Spatial Differentiation Of Heteromorphic Leaves Of Sabina Chinensis And Its Influencing Mechanism

Many plants in nature show the phenomenon of heteromorphic leaf,which is closely related to their habitat in most cases,but there is a lack of sufficient research on how environmental stress affects the occurrence and distribution characteristics of the heteromorphic leaves.In this study,Sabina chinensis seedlings were used as experimental objects to examine the main characteristics Sabina chinensis with different heights and their responses to environmental stress and treatments under conditions of different habitats and stress treatments(pruning,drought,temperature,nutrients,etc.).The results showed as follows:(1)The spatial distribution of the heteromorphic leaves(scaly leaves and thorny leaves)and their response to ecological factors in different stages of growth and development showed a regular pattern.Specifically,the proportion of dry weight of the thorny leaves at lower layer was the highest,followed by the middle,and the upper part(close to zero).For the first branch(here,the stem growing from the root system was regarded as the first level of branch,the branch directly growing from the first level branch was regarded as the second level branch,and so on),the farther from the stem base,the smaller the proportion of thorny leaf number;the farther from the base of the first level of branch,the smaller number of the thorny leaves for secondary branches.The weight ratio of the thorny leaves on the shade side of the canopy was higher than the sunny side.Within a certain range,the weaker the light intensity,the higher the proportion of thorny leaves.Soil nutrient content was negatively correlated with the ratio of thorny leaves.Sometimes the thorny leaves and scaly leaves alternately grew;the thorny leaves often grew from the area of mechanical damage on a compound leaf.Temperature also affected the development of heterotypic leaves.Within a certain range,the lower the temperature,the more abundant the thorny leaves.(2)Artificial pruning significant affected the ratio of heteromorphic leaves.Similar to animal feeding,artificial pruning may promote or exacerbate the expression of certain defense mechanisms in plant.The experimental results showed that after the pruning at the tips of the shoots(together with the stems and leaves),Sabina chinensis tended to grow the longer thorny leaves in an aggregated form in long term;when only the leaves were trimmed,the thorny and scaly leaves often appeared alternately,and the of length of the most thorny leaves is between 0.5-1 cm.(3)The transcriptome results showed that the expression levels of some key genes associated with photosynthetic activity in Sabina chinensis are very low,or even zero,implying that due to stress responses,large thorny leaves might reduce the accumulation of organic matter,and instead allocate more biological materials to the expression of structural proteins and other related to the formation of thorny leaf or stratum corneum related to protective roles.