Volume 92, Issue 6
December 1983, pages 443-482
pp 443-449 December 1983
Bulbil, the aerial propagating structure of dioscoreas appearing in the axil of leaf or bract, shows diversity in its size and form. The morphology, anatomy and development of bulbil in 11 species ofDioscorea is described. The bulbil resembles the tuberous underground stem in having cork, cork cambium and parenchymatous ground tissue with scattered vascular bundles. The bulbil develops as a composite structure due to diffused growth of more than one accessory bud arising on the abaxial side of the axillary bud.
pp 451-459 December 1983
Anatomy of vegetative parts and its ecological significance in 10 taxa of Indian maritime strand flora, namelyAllmania nodiflora, Canavalia maritima, Euphorbia atoto, Halopyrum mucronatum, Indigofera uniflora, Messerchimidia argentea, Scaevola plumierii, Scaevola taccada, Sesamum prostratum andThespesia populnea are described.
pp 461-465 December 1983
Aqueous leaf extract ofChenopodium ambrosoides prevented infection of tobacco mosaic and sunnhemp rosette viruses when applied to the leaves by increasing the resistance of the host plants. The leaf extract, however, did not inhibit lesion production inC. amaranticolor. The leaf extract induced only localized resistance in many hypersensitive hosts. Lesion production was considerably decreased when the leaf extract was applied to the under surface of leaves and virus challenge inoculated on the upper surface. The inhibitory activity of the leaf extract was reversed by simultaneous application of metabolic inhibitor, Actinomycin-D. The leaf extract was active both at acidic and basic pH.
pp 467-471 December 1983
Developmental anatomy of seeds and fruits inHelichrysum bracteatum andVicoa indica has been investigated. InH. bracteatum the mature seed coat is usually composed of 2 cell layers but inV. indica it is represented by crushed remains of the integumentary cells. Only the outermost layer of the endosperm persists in the mature seeds. The pericarp inH. bracteatum is made up of a layer of epidermis followed by a multilayered sclerenchymatous zone while inV. indica the pericarp shows an epidermis and a few subjacent layers which remain thin-walled and at places include fibrovascular bundles.
pp 473-482 December 1983
Seasonal growth, fruiting behaviour and spore shedding ofHypnea valentiae are described. Populations of this alga were evident all through the year with two half-yearly growth cycles. Tetrasporophytes were abundant throughout the year with two half-yearly peaks. Carposporophytes occurred during the maximum growth periods.