Abstract:

In this study, we investigated resources allocation in intra-inflorescence

of Ligularia virgaurea in different habitats and population densities based

on the characters of reproductive allocation that have been studied. The material

we studied was collected from Nima (101°53′ E, 35°58′ N, altitude 3 500 m) in

Maqu county, Gansu province, in the first turn of Yellow River, North-East region

of Tibetan Plateau. This region belongs to the alpine meadow rangeland type.

The plot contained habitats of different degrees of degradation. L. virgaurea is

a perennial herb of Compositae. The flowering phase lasts from July to August,

with blooming starting at the top of the raceme. The frutescence is in September,

about 10 days. It is the dominant weed in alpine meadow now because of the toxic

milky material, selective predation and over-grazing by livestock. The aim of our

research is to reveal the reproductive strategies of L. virgaurea at the

level of the inflorescence. 

During the latter period of seed maturation of L. virgaurea in September 2000,

we sampled randomly from three habitats, floodland, hillside and lowland, and two

populations of different density in each habitat. There were 10-16 quadrates per

plot, 1-3 seed producing ramets per quadrate were sampled, and brought to the

laboratory. The vegetative and reproductive structures were separated, heated 24

hours in 75 ℃ drying oven, and weighed using an electronic balance (g/10 000).

The ramet, raceme, capitula of different positions on the raceme, and the number

of capitula per raceme were measured. The data were analyzed by ANOVA and linear

regression. The measures are: the size of ramet and raceme represented by their

biomass; mean weights of capitula (the ratio of biomass and numbers of capitula

per raceme); the available capitula of top, middle and bottom represents

separately the top, the position of 1/2 RI and the bottom; the resource allocation

of capitula at different position means the biomass percent of capitula /raceme;

available capitulum means it could produce seeds, unavailable capitulum means it

did not.The results show: 1) different habitats or population densities differ

in resource investment of raceme and capitula of different positions within raceme,

and it exhibits some trends as follows: floodland > hillside > lowland, uncovered

land > covered land, and low population density > high population density; 2)

although most of the correlation coefficients are small, there are negative

correlations between the characteristics of racemes (such as the size of raceme

and capitula, the number and mean weight of capitulum) and population densities,

and no correlations between the size of capitula of different positions within

the raceme and population densities; 3) there is a position-based effect within

inflorescences, such as the significant decrease in the resource investment

between the early-formed or top capitulum of the raceme and later-formed bottom

or middle capitula of the raceme; 4) there are significant negative correlations

between the size of the raceme and the allocation of capitula at different

positions of the raceme.