Research On The Biological Character Of A.sibirica And A.mandshurica

The vegetative organ structure and reproductive organ development of Alnus mandshurica(Callier)Hand.-Mzt.and Alnus sibirica Fisch.Ex Turcz. were observed by using scanning electron microscope.The results will provide basis for studying the phylogeny of Betulaceae and ultilizing A.mandshurica and A.sibirica.The roots of A.mandshurica and A.sibirica have rhizothamnion nodule,the roots of annual plant have began secondary growth,the secondary xylem belongs to diffuse porous wood.A.mandshurica are copsy while A.sibirica are monopodial branching.the buds of A.mandshurica and A.sibirica have pedicle and two perulas;the stem of annual plants closes to apical bud,they have obvious secondary xylem and secondary phloem,the structure of periderm is intact;the stem secondary xylem belongs to diffuse porous and the dermal belongs to closing layer.The morpha of A.mandshurica and A.sibirica leaves are oval and has crenate, there are peltate hair on the distal surface of epiderm,it consists of 2 basal cells,4 stalk cells and 20-25 cephalosome cells,with the acumulation of secretory product,the cells distrupt gradually and disappeared at last;the palisade tissue and spongy tissue of leaves differentiate obviously,belongs to bifacial leaf.Their female inflorescences of A.mandshurica and A.sibirica all appeared multiple aments that consist of multiple spirally arranged cymelets.Each cymelet had 1 primary bract,2 secondary bracts and 2 tertiary bracts.Each floret had a bicarpellate pistil with a dichotomous columnar style.Two pistils of a cymelet were orientated perpendicularly.During the winter,the female inflorescences of Alnus mandshurica were protected by bud scales,while those of Alnus sibirica naked.Their male inflorescences also appeared multiple aments.Cymelets arranged Spirally and each had 1 primary bract,2 secondary bracts and 2 tertiary bracts.The two secondary bracts developed earlier and the two tertiary ones developed later were originated from cymelet primordium.Of the three floret primordia,the middle one was differentiated earlier than the lateral ones.A floret had 4 tepals and 4 stamens,and each stamen had 4 pollen sacs.The tepals were developed earlier than the stamens, both from the floret primordium.During the winter,the male inflorescences of Alnus mandshurica and Alnus sibirica were naked.The pollen grain of A.mandshurica and A.sibirica are polyporous,the nexine become thickening at the pole,while the interval of germinal has the chacter of band-shaped thickening,it has no cover and granular layer in the exine. After pollination,the pollen grain of A.mandshurica and A.sibirica will sprout on style,the supracutaneous cell will form mamillary process,then the pollen tube will cross the mamillary process and entry the style.The fruits of A.mandshurica and A.sibirica belongs to pterocarpous,they are obovate,have two remain style,the weight of 1000 seeds is about 1.4g,the seeds and branches could be used to breed.