M. Sandmeier et I. Dajoz, ALLOCATION TO REPRODUCTION IN PEARL-MILLET - CORRELATIONS BETWEEN MALE AND FEMALE FUNCTIONS, International journal of plant sciences, 158(5), 1997, pp. 510-518
We have described variation in allocation to male and female floral fu
nction in relation to plant size in an attempt to detect expected life
history trade-offs in pearl miller (Pennisetum typhoides, Poaceae). T
raits quantifying allocation to male and female functions (mean number
of pollen grains per anther, number of ovules, number of seeds, and m
ass of seeds per spike) were measured among tillers within plants and
among plants. Trait values varied significantly both among plants and
among tillers. Variation in male and female reproductive allocation di
d not result from differences in flowering phenology among tillers. Po
sitive correlations between allocation to male function (expressed as
mean pollen grain number per anther) and female function (expressed as
mass or size of seeds) were recorded at tiller and plant level. Since
in pearl millet male and female allocation are strongly positively co
rrelated with the size of the plant, new estimates of allocation to se
xual functions were used that were independent of possible size variat
ion observed among plants. If allocation to sexual function were expre
ssed per g dry mass, there were significant positive correlations betw
een allocation to the two sexual functions when female function was ex
pressed in terms of number of ovules or number of seeds per unit of bi
omass. On the contrary, there were significant negative correlations b
etween sexual functions when female function was expressed in terms of
mass of seeds produced per unit of biomass. Because ovule abortion ra
te was negligible in tile plants studied and because of strong develop
mental constraints on the floral structure of pearl millet (a spikelet
is constituted of a male flower with three stamens and a hermaphrodit
ic Bower with one ovule and three stamens), positive correlations betw
een number of seeds (or ovules) produced per unit of dry mass and male
function were unavoidable. However, plants that produced many pollen
grains per unit of aboveground dry mass also produced significantly lo
wer mass of seeds (per unit of aboveground dry mass) than plants that
invested less into male function. Allocation of large amounts of resou
rces into male function may impair the amount of resources available l
ater for allocation to female function, i.e., mass of seeds.