Structural Studies On Platanus Acerifolia (Ait.) Willd.

Relationship between cold resistance and structures of Platanus acerifolia(Ait.)Willd.was studied by the method of paraffin method, free-hand section, isolation andmicrotechnique. Through the studies of isolation of one-year roots and stems and threesections of one-year roots of seedlings and of primary vascular tissues of CNZ(cotyledonnode zone), evolutionary evidences of P. acerifolia were discovered.P. acerifolia and cold resistanceVessels and rays of roots and stems: Rays were obvious and wider. Vessels and cellulaalbuminosas were distributed along rays. Longitudinal vessels and lateral rays were bothdeveloped. Rays' cells contained many starch. These all provided advantages for substanceand water transportation, cold resistance and fast-growing of P. acerifolia.There were epidermal hairs, glandular hairs and mamillary process of stems and leaves,which were structural features of water conversation, reflexion and cold resistane.There were cellula albuminosas and starch grains. Epidermal cells of stems were smalland arranged closely. The ratio of palisade tissue to spongy tissue was about 1. So P.acerifolia had certain cold resistance ability and the studies above provided theoretical basisfor study of P. acerifolia cold resistance from the angle of anatomic structures.P. acerifolia and phylogenySecondary xylem of root was diffuse-porous wood. More of the end walls of vessels withlong or short tails were scalariform peforation plate. There were opposite pitting in vessels ofroots and stems, which indicated that P. acerifolia was primitive. There were paratrachealparenchyma around vessels on cross-section of roots and there were abnormal vascularbundles in petioles and leaves. Which indicated P. acerifolia was evolutionary. So P.acerifolia was primitive in evolutionary status but at the same time it also contained someevolutionary characters, which showed its asynchronization in evolutionary progress.There was Long cotyledon node zone in P. acerifolia, which almost occupied the wholehypocotyl and there was exarch diarch actinostele(real diarch and false tetrarch) in root apex.The stele in lower part of CNZ was mesarch diarch haplostele and was primaty. The stele withpith in middle part of CNZ was mesarch and diarch siphonostele. The stele similar with theendarch eustele in stem in upper short part of CNZ only existed in CNZ-stem connectionregion. There was endarch eustele in epicotylary shoot zone. Foliage leaves arising from theembryonic bud was three trace, but the cotyledon of P. acerifolia was two trace. From aboveall we can make the conclusion that CNZ of P. acerifolia seedlings was primitive.