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14 C Translocation pathways in honeylocust and green ash: Woody plants with complex leaf forms
Author(s) -
Larson Philip R.,
Dickson Richard E.
Publication year - 1986
Publication title -
physiologia plantarum
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.351
H-Index - 146
eISSN - 1399-3054
pISSN - 0031-9317
DOI - 10.1111/j.1399-3054.1986.tb01226.x
Subject(s) - petiole (insect anatomy) , biology , phyllotaxis , botany , apex (geometry) , chromosomal translocation , fraxinus , aerial root , meristem , genus , ecology , biochemistry , shoot , gene , mangrove
Long‐distance transport in plants requires precise knowledge of vascular pathways, and these pathways differ among species. This study examines the 14 C translocation pathways in honeylocust ( Gleditsia triacanthos L.) and green ash ( Fraxinus pennsylvanica Marsh.), species with compound leaves, and compares them with those of cottonwood ( Populus deltoides Bartr. ex Marsh.), a species with simple leaves. The stem vasculature of honeylocust conforms to a 2/5 helical phyllotaxy and that of green ash to a decussate phyllotaxy. The plastochron is relatively long in both species – 2.5+ days in honeylocust and 4.5+ days in green ash. Consequently, the transition from upward to downward translocation from mature source leaves is abrupt and occurs close to the apex. Export of 14 C from localized treatment positions within a leaf was found to vary both quantitatively and spatially. To determine export patterns, 14 CO 2 was administered to either individual leaflets of once‐pinnate or pinnae of bipinnate leaves of honeylocust, and to either individual veins of simple or leaflets of compound leaves of green ash. Transections of either the petiole or rachis base were then examined for 14 C by micro‐autoradiography. In all cases, as treatment positions advanced acropetally in the leaves, the bundles translocating 14 C were situated more dorsally in the basal petiole and rachis vasculatures. 14 C was confined to the right side of the vasculature when structures on the right side of a leaf were treated. Compound leaves of both species mature acropetally. Thus, mature basal pinnae of honeylocust and basal leaflets of green ash translocate acropetally to younger leaf parts that are still rapidly expanding. All translocation pathways, both in the stem and leaf, conformed with vascular organization previously determined by anatomical analyses.