Plants of white clover (Trifolium repens) were grown under canopies of clover leaves floating on shallow glass tanks of water and their growth was compared with that of plants under canopies of black polythene 'leaves'. The experimental design allowed the growth of the clover plants in canopy filtered light to be compared with that in unfiltered light at different intensities of Photosynthetically Active Radiation (P.A.R.). The effect of canopy filtered light was to exaggerate the effects of reduced P.A.R. especially in promoting petiole extension and inhibiting stolon branching. Two clones of white clover differed in their responses to P.A.R. and to light quality and there were significant interactions between the effects of the intensity of P.A.R. and type of shade. It is argued that it may be important for both ecologists and plant breeders to recognise the role of radiation quality in regulating the dynamics of pasture.

Transplants of white clover (Trifolium repens L.) were grown isolated from each other and in pairs placed at different distances apart. The paired plants developed asymmetrically and at the interface between paired clones both the density of nodes and of stolons appeared to reach ceiling values that were of the same order as those achieved in isolated clones. It is argued that the growth of plants of T. repens is controlled by the local conditions experienced by the plant parts and not by integrated growth of the whole. Transplants of three different genotypes of T. repens, which differed in growth form, were grown as neighbouring pairs and the calculated asymmetry of the plants was used to compare their mutual aggressivenes. The more compact (phalangeal) genotypes induced greater asymmetry in their neighbours than the more diffuse forms.

Anthocyanin pigmentation is a prominent feature in the adventitious roots Of Metrosideros excelsa. We describe the histological distributions and chemical nature of anthocyanins in these roots, and quantify their antioxidant activity. Anthocyanins were present in one or more cell layers of the root cap, epidermis, hypodermis, and cortex. A narrow band immediately behind the root apex was usually anthocyanin free. Photosensitivity of anthocyanin biosynthesis was evident both for adventitious roots and for plagiotropic roots exposed at the soil surface. The anthocyanins were cyanidin-and delphinidinbased. Methanolic extracts of the roots did not show a direct relationship between anthocyanin concentration and antioxidant activity. The possible function of anthocyanins in these roots is unknown.Abbreviations PC = paper chromatography, TLC = thin layer chromatography, DPPH = a,a-diphenyl-P-picrylhydrazyl, Cy = cyanidin, Dp = delphinidin, Pg = pelargonidin, Pn = peonidin, Pt = petunidin, Mv = malvidin

The tropical fresh water fern salvinia(Sa1vinia mlesta D.S. Mitchell) ' is a problematic weed and is being controlled biologically by the introduction of a weevil, Cyrtobagous salviniae. The plant consists of three morphologically different growth forms; primary, secondary and tertiary, duringitsgrowth. The present paper describes how the initial density of primary stage plants affected its morphological plasticity. Primary stage apical cuttings consisting of three ramets (uniform in size) were selected and were grown at densities of 16,400 and 800 ramets per square metre. The growth and morphological changes were observed for a period of 100 d. Plants remained at their primary stage under the lowest density and they transformed from primary to secondary and then to tertiary growth stages at higher densities. There were significant differences between the growth forms and their growth.

Single rarnets of the tropical, floating, freshwater, aquatic weed, Salvinia molesta a t its tertiary stage were grown at initial densities of 16 plants, 80 plants and 160 plants per square meter, in a pond. Growth parameters were measured for each plant separately after 6 wks. Results showed that thenumber of nodes and leaves, the mean internodal length, the length of whole stolons, the dry weight of plants, the number of branches and the percentage branching decreased significantly (p<0.05) with increasing initial density of ramets.