Volume 96, Issue 2
June 1986, pages 79-158
pp 79-112 June 1986
Current status of the molecular approaches for integrative genetic transformation of plants is reviewed.Agrobacterium-mediated and direct DNA transformation of protoplasts are considered. Elucidation of the molecular events in natural genetic transformation of plant cells in crown gall disease caused byAgrobacterium tumefaciens, has led to the development of T-DNA based vectors for introducing exogenous DNA into plant cells. Various strategies used for this are discussed. So far,Agrobacterium-mediated transformation has been most successful and widely used in dicotyledonous plants. Direct DNA transformation involves either DNA uptake by protoplasts or its mechanical delivery into the cell nucleus. Transformation of both monocotyledonous and dicotyledonous plant cells has been shown by this method. The genes transferred into plants from bacteria, other plant and animal species and various promoters used in chimeric gene constructs for the expression of such genes are listed. Organ specific expression and Mendelian inheritance of transferred genes have been demonstrated. Prospects of the transformation technique for the improvement of crop plants are examined. Gene transfers reported so far indicate that the immediate benefits will be in the development of cultivars carrying herbicide resistance or biocide gene(s). Identification, isolation and cloning of DNA sequences governing resistance to plant diseases or pests, and their introduction into improved cultivars could become possible in the future. Isolation, in vitro modification and re-introduction of the modified gene(s) back into the plant genome is yet another possibility for the future.
pp 113-120 June 1986
Leaf epidermal patterns in 18 species belonging to the genusPennisetum Rich., were described. The variation in the leaf epidermal characters was utilized for the identification of species. Macro hairs were recorded only inPennisetum americanum, Pennisetum clandestinum, Pennisetum polystachyon, Pennisetum pedicellatum, Pennisetum villosum, Pennisetum cenchroides, Pennisetum purpureum × typhoides (hybrid) andPennisetum orientale. Short cells between the veins were paired, solitary or more than two celled. Prickle hairs were absent only inPennisetum polystachyon. Hooks were absent only inPennisetum hohenackeri andPennisetum squammulatum. Stomata with triangular subsidiary cells occur in all the species. Silica bodies are of various types. A dichotomous key was prepared based on epidermal characters for the identification of the different species studied.
pp 121-133 June 1986
A long term study on the phenology of tree species of tropical dry deciduous forest ecosystem of Bandipur, South India has revealed patterns of strong seasonality with respect to leaf and fruit initiation as well as their abscission. The distribution of the duration of the various phenological events was observed to be skewed and there was little interannual variation in events such as flowering and fruiting. This suggests that there are, perhaps, no mast flowering or fruiting species present in the deciduous forests. The phenological changes appear to influence the food, feeding, movement patterns and sociality of the major mammals of this dry deciduous ecosystem.
pp 135-140 June 1986
The extrafloral nectaries ofBignonia illicium occur on the foliage leaves, while the toral nectary is found on the torus around the ovary base. The extrafloral (foliar) nectary is non-vascularised and consists of a single layered secretory tissue followed by a large single celled stalk and single layered foot. The toral nectary is composed of isodiametric parenchymatous cells supplied with phloem. Symbiotic relationship between the animal visitors and the nectaries and their probable functions are discussed.
pp 141-146 June 1986
Anthers are tetrasporangiate. Anther tapetum is of the periplasmodial type and its cells become polyploid. Microspore tetrads are tetrahedral. Pollen grains are shed at 3-celled stage. Ovule is anatropous, unitegmic and tenuinucellate. Embryo sac development is of the Polygonum type. Antipodals are either 2 or 3 in number. They become polyploid and are persistent. Synergids are hooked. Endosperm development is of the cellular type and embryo development conforms to the Grand period I, Megarchetype II, series A and sub series A2 in the first embryonic group and it keys out to the Calendula subtype.
pp 147-152 June 1986
FreshAzolla pinnata (Bangkok) and dry blue-green algae dominated byAulosira sp. andGloeotrichia sp. were inoculated separately at the rates of 500 and 10 kg/ha, 10 and 3 days after transplanting, respectively to evaluate their effects in combination with chemical N fertilizer applied at different stages of rice crop. Split application of 30 kg N/ha urea (15 kg basal and 15 kg 45 days after transplanting) showed higher biomass and N accumulation in bothAzolla and blue-green algae than that of applied whole as basal or 15 kg basal plus 15 kg 20 days after transplantation. Application of 30kg N/ha urea in combination withAzolla basal or dual gave the grain yield as obtained by 3 split application of 60 kg N/ha urea, whereas, use ofAzola basal plus dual showed slightly higher grain yield. Blue-green algae dual culture in combination with 30 kg N/ha urea applied as basal or in two split doses produced significantly low grain yield than that of 60 kg N/ha urea. The application of 30 kg N/ha urea as basal or 50% basal plus 50% 20 or 45 days after transplantation in combination withAzolla or blue-green algae dual culture did not show significant difference in grain yield.
pp 153-158 June 1986
Sporocarps of vesicular-arbuscular mycorrhizal fungi occurring in the rhizosphere and roots ofPennisetum pedicillatum, growing in a red laterite soil were studied. The characteristic features of the sporocarps of each endophyte are described.