Research On The Shade Tolerance Of Some Iris Species

By imitating the natural shading condition, five Iris species (Iris germanica, Iris tectorum, Iris japonica, Iris sanquinea, Iris ensata var. chinensis) were researched in the aspects of external morphology, physiological and biochemical characteristics, as well as leaf fluorescence parameters and photosynthesis variation. The results were showed that:With the increasing of shading degree, content of Chla, Chlb and total Chl increase, leaf width and plant height trended to increase while leaf thickness trends to decrease gradually.At different levels of shading treatment, tiller numbers of the five Iris species differed obviously. At the full exposure levels from 100% to 26%, tiller numbers of most of the five Iris species gradually increase. At 8% of full exposure level, tiller numbers of all the species trended to decrease.At all the levels of shading treatment, leaf RPP of Iris germanica, Iris tectorum and Iris japonica varied more slightly than that of Iris ensata var. chinensis and Iris sanquinea.With the increasing of shading time, absolute moisture content of most of the five Iris species trended to increase, and there wasn't obvious difference.With the increasing of shading intensity, net photosynthetic rate (Pn) of the five Iris species declined gradually. The species with small variation ranges were Iris japonica, Iris tectorum and Iris sanquinea.With the increasing of shading intensity, stomatal conductance of the five Iris species declined gradually while intercellular CO2 concentration rises gradually.Variation tendency of transpiration rate (Tr) was similar to that of net photosynthetic rate (Pn), but the former was more gentle. The five Iris species had different declination tendency of transpiration rate, Iris tectorum and Iris germanica had relatively small variation, but Iris japonica had relatively large variation.As there were quite big differences in declination speed of net photosynthetic rate (Pn) and transpiration rate (Tr) in all treatments, there existed obvious differences between the variation tendency of water utilization efficiency(WUE)and the above mentioned indicators. The declination tendency of the five Iris species was not obvious at full exposure 82% and 54% levels, but quite obvious at full exposure 26% and 8% levels.The species in order of light energy utilization efficiency were: Iris japonica, Iris tectorum, Iris germanica, Iris sanquinea, Iris ensata var. chinensis.All the analyses showed that the sequence of the shade tolerance of the five Iris species was Iris japonicaï¹¥Iris tectorumï¹¥Iris germanicaï¹¥Iris sanquineaï¹¥Iris ensata var. chinensis.