Intra-inflorescence Variation And The Effects On Offspring Establishment Of Ligularia Virgaurea

Ligularia virgaurea is one of major weeds in the degenerated alpine meadows on the eastern Qinghai-Tibet plateau. Because it can grow clonally, the grass had been harmed seriously in resent decade. For long time, people like research the effects of environment factors on plants reproduction allocation and sex allocation, but neglect the inherent characters of them——Intra-inflorescence variation. We use L. virgaurea, one of the species in Ligularia Cass, and research the intra-inflorescence variation in flowers and seeds by sampling and investigate in field. Because ecologist were wild about the reason of intra-inflorescence variation only, but neglect the results that the phenomenon may bring on, so we keep on observing the effects of intra- inflorescence variation on offspring establishment by germination control experiment in lab and potted plants experiment in field, consequently find out the characters and strategies of sexual reproduction in L. virgaurea. Mostly conclusion as follows:1. There is intra-inflorescence variation in raceme of L.virgaurea individual, and it's not limited by different population. The capitula on the top of the raceme have more Ligulate flowers, less tubular flowers, and have distribute more resource and have bigger flower display; the capitula on the bottom of the raceme have reverse condition. Floral sex allocation was male-biased in bottom flowers.2. Seed production of L.virgaurea is affected significantly by position within an inflorescence, and it's not limited by different population. The trade of seed set and seed mean weight is top>bottom, ovule mean number is bottom>top, the middle position have most seeds. 3. The difference between different position within inflorescence is the inherent character of L.virgaurea, it's not change with different soil nutrients and light condition, but some overshadow is more propitious to exhibit positional effect.4. The germination strategies and seedling growth strategies are different between different positional seeds:the seeds on top capitula germinate late, germination period is short, and the leafstalk is short, on the seedling period, they distribute more resources on underground structure; the seeds on bottom capitula germinate early, germination period is long, and distribute more resources on overground structure, and they use longer leafstalk to increase height for lead up light resource to hold on growth and ward off other seedlings.5. Relative to the bottom seeds, the top seed can diffuse more far distance, and they have stronger ability to develop to new habitats. The upper R/S and Photosynthetic rate enhance the ability of seedling establishment, so they have more contributes on renew and recruit for nature population.6. The positional effects not only influence seedling establishment, but also influence the leafstalk length of second-year old plants under some shadow condition, the variety is bottom>top, this means that under the insufficient light condition, positional effects still have function to adjust the growth strategy of the plants which grow from different positional seeds within inflorescence.