Seedling morphology of Juglans regia L.
2021
Charlotte Georgia Nast
In Juglans regia L., triple fusion precedes fertilization of the egg. An indefinite number of mitoses of the zygote produce a massive embryo with a short, thick suspensor. The apical root meristem and the piloriza are the first regions to differentiate. It is followed by the differentiation of the hypocotyl, then by that of the cotyledons and finally by the development of the epicotile. Cotyledons begin their development by apical, marginal and adaxial meristems, followed by localized intercalary and marginal growth that produces great distortion and folding of the cotyledons. There are 4 traces for each cotyledon. The epicotile is characteristic for having 7 serial shoots in the axilla of each cotyledon. The endosperm is loosely nucleated at first, then becomes cellular. A large vacuoliform structure is found throughout its existence. The seedling has hypogeal cotyledons, with a highly developed primary hypocotyl region and an epicotile with 3-8 pinnate leaves and 7-8 shoots in series in the axil of each cotyledon. The transition phenomenon is limited to the original series of plasmodesmata in the young ephobrion. The bast develops before the wood at the root. The first protoxylem originates from the lower part of the cotyledonous traces.
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