Number Of Capitula Research Articles

Effect on the growth and yield due to the aphid,Dactynotus sonchi Linn. in safflower

Field experiments were conducted in paired plots to assess the losses due toDactynotus sonchi Linn. in the yield of safflower in two successive winters 1977–78 and 1978–79. The percentage losses in the number of capitula per plant and in seed yield have been calculated and discussed. Excepting the secondary branches per plant, all the yield contributing characters and the seed yield showed significant differences in treated and untreated plots.

THE GENECOLOGY OF LAWN WEEDS. IV. ADAPTIVE SIGNIFICANCE OF VARIATION IN BELLIS PERENNIS L. AS REVEALED IN A TRANSPLANT EXPERIMENT

SUMMARYIn order to study the adaptive significance of variation in Bellis perennis L., an experiment was carried out in which plants from 19 populations – drawn from four habitat groups (I, lawns; II, grazed areas; III, seasonally mown and/or grazed areas; and IV, areas not seasonally reduced in height by grazing and/or mowing) ‐ were transplanted into a lawn subjected to regular mowing. Vegetative growth (as revealed by increment of plant width, dry wt and number of rosettes) and reproduction (as estimated by the number of capitula which survived mowing and produced fruit) were investigated over a 17 month period. As most plants in the experiment grew successfully and approximately 60 % of the 95 individuals (including plants from all four habitat groups) produced fruiting capitula, there was no evidence of distinct ‘races’ of B. perennis in the regularly defoliated habitats of lawn and pasture studied. However, the more successful plants, in terms of numbers of fruiting capitula, were found in samples collected from lawns and Port Meadow: pasture. Four individuals (three from lawns and one from Port Meadow) yielded approximately 50% of all the capitula which fruited. Within ‘successful’ populations there were plants which produced few or no fruiting capitula. Various hypotheses are presented to account for population variation.Estimates of coefficients of selection, comparing different features of growth and reproduction, may yield different values. For example, even though different individuals are apparently equally successful in vegetative growth under experimental conditions, i.e. with coefficients of selection of 0, a comparison of reproductive success for the same plants may give a value of 10.

Pollination Mechanism and Inbreeding Depression in Niger (Guizotia abyssinica Cass.)

Self fertilization resulted in 30 per cent of pollen sterility and 80 per cent of seed sterility in niger. Germination and survival of seedlings resulted from selfed pro- genies were very low. There was considerable reduction in yield attributes like number of branches and number of capitula which depressed the yield of self pollinated pro- genies. The inbreeding depression in vield was as high as 91 per cent. In view of the high self incompatibility, sibmating may be resorted to for developing inbred lines. By sib mating it should be possible to develop lines with desired attributes without sacrificing general vigour and production.