Volume 97, Issue 4
August 1987, pages 277-363
pp 277-288 August 1987
The anther is tetrasporangiate. The young microsporangium wall comprises of an epidermis, a fibrous endothecium, a middle layer and a layer of glandular tapetum of binucleate cells. The tapetum is of dual origin and exhibits morphological dimorphism. The development of the female gametophyte conforms to the Polygonum type. An endothelium surrounds the middle part of the embryo sac at maturity. The endosperm isab initio cellular. The chalazal haustorium is single-celled and binucleate. The micropylar haustorium is highly aggressive. To begin with it has two binucleate cells, which subsequently fuse forming a single-celled, quadrinucleate bulbous body. Branched hyphalike tubular processes extending down along the conducting strand of the developing seed reaching almost the chalaza arise from it. The development of the embryo conforms to Crucifer type. The mature seed coat consists of 2–3 layers of cells together with the degenerating remains of the endothelium. The systematic position of the tribe Gerardeae in the subfamily Rhinanthoideae has been evaluated on embryological grounds.
pp 289-294 August 1987
Vesicular-arbuscular mycorrhizal colonisation was assessed on one year old coconut seedlings of 17 cultivars and 4 hybrids, growing in a sandy loam soil. The proportion of root segments with vesicular-arbuscular mycorrhizae ranged from 56·8–95·2%. In general, more root segments of tall cultivars were infected (68·8–95·2%) than those of dwarf cultivars (62·4–75·2) and hybrids (56·8–86·4%). Similar trends were detected in the infection grading and when the spores in soil near to seedlings was examined. The extent of vesicular-arbuscular mycorrhizal colonisation within infected root segments of same cultivars also varied. The vesicular-arbuscular mycorrhizal fungi associated with coconut seedlings includedGigaspora decipens, Gigaspora aurigloba, Gigaspora rosea, Glomus multicaule andGlomus fasciculatum.
pp 295-300 August 1987
Pollination ecology ofSolanum sysimbrifolium was studied. Two species ofXylocopa and one species ofAnthophora are the active pollinators. All the visitors are diurnal and only larger bees are the effective pollinators. It can be concluded that male flowers are advantageous toSolanum and have developed from the close insect-plant dependence.
pp 301-307 August 1987
The main reserve substances viz insoluble polysaccharides and proteins have been localized through progressive developmental stages ofSaxifraga ciliata anthers. The anther wall comprises of the epidermis, the endothecium, the middle layers and the tapetum and serves as a sink for polysaccharides which are mobilised at definite stages of anther development. The epidermal cells and the cells of connective tissue show tannin idioblasts. The effect of mobilization increases considerably in the ageing anther. The accumulation of reserve material in the pollen grain is accompanied by repeated mobilization of starch from the anther wall tissues.
pp 309-314 August 1987
Variations in accumulation of free amino acids and mineral content in the succulent leaves ofSuaeda nudiflora in response to seawater salinity stress (10–40 mS. cm−1) have been studied. Alanine, aspartic acid, glutamic acid, glycine, phenylalanine, proline and serine were found in greater concentration than other amino acids. Under higher salinities, decline in concentration of aspartic acid and glutamic acid and increase in proline were observed. Massive accumulation of Na+ and Cl− was recorded but salinity caused little variations of Ca2+, Mg2+ and SO42−.
pp 315-323 August 1987
Fifty-eight taxa belonging to 3 subfamilies of Acanthaceae have been screened for leaf flavonoids, phenolic acids and aucubins. The patterns of distribution of leaf phenolics among the taxa investigated suggest that: (i) there are 3 well-defined taxonomic groups; (ii) the treatment of Thunbergiaceae as distinct from Acanthaceae (Sensu stricto) is justified; (iii) Nelsonioideae appears to be an intermediate link between Thunbergiaceae and Acanthaceae, and its inclusion within Acanthaceae is justified and (iv) Thunbergiaceae is relatively more primitive than Acanthaceae.
pp 325-332 August 1987
The perennial weeds,Eupatorium adenophorum Spreng. andEupatorium riparium Regel grow abundantly on roadsides, wastelands, ‘jhum fallows’ and other secondary successional communities in the hilly regions of north-east India. Propagation is predominantly by means of wind-borne achenes. Germination of these achenes was studied in relation to temperature, imbibition period and light conditions. At constant temperatures, germination was best at 25°C inEupatorium adenophorum and at 30°C inEupatorium riparium, while alternating temperatures of 15/25°C caused higher germination than the most favourable constant temperatures. The achenes were positively photoblastic and required an imbibition period prior to illumination. Twentyfour hours imbibition was sufficient to sensitize the achenes to light. Red light enhanced germination in both weeds although the effect was more marked inEupatorium adenophorum. The promotory effect of red light was reversed by subsequent exposure to far-red light, while the inhibitory effect of far-red light was removed by a subsequent red light treatment. The result shows a typical phytochrome-mediated germination.
pp 333-335 August 1987
Isolated protoplasts from shoot cultures ofPhysalis minima underwent division, formed colonies and subsequently callus. This system was used for the transformation studies by using T37 strain ofAgrobacterium tumefaciens. Protoplasts were co-cultivated with the bacterium and the resultant callus on analysis showed the presence of nopaline, indicating transfer of the T-DNA.
pp 337-346 August 1987
Venation pattern has been studied in 23 species of the genusCassia Linn. growing in India and these include the species that range in habit from prostrate, erect, shrubs, undershrubs to tall trees upto 10–15 m in height. The venation pattern shows a clear gradation of thickness upto the veinlets of the 6th category and in the size of areoles. Venation pattern and the presence or absence of areoles help to separate one species from the other on the one hand and correlate to the habit of species on the other.
pp 347-358 August 1987
An artificial key for identification of 10 species ofSpermacoce, their diagnostic features and other relevant informations are provided, along with their updated nomenclature.Spermacoce assurgens Ruiz and Pavon is recorded for the first time from the Indian mainland and a new combination,Spermacoce malabarica (Sivar. and Mani.) Sivar.et al is proposed.
pp 359-363 August 1987
Diurone—a common algicide, was used in controlling the oospore formation ofChara species. Ten ppm solution of the chemical was found effective in controlling the sperm production in case ofChara corallina within 72 h of treatment. Fifty ppm solution was toxic toChara zeylanica within 24 h of treatment. The threshold concentration (10–50 ppm) obtained did not affect the germination and vegetative growth of the rice seedlings since the transient effect was quickly reversed within a short time.