Seasonal change of anatomical characteristics of xylem cell in Ulmus parvifolia Jacq
In order to investigate the cell morphology and wall components in the formation of the xylem of Ulmus parvifolia Jacq,with the xylem cell production during a growing season taken as the main line,anatomical and spectroscopic tech-niques were combined to study preliminarily the changes in xylem cell morphology,cell size,and main chemical composi-tion of cell walls.The results showed that 2 rows of earlywood tubular pores appeared in April,dominated by single tubular pores,and a large number of xylem fiber cells began to produce in May,with thick fiber cell wall,until the formation of a-bout 2 mm wide xylem in September;the size of the vessel and the xylem fiber cells were in the elongation stage from April to June,followed by a slight decrease;the diameters of the two types of cells showed a different seasonal pattern of change;the deposition process of cellulose and hemicellulose in vessel cell walls was stable over the seasons;whereas the deposition of cellulose and hemicellulose in wood fiber cells had seasonal differences,with low relative content in the early part of the growing season and a significant increase in relative content in the late part of the growing season,suggesting that there be an asynchrony in the deposition of the major components between the two types of cells.
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