Volume 80, Issue 1
July 1974, pages 1-50
pp 1-17 July 1974
The paper gives an account of the embryology of a palmatel-leaved palmLivistona chinensis R. Br., a native of China and Japan. It is quite commonly cultivated in India. One speciesL. jenkinsiana Griff. grows wild in Assam Hills.
Various types of embryo sac and embryo development have been reported in different palms, but in the large majority of them it is of the monosporic 8-nucléatePolygonum type, except inHyphaene indica in which it was found to be ofAllium type (Mahabalé and Chenna veeraiah, 1957). The embryo sac in this palm is of the 8-nucleatePolygonum type. This type is found both in the palmate- and pinnate-leaved palms. The embryo development conforms toAsterad type. In early stages of embryogenesis meristem lies in between two growth centres which later develop into cotyledons. One of these, however, is suppressed very early and is over-grown by the other cotyledon. The growing point is terminal and looks to have a single over-grown cotyledon.
The development of embryo upto globular stage is as in other monocotyledons, but its later development is more like that inAgapanthus umbellatus orRanunculus ficaria. The embryogeny thus appears to support the view of suppression of one cotyledon in monocots by the other which overgrows. It would support the contention that both the monocot and dicot embryos might have arisen from some polycotyledonous ancestors.
pp 18-25 July 1974
Embryology ofUtricularia smithiana has been studied and its systematic position as a species separate fromUtricularia caerulea has been justified.
Floral parts arise in acropetalous succession. A transection of an young anther lobe shows a layer of microspore mother cells surrounded by tapetum, a middle layer, an endothecium and an epidermis. Microspore tetrads are decussate and tetrahedral. Tapetum is glandular. Pollen grain is shed at the 3-nucleate stage. Endothecium exhibits fibrillar thickenings.
Embryosac development is of the polygonum type. Placental nutritive tissue is present only at the micropylar region. Embryosac is surrounded by the endothelium only at the central region.
Fertilisation is porogamous and endosperm isab initio cellular. Endosperm haustoria are not very aggressive. Embryogeny conforms to solanad type. Mature embryo is undifferentiated with starch grain filled cells.
pp 26-30 July 1974
Succinic dehydrogenase activity was studied in the liver and kidney ofHeteropneustes fossilis acclimated to 10% (3·2‰) and 30% (9·7‰) seawater. The dilute saline medium stimulates mitochondrial enzyme activity. Significant elevation was observed in the activity of this enzyme in the liver following acclimation, but no significant change occurred in the kidney. The change in the activity probably reflects the metabolic changes caused by the osmotic stress. If so, the data indicate that the effect of salinity stress varies from tissue to tissue.
pp 31-40 July 1974
Six isolates ofPyricularia from cultivated and wild Gramineae and 10 races ofP. oryzae were studied for production of the phytotoxic compound pyriculol in different media under different cultural conditions. Pyriculol production varied with the isolate, the medium and the cultural condition. The results are discussed in relation to the role of toxins in the blast disease of Gramineae.
pp 41-50 July 1974
Three noveltiesFimbristylis amplocarpa (sect.Cymosae),F. multicephala andF. rectifolia (sect.Eufimbristylis) which are recognised during the course of the revision of this genus are described and illustrated.