A Preliminary Study Of Mating System In Immature Plantation Of Heterodichogamous Cyclocarya Paliurus

Cyclocarya paliurus is a typical heterodichogamous species, which contains two mating types in populations: protogyny(PG) and protandry(PA). Flowering phenology of female and male functions segregation within PA or PG, while synchronization between PA and PG may greatly affect seed quantity and quality for C. paliurus population. To determine the sex-expression of C. paliurus, we monitored flowering phenology for 2 years(2014 and 2015), including the ratio of flowering phenotypes, the flowering order of male and female inter- and intra- two mating types, flowering duration and flowering overlapping characteristics based on 7-year plantations growing in Laying Taofeng and Hongyashan Farm. And analyzed the relationship of C.paliurus flowering and vegetative growth, seed sources and cultivation methods; Investigated the seed fructification, analyzed the seed plumess rate. The main conclusions were as follows:1.Flowering period of C.paliurus was from late April to late May, with fluctuation with environment factors changing. Durations of stigma receptiveness and pollen shedding lasted 9-19(21) days and 2-9 days, respectively. There were two categories, five flowering phenotypes in immature plantation: monoecious types containing protogyny(PG), protandry(PA) and synchrony(SC); unisexual type including female(F) and male(M).2.Observations of two plantations found the majority of F and less MO. In 2015,flowering rate in Liyang Taofeng was up to 73.2%,of which 43.4% individuals were F,28.8% individuals were MO, with the ratio of 1︰1.2 for PG and PA. However, flowering rate in Hongyashan Farm was only 38.6%, of which 20.3% individuals were F,16.7% individuals were MO, with the ratio of 1︰2.15 for PG and PA. Two consecutive year’s observations found the changes in mating category occurred mainly from UN to MO; the expressions of PA and PG individuals were stable, and inverse changes were very few.3.The male and female flowering peak periods of two mating types were synchronous and opposite.The period of stigams receptiveness of PG was almost synchronous with that of pollen shedding of PA, and similar phenomenon was observed on female flower of PA and male flower of PG. Within monoecious types, 52.2% individuals whose female and male flowering time were completely separated, and 47.8% individuals were partly(less completely) overlapping.4.Flowering or not, and flowering phenotype were obviously affected by nutrient accumulation of individual. The mean basal area of most NO plants were located in smaller range. With the increase of basal area, the ratio of NO decreased, while the ratio of FP, especially MO, increased progressively. The rank of flowering phenotypes based on average basal area is PG>PA>M>F>NO. Duncan’s multiple comparisons showed the average basal area of MO was significantly different from UN and NO. Among flowering category, no significant difference for average basal area was found among PG, PA and M. However, significant difference occurred between F and others(PG, PA and M types). Correlation analysis showed that flowering or not, sex system(UN, MO) were significantly correlated with tree height and basal area. However, no significant correlation was found between the expression of MO and UN with individual basal area and tree height.5.Correlation analysis showed that flowering situation of the plant was not significantly correlated with seed sources. However, the expression of UN was significantly correlated with planting density. More M type plants tends to appear in low planting stand, while more F type individuals are inclined to grow in higher density stand.6.seed stability of C. paliurus is low in immature plantation.Seed plumess rates from two stands are relative low. Though the average of seed plumess rate in Liyang Taofeng and Hongyashan Farm were 14.67% and 7.55%, the difference was not significant. Sililarity, the seed plumess rate of PA was slightly higher than PG, the difference was not significant. seed plumess rate among individuals of population was greater volatility, ranging from 0 to 50%.