Y. Vaknin et al., FLOWERING SEASONALITY AND FLOWER CHARACTERISTICS OF LORANTHUS-ACACIAEZUCC (LORANTHACEAE) - IMPLICATIONS FOR ADVERTISEMENT AND BIRD-POLLINATION, Sexual plant reproduction, 9(5), 1996, pp. 279-285
The flowering biology and pollination ecology of Loranthus acaciae was
studied at Hazeva in the northern Arava Valley in Israel. Flowers at
anthesis had red anthers, a red stigma and a green corolla which turne
d red as a postfloral phenomenon. Their flowering period was approxima
tely 10 months long (from mid-June until mid-April) during which time
two main flowering patterns were distinguished. Some plants flowered t
wice a year, with separate summer and winter flowering periods; other
plants flowered continuously, with two peaks, one in the summer and on
e in the winter. Several significant differences between summer and wi
nter flowering and fruiting were found: (1) the summer flowering perio
d was shorter than that of winter, (2) flowering synchrony between ind
ividual plants was lower in summer than in winter, (3) in summer the p
lants produced a larger proportion of female flowers, whereas in winte
r most of the plants produced a larger proportion of hermaphrodites, (
4) in summer a limited number of plants produced smaller flowers while
the majority produced normal-sized flowers, whereas in winter the ent
ire population produced only normal-sized flowers, and (5) fruit set p
ercentage was lower in summer than in winter. L. acaciae was found to
be self-compatible, but, since it was not spontaneously self-pollinate
d, it showed high dependence on pollinator activity. In summer the flo
wers were visited by a wide spectrum of pollinators, both birds and in
sects, while in winter flowers were visited almost exclusively by the
orange-tufted sunbird (Nectarinia osea osea, Nectariniidae). These sea
sonal changes in flowering characteristics and pollinator activity cou
ld explain why reproductive success is higher in winter than in summer
.