Effects Of Simulated Rainfall Reduction On The Anatomical Structure Of The Stem And Leaf Of Larix Gmelinii

Taking Larix gmelinii in Maoer mountain as the research object, using artificial simulated rainfall reduction field drought experiment, the thesis research the effects of different control degree of rainfall, which is 50% and 100% reduction of rainfall and the restore rainfall the next year on anatomical structure of the stem and leaf, which demonstrates the response of Larix gmelinii to moisture changes and the adaptive mechanism. The specific research results are as follows:(1)Effects of simulated precipitation reduction on the anatomical structure of the stem and leaf of Larix gmeliniiIn simulated precipitation reduction experiment, the effects of precipitation reduction on the different anatomical structure characters of the stem and leaf of Larix gmelinii were not consistent. First of all, the rainfall reduction could inhibit the growth of the stem and leaf of Larix gmelinii, which resulted in the reduction in a number of anatomical structure indexes values of the stem and leaf. The influence embodied on the indexes of the stem xylem structure and leaf anatomical structure, including stem xylem thickness and its proportion in the stem, tracheid annual thickness, tracheid number and tracheid average diameter, total leaf thickness, mesophyll thickness, thickness of vascular bundle, average area of tracheid in the leaf and the thickness of the stratum corneum. Secondly, the experimental results showed that the size of a number of anatomical structures of the stem and leaf decreased in the group of 50% rainfall reduction, but there were a significant increase in the group of 100% rainfall reduction, at the same time, their proportion in the stem and leaf show obvious increase trend along with the rainfall reduction gradient. Most of these structures are parenchymatous tissue, with the function of water conservation and water storage, the water deficit will stimulate the plant’s own defense mechanism, improve its moisture adjustment ability by increasing water conservation and water storage organization.(2)Effects of rainfall recovery on the anatomical structure of stem and leaf of Larix gmeliniiThrough the statistics and comparison to the stem and leaf anatomical structure indexes which regain the rain the next year, it was found that the controlled rain treatment had a persistent effects on the samples, and the anatomical structure indexes of the stem and leaf were affected by the control rain treatment previous year. These indexes are as follows:stem radius, cortical thickness, thickness of phloem, xylem thickness, medullary radius, tracheid growth, quantity and average diameter, total leaf thickness, leaf epidermal thickness, mesophyll thickness, endothelial layer thickness, thickness of transfusion tissue, vascular bundle thickness and average area of tracheid in the leaf. These structure indexes change tendency were similar to those in the control rainfall period. But the stratum corneum thickness between groups was no longer significant after rainfall recovery.(3)Differences in anatomical structure of leaf in long and short branches of Larix gmeliniiThe results showed that the anatomical structure indexes of leaf in the long branches of Larix gmelinii were larger than those of the short branches, including the total leaf thickness, mesophyll thickness near the upper epidermis, mesophyll thickness near the under epidermis, mesophyll thickness, endothelial cell layer thickness, thickness of transfusion tissue, thickness of vascular bundle, average area of tracheid in the leaf and the thickness of the stratum corneum. In contrast, the thickness of the upper and lower epidermis cells of leaf in long branches were smaller than those of the short branches.