Volume 100, Issue 6
December 1990, pages 361-443
pp 361-368 December 1990
The streams selected for the study pass through deforested catchments, and even their riparian zones are devoid of trees. Due to low level of nutrients, the streams support reduced algal flora (14 genera; 35 species) and low epilithic algal biomass (0·07–1·14 mg chlorophylla m−2). Persistence of high N∶P atomic ratio at all sites suggests phosphorus limiting condition. Algal assay was used to determine the effects of nitrogen, phosphorus and trace element supplementation on algal growth potential of stream water. Addition of phosphorus significantly increased the cell yield of test alga,Selenastrum capricornutum, thereby confirming phosphorus limitation of algal growth in the selected streams.
pp 369-373 December 1990
The entry ofPeronospora parasitica conidia through stigma, ovary wall and its establishment in the ovary is clearly demonstrated. The pathogen also enters directly through the inflorescence axis of the mother plant. The infection through stigma and ovary wall results in embryonal infection. The infected seeds transmit the downy mildew disease and a direct correlation is noticed between embryo infection and seed transmission of the pathogen.
pp 375-378 December 1990
A field study of rhizoplane microfungi associated with little bluestem (Schizachyrium scoparium (Michx.) Nash), a common tallgrass prairie species, had indicated thatPenicillium chrysogenum Thom andTrichoderma harzianum Rifai outcompeted each other in unfumigated and fumigated soils, respectively. To investigate the mechanisms of competition, interactions between the two fungi were studied in laboratory experiments using an artificial model system. Mutual suppression did occur. The first-inoculated fungus was less affected. Some detrimental residual effects on the growth of one species were observed when it was grown along with the killed mass of the other in the same medium.
pp 379-382 December 1990
Microfungi were isolated from earthworm (Drawida assamensis) gut contents and freshly laid worm casts of a pineapple plantation field using Warcup’s soil plate method. A total of 17 species of microfungi were isolated, out of which 16 occurred in the anterior region, 12 in the middle region and 10 in the posterior region of the gut and 10 in the worm cast respectively. One species was restricted to posterior region of the gut and the worm cast. The digestion of microfungi in earthworm’s digestive tract occurred in a trend anterior>middle>posterior.
pp 383-392 December 1990
Gracilaria edulis (Gmel.) Silva is represented by different morphological forms in the Mandapam region. The morphological variation of selected characters has been analyzed and quantified. Characters included basal branch constriction, branch endings, branch attenuation, stoutness of the thallus, angle of divergence of branches, branching index, sizes of medullary, subcortical and cortical cells, and gradation of cell size from cortex to medulla. All the characters showed continuous variation; however, branching index and branch attenuation showed significant negative correlation between them.
pp 393-398 December 1990
Plantago lagopus L., a weed belonging to family Plantaginaceae, has several features that allow its pollen to be easily drifted by wind. The syndrome of anemophily sensu Faegri and van der Pijl is represented in this species. In addition, some individuals in all populations are male sterile, and all plants contain dimorphic pollen within their pollen sacs. Pollen dimorphy ensures the dual requirement of dispersal over long distances and easy trapping by the plumose stigma.
pp 399-407 December 1990
Vascular supply to leaf in 8 species of the fern genusPteris is described. Except inPteris cretica in which the stipe is supplied by a pair of ribbon like vascular bundles, stipe vasculature of the other 7 species studied is solitary and gutter-shaped; in transection the vascular bundle inPteris cretica, Pteris dactylina andPteris stenophylla is V-shaped, Ω-shaped inPteris wallichiana and horse-shoe shaped in others. InPteris vittata andPteris wallichiana pinna trace is extra marginal in origin while in all others it is marginal. Based on number and structure of vascular strand and nature of origin of pinna traces it is concluded thatPteris cretica andPteris vittata are relatively advanced over other species with simply pinnate fronds.Pteris wallichiana has been considered as highly evolved among the species investigated.
pp 409-413 December 1990
One set of specimens collected from higher altitudes of south India showing affinities withCyperus kurzii Clarke is described as new species together with its vegetative anatomy. The anatomical characters of this novelty differ in several details from those of species hitherto known anatomically.
pp 415-422 December 1990
Three new species belonging toPycreus Sect.Muricati are described and illustrated. The scanning electron microscopic studies of epicarpic surface markings reveal interesting details, real nature of the markings and differences among them. They are correlated with observations under binocular dissection microscope. It is now understood that transverse rugae and rugosely tuberculate condition of the epicarpic surface used as sectional characters seem to be nothing but the result of deposition of epicuticular wax. Interesting type of epidermal surface ornamentation is also recorded.
pp 423-433 December 1990
The status ofPycreus as an independent genus is confirmed. New combinations are proposed for two taxa originally considered as two distinct species ofCyperus and subsequently reduced to varietal status. They are described as two species ofPycreus based on new observations and illustrated. The speciesPycreus pumilus (L.) Domin is considereds. str. and its revised synonyms and those ofPycreus are given. Two new species are reported in Sect.Pumili Kükenth. A key to the identification of the species is presented.
pp 435-443 December 1990
Effect of cement kiln dust pollution on black gram (Vigna mungo) has been studied by comparing plants of polluted as well as from non-polluted areas. Due to cement kiln dust accumulation on exposed parts of the plant, there was a decrease in height, phytomass, net primary productivity and chlorophyll content. Quantitative estimations and histo-chemical localization indicate lowering of metabolites in dusted plants as compared to control one. In polluted plants, damaged leaves show increase in stomatal index and trichome frequency and decrease in stomatal frequency. Cement kiln dust accumulation on plant surface showed decrease in the number and size of flowers which finally affected the yield to a great extent in the dusted plants.