Comparison Of Physiological Response And Negative Tolerance Of Three Species Of Tradescantia To Low Light Stress

In order to explore the tolerance and adaptation mechanism of three species of Tradescantia plants to low light environment,Tradescantia cerinthoides Tradescantia flurnuensis cv.’Variegata’ and Tradescantia fiuminensis were selected as experimental materials,and five photosynthetically active radiation gradients L0(100μmol·m-2·s-1)、L1(40μmol·m-2·s-1)、L2(20μmol·m-2·s-1)、L3(10μmol·m-2·s-1)、L4(2μmol·m-2·s-1)were set in artificial climate box.The morphological changes,photosynthetic characteristics and physiological indexes of the three plants under low light environment were measured,and the shade tolerance was compared by principal component analysis and membership function analysis.The test shows that:(1)After 50 days of low light treatment,the leaf shape and color of the three species of Tradescantia showed different changes.With the weakening of photosynthetically active radiation,the leaves of Tradescantia cerinthoides ’Nanouk’ and Tradescantia fiuminensis become larger and thinner,and the leaf color is deeper and brighter.The leaf size of Tradescantia flurnuensis cv.’Variegata’ has no obvious change,but a large number of new leaves with small leaves grow.Under the lowest photosynthetically active radiatio(L4),the three species of Tradescantia all appeared leaf yellowing,leaf edge overturning and plant lodging.The Tradescantia cerinthoides’Nanouk’ Under the lowest photosynthetically active radiatio(L4)died on the 45th day of stress,and the flower leaf Tradescantia flurnuensis cv.’Variegata’ and Tradescantia fiuminensis did not die in the whole test process under all gradients.(2)The physiological characteristics of the three plants changed significantly after 50 days of low light stress..Under the light intensity of L0 and L1,the SOD activity of the three plants first increased and then decreased or continued to decrease,the soluble protein content increased,the MDA content decreased,the electrical conductivity decreased,the chlorophyll a and b content increased,the A/B ratio decreased,the Fv/Fm,qP and ETR increased,the Fo decreased,and the relative water content of the leaves did not change much.Under L2 light intensity,except that the indexes of Tradescantia cerinthoides’Nanouk’ deteriorated significantly in the later stage of stress,the growth of Tradescantia flurnuensis cv.’Variegata’ and Tradescantia fiuminensis was not greatly affected.Under L3～L4 light intensity,the SOD activity of the three plants continued to rise or first increased and then decreased.The changes of MDA content,electrical conductivity,leaf relative water content and various fluorescence parameters were opposite to those in L0 and L1 treatment groups.The chlorophyll content increased significantly and the chlorophyll a/b value decreased.(3)The comprehensive evaluation results of negative tolerance showed that the order of negative tolerance from strong to weak was:Tradescantia fiuminensis>Tradescantia flurnuensis cv.’Variegata’>Tradescantia cerinthoides’Nanouk’;The single indexes with strong correlation with shade tolerance were SOD activity,soluble protein content,chlorophyll a+b content,chlorophyll a content,chlorophyll b content,chlorophyll a/b,qP and ETR.(4)Through principal component analysis and membership function analysis,eight indexes that significantly affect the shade tolerance of three species of Tradescantia were selected,which simplified the comprehensive evaluation of shade tolerance of Tradescantia,and provided a theoretical basis for its cultivation,maintenance and garden application.