salt level should be less than 0.6% for Clerodendrum trichotomum Thumb. Most of the salt-resistance indexes were significantly correlated to each other while the rest had bad significance which may indicate themselves independent during the treatment of salt stress. The salt-resistance indexes can be divided into three groups by cluster analysis: proline content, net photosynthesis, transpiration rate, Chl a/b, Chl b, cell membrane permeability and relative water content were divided into Group I; soluble saccharide content, Chl a and POD were divided into Group II while SOD belonged to Group III. By comprehensive analysis, theconclusion was that, leaf water potential, transpiration, net photosynthesis rate, porline and relative eletric conductivity can be applied as the main indexes to evaluate the drought-resistance characteristics of Clerodendrum trichotomum Thumb.Under waterlog stress:After treated with excessive water for 8 days, the leaves began to wilt, and the plantlets without any measures to remove excessive water died at the 11th day; leaves of lower branches supplied with excessive water turned yellow or brown; relative water content of leaves, leaf water potential, cell membrane permeability, SOD activity, proline content, soluble saccharide content, net photosynthesis, transpiration rate, chlorophyll and soluble protein content changed significantly under waterlog stress of different levels. As waterlog stress enhanced and stress time lasted, leaf relative water content, leaf water potential, chlorophyll, soluble protein, net photosynthesis and transpiration rate declined while cell membrane permeability, proline content and soluble saccharide content increased, and activity of SOD first increased and then decreased. Most of the waterlog-resistance indexes were significantly correlated to each other while the rest had bad significance which may indicate themselves independent during the treatment of waterlog stress. The waterlog-resistance indexes can be divided into three groups by cluster analysis: proline content, soluble protein content, cell membrane permeability, leaf relative water content, SOD activity, net photosynthesis and transpiration rate were divided into Group I; soluble saccharide content and chlorophyll were divided into Group II while SOD activity belonged to Group III. Principal component analysis showed that: soluble protein, transpiration rate, SOD activity ,chlorophyll and soluble sugar were valuable indexes to evaluate waterlog-resistance property of Clerodendrum trichotomum Thumb.Phenological obervation indicated that Clerodendrum trichotomum Thumb. was a tree species of excellent landscape features with long period; though study on its stress-resistance property. Clerodendrum trichotomum Thumb. was found to be relatively resistant to drought, wet and waterlog stress, and all those properties showed that Clerodendrum trichotomum Thumb. was a good tree species with great potential for exploiting.