Comparative Studies On Anatomic Structures Of Four Species Of Gymnosperm Growing In Different Habitat

Anatomic structures of Pinus sylvestris Linn,Picea koraiensis Nakai,Platycladus orientalis (linn) Franco and Sabina procumbens(Endl.)Iwata et Kusaka growing in Baicheng and Changchun were studied by the methods of paraffin and two-dimensional microtechnique.The study showed that the four gymnosperms evolved structures of drought-and salt-resistance to divergent extents under the saline environment. The cuticles of these four gymnosperms growing in saline environment were significantly thicker than those that growing in mesophytic habitat。The number of stoma was similar between P. sylvestris Linn,P. orientalis (linn) Franco and S.procumbens growing in different habitats, but that of P. koraiensis was different. Most of the stoma of plants growing in saline were closed or were jammed by resin, whereas those of plants growing in mesophytic habitat were open or closed sometimes. There were cryptopores and substomatal chamber in the four gymnosperms growing in two habitats. And substomatal chamber of P. orientalis growing in saline habitat was bigger and there were ventilating tissues formed by two or more substomatal chamber, but there were not or smaller substomatal chamber in P. orientalis growing in mesophytic habitat.The needles of P. sylvestris ,P.koraiensis,P. orientalis and S.procumbens growing in saline habitat were significantly thicker than those growing in mesophytic habitat, probablely because the thicker leaves can decrease water loss in saline and droughty environment which was the result of salt stress.The mesophylls of P. sylvestris growing in two habitats were different. There were smaller and 3-4 layers of mesophylls in P. sylvestris growing in Baicheng, which in favor of photosynthesis. There were larger and two layers of mesophylls in P. sylvestris growing in Changchun which showed weaker photosynthesis. But their methophylls were both cinquefoil-shaped and the cell walls had inner plications which can absorb and secrete materials efficiently. Inner plications increase the ratio of surface area to volume of mesophyll, that is to say, the distribution area of chloroplast.The study also found that the four gymnosperms all evolved ventilating tissues under saline environment. Ventilating tissues can form chamber with low pressure which can strengthen the ability of absorbing oxygen, guarantee the normal respiration and metabolism of plants under saline habitat, decrease the diffusion resistance of photons and so can increase the photosynthetic efficiency and salt resistance.Transfusion tissues of P.sylvestris and P. koraiensis were both developed and belong to...