Floral anthesis generally occurs at night in polyembryonic cultivars (Wagle, 1929; Torres, 1931; Galang and Lazo, 1937; Pimentel et al, 1984) and at night or early morning in monoembryonic types (Popenoe, 1917; Musahib-ud-din and Dinsa, 1946; Singh, 1954a; Randhawa and Damodaran, 1961a, b). Subsequent dehiscence of the four-lobed anthers occurs during the daylight morning hours revealing pale blue pollen grains (Torres, 1931; Galang and Lazo, 1937; Mallik, 1957; L.B. Singh, 1960). Anthesis and anther dehiscence are delayed by low temperatures or overcast days (Singh, 1954a; De Wet and Robbertse, 1986a). Dehiscence is also delayed by high RH, and pollination occurs primarily around midday (Mallik, 1957; Randhawa and Damodaran, 1961a, b).
Stigmas are receptive from c.18 h prior to anthesis to at least 72 h after anthesis with optimum receptivity within 3 h from anthesis (Popenoe, 1917; Wagle, 1929; Sen et al., 1946; Singh, 1954a; Spencer and Kennard, 1956; Randhawa and Damodaran, 1961a, b; Gunjate et al., 1983; Pimentel et al., 1984; Robbertse et al., 1994). Receptive stigmas are shiny and white-green, whereas non-receptive stigmas are desiccated and yellow-brown. Pollen germination generally occurs within 90 min of deposition, although the percentage germination of pollen deposited on stigmas is relatively poor (Singh, 1954a; S.N. Singh, 1961). Pollination is initiated by the formation of two unusual protuberances that meet to form a bridge or ponticulus connecting the dorsal side of the ovule with the ovary wall in line with the base of the style (Joel and Eisenstein, 1980). The ponticulus may guide the elongating pollen tube to the ovule. Ovule fertilization occurs 48-72 h after pollination (S.N. Singh, 1961; Ram et al., 1976). Both zygote cell and endosperm nuclear division appear to rest for about 2 weeks following pollination despite cell division and growth of the ovary (Sharma and Singh, 1972; Ram et al., 1976). A description of embryo development is presented by U.R. Singh (1961). Application of B may improve stigma receptivity, pollen tube germination and growth and ovule fertilization (De Wet and Robbertse, 1986b; Robbertse et al., 1988; De Wet et al., 1989) as well as fruit development (Chen, 1979; Robbertse et al., 1990); however, Jutamanee et al. (2002) could not verify the effect of B.
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