Comparative Studies of Secondary Phloem of 6 Taxa in Leguminosae

摘要

The comparative studies of the structures of secondary phloem in 5 species and 1 variety of 5 genera of Leguminosae are described. Although the components are common, there are obviously structural changes in secondary phloem among the genera. In Robinia pseudoacacia L., Sophora japonica L., Sophora japonica L., var. pendula Loud,. andCercis chinensis Bunge, the sieve elements are short, cylindrical cells with nearly transverse end walls, simple sieve plates and inconspicuously lateral sieve areas, and in Albizzia julibrissin Durazz and Glediisia sinensis Lam., the sieve elements have oblique and nearly horizontal end walls, compound sieve plates and conspicously lateral sieve areas. The tangential bands of phloem fibres and crystalcontaining cellsalternate with bands of sieve elements, companion cells and phloem parenchyma cells in the secondary phloem in the samples studied, except in G. sinensis and C. chinensis in which no fibres are present in conducting phloem. The 6 taxa share some features--multiseriate rays and homocellular rays, rays with dilatation and curvature in nonconducting phloem and parenchyma cells in tangential bands in transection. The relationship between the characters and systematic taxonomy is also briefly discussed.