Effects Of Drought And Waterlogging Stress Onthe Growth And Physiology Of Five Shrubs

Water stress is the most common adversity stress in the process of growth and development of plants.The rainfall in South C hina is high,and it is easy to accumulate water after heavy rain.But the seasonal distribution of rainfall is uneven,causing the plants to experience the complex water stress,then affecting their growth.Shrub is an important part of landscape greening,so researching on the adaptability of shrubs to water stress and selecting the plants which are both drought and waterlogging tolerance are of great significance to the construction of Sponge city.Five species of ornamental shrub which are commonly applied in south China were selected for the experimental research,including Allemanda schottii ? Gardenia jasminoides ? Schefflera arboricola‘Variegata' ? Syzygium campanulatum ?andTabernaemontana divaricata.There were four treatments in the research:control,continuous flooding,continuous drought,flooding-drought-rewater.The experiment lasted for 42 days in which we need observe and record morphological changes of plants every 14 days.At the end of the experiment,growth indexs,leaf traits indexs and physiological indexs were measured,and the changes of the indexs under different water treatments were analyzed.The results are as follows:(1)External morphology can be used as an important basis for judging waterlogging tolerance and drought tolerance of plants.The effect of flooding stress on the external morphology of plants was obvious,Allemanda schottii?Gardenia jasminoidesandSyzygium campanulatumperformed well,the root of Schefflera arboricola ‘Variegata' rotted,Tabernaemontana divaricatadropped a lot of leaves,the two plants performed poorly.The effects of drought stress on plant morphology were mainly reflected in the leaf.Syzygium campanulatumand Tabernaemontana divaricataweredamaged seriously,so they were sensitive to drought stress.Allemanda schottii and Syzygium campanulatumrestored obviously under alternate stress of drought and flooding.(2)Flooding stress promoted the root shoot ratio,root length,root surface area and root volume of Allemanda schottii increased(P<0.05),the specific leaf area of all plants were mostly decreased,the leaf dry matter content were significantly increased except Schefflera arboricola‘Variegata'(P<0.05).Under drought stress,the diameter of Tabernaemontana divaricatawas obviously thickened(P<0.05),the diameter of Syzygium campanulatumwas seriously inhibited.The biomass ratio,root shoot ratio of Allemanda schottii andSyzygium campanulatumincreased significantly(P<0.05).There were great differences in the variations of plant height and ground diameter under alternate stress of drought and flooding,and the alternate stress of drought and flooding had no significant effect on root biomass ratio and root shoot ratio of plant.(3)Under flooding stress and drought stress,the net photosynthetic rate and transpiration rate of plants decreased significantly(P<0.05),and the content of MDA increased.Under flooding stress,the chlorophyll content of all plants decreased significantly(P<0.05),the content of soluble protein decreased,The SOD activities of Scheffleraarboricola ‘Variegata'and Tabernaemontana divaricatadecreased significantly(P<0.05).Under drought stress,the SOD activities of plants decreased,and soluble protein content increased.Under alternate stress of drought and flooding,the net photosynthetic rate,stomatal conductance and intercellular carbon dioxide concentration of all plant were basically the same as that of the control.The contents of chlorophyll in other plants were decreased except for Gardenia jasminoides.The SOD activities of Allemanda schottii andGardenia jasminoidessignificantly decreased(P<0.05).The content of MDA in Schefflera arboricola ‘Variegata' andTabernaemontana divaricatasignificantly increased(P<0.05).The content of soluble protein of Allemanda schottii significantly increased(P<0.05),the content of soluble protein of Gardenia jasminoidessignificantly decreased(P<0.05).(4)Through principal component analysis to 19 index under four treatments,the 5 principal components can reflect the information of original data by 84.31 %.Using subordinate functions to evaluate the drought tolerance and waterlogging tolerance of plants,we could know the rank of waterlogging tolerance by five plants from strong to weakis Allemanda schottii,Gardenia jasminoides,Syzygium campanulatum,Tabernaemontana divaricata,Schefflera arboricola‘Variegata'.The rank ofdrought tolerance by five plantsfrom strong to weakis Allemanda schottii,Schefflera arboricola‘Variegata',Gardenia jasminoides,Tabernaemontana divaricata,Syzygium campanulatum.The rank of adaption towater alternation stress by five plants from strong to weak is Allemanda schottii,Gardenia jasminoides,Syzygium campanulatum,Schefflera arboricola‘Variegata',Tabernaemontana divaricata.In general,A llemanda schottii and Gardenia jasminoidesnot only could tolerant waterlogging but also could tolerant drought;Schefflera arboricola‘Variegata' could only tolerant drought;While Syzygium campanulatum could only tolerant waterlogging.Tabernaemontana divaricatacould nottolerant drought and waterlogging.