ISHS Acta Horticulturae 108: International Cashew Symposium
PRIMARY VASCULARIZATION IN CASHEW (ANACARDIUM OCCIDENTALE L.) |
| Author: | M. SIVADASAN |
| Abstract:
In the mature embryo procambium forms a hollow cylinder in the roothypocotyl axis which is correlated with the tree habit. Prior to germination, protoxylem elements have differentiated not only in the cotyledons and root but also in the hypocotyl and to a certain extent in the epicotyl. The ontogenetic order of maturation of xylem is first in the cotyledons then in root, and later in the hypocotyl and epicotyl. In the root, the differentiation of protoxylem bundles begin in the oldest part and the pattern of longitudinal differentiation is acropetal. In cotyledons also, a similar pattern of differentiation was noted. Unlike in the root and cotyledons, the differentiation of xylem groups of the hypocotyl does not appear to follow a clear-cut direction of differentiation. The xylem strands of the leaf unites with that of the epicotyl further differentiate basipetally down the cotylendonary mode and join the hypocotylary xylem bundles. The continuity of the vasculature between root and hypocotyl, and hypocotyl and cotyledons is by a simple process of ‘bridging-up’. The mode of transition observed in Anacardium occidentale does not correspond with any of the types recorded by Van Tieghem (1891) or Eames and Mac Daniels (1947). | |
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