Physiological Response And Comparison Of Four Primulina Species Under Shade Tolerance

China is one of the distribution centers of Gesneriaceae,where is rich in species and widely distributed in resources.Primulina is an important genus in Gesneriaceae with high ornamental value and strong ecological adaptability,which has potential to be indoor potted flowers or vertical greening materials.In order to explore its specific tolerance in the condition of low light indoor,4 Primulina species(P.yungfuensis,P.pungentisepala,P.‘Flying Wings',and P.‘Venus')were studied to compare and analyze the shade-tolerance comprehensively,using morphological and physiological-biochemical index determination under different gradient of shade.The main conclusions are as follows:1.After shading treatment,the leaves of 4 Primulina species showed different degrees of changes in leaf shape and color.With the increase of shade degree,the leaf shape of P.pungentisepala and P.P.‘Venus' changed from being elongate to being elliptic,and the leaf color gradually deepened and became lustrous,but all of them did not have etiolation.However,the leaf shape and color of P.‘Flying Wings' and P.yungfuensis did not have obvious differences in the same condition,but in high level shade the leaf of them showed etiolation.2.The leaf tissue structure of 4 Primulina species had significant changes after shade treatment.With the increase of shading ratio,the thickness of leaf of P.yungfuensis,P.‘Flying Wings' and P.‘Venus' rose first and then fell,the thickness of palisade tissue and compactness and thickness ratio of palisade tissue to spongy tissue continued to decrease,and the thickness of spongy tissue continued to rise.The leaf thickness,palisade tissue thickness and spongy tissue thickness continued to increase after P.pungentisepala was shaded,but compactness and thickness ratio of palisade tissue to spongy tissue did not change significantly.3.The physiological characteristics of 4 Primulina species were significantly changed after shade treatment.With the increase of shading rate and the extension of shading time,the content of Pro decreased and the content of Pro and MDA decreased;and POD and CAT activity increased,with SODactivity first increasing and then decreasing.There was no obvious change in the content of ROS,but it was lower than or similar to CK.The content of ABA first rose and then fell.The content of chlorophyll a and chlorophyll b continued to rise,and chlorophyll a/b went down.4.The physiological and biochemical results of different shade treatments showed that the physiological and biochemical tolerance range of P.yungfuensis,P.‘Flying Wings',and P.‘Venus' these three plants is relatively wide,while that of P.pungentisepala is relatively narrow.Among them,in the condition of mild shade,the tolerance time of P.yungfuensis was the longest(60d).However,in the moderate and severe shade conditions,the survival time of P.‘Venus' was the longest(60d).In the tolerance range,the 4 Primulina species generally showed the increase of antioxidant enzyme activity,the decrease of MDA content,the decrease of ROS content and the increase or the invariable change trend of chlorophyll content,which mean it has strong self-regulation ability.5.From the comprehensive evaluation and analysis of the shade tolerance of 4 Primulina species,the order of their shade tolerance from strong to weak was as follows: P.pungentisepala >P.‘Venus' >P.‘Flying Wings' >P.yungfuensis;Through correlation analysis,it was found that POD activity,the content of ABA,palisade tissue thickness,compactness and thickness ratio of palisade tissue to spongy tissue,the content of MDA,chlorophyll a/b and leaf thickness were significantly correlated with shade tolerance.6.An optimum regression equation was established for the evaluation of the shade tolerance of Primulina,and the two most important indexes affecting the shade tolerance of Primulina were POD enzyme activity and the content of chlorophyll a/b,with the influence degree being as high as 94.8%.In this study,the range of tolerance time range and the order of shade tolerance of 4 Primulina species under different shade conditions were determined,and 2 indexes that significantly affected the shade tolerance of 4 Primulina species were selected,which simplified the comprehensive evaluation of the shade tolerance of Primulina,and provided theoretical reference for their cultivation and germplasm selection.