| Disanthus cercidifolius Maxim. var. longipes H. T. Chang, a plant speciesthat only occurs in a few counties in Hunan, Jiangxi and Zhejiang Provinces and with relatively small numbers of individuals, is recorded as the 2nd Class endangered species for conservation in China.According to the data from the field observation, we studied the flowering phenology variation, and the temporal as well as spatial variations of reproductive modules in the natural populations of the species. The variations in morphological traits, flowering phenology and reproductive success of this species were also studied. The flowering course at individual level was observed and the data on flowering onset, duration, mean flowering amplitude (flowers/plant/day) and end of flowering were registered. Then the relative flowering intensity and synchrony indices were calculated. The relationships among onset, duration, flower and fruit set, the correlations between starting date and duration, flowering and duration, the phenology index and fruit set, respectively, in the wild population were analyzed.With the help of the field investigation and based on the out-crossing index, pollen-ovule ratio, emasculation, bagging and allozyme analysis, we studied the floral syndrome and breeding system of D. cercidifolius Maxim. var. longipes H. T. Chang among artificial populations and natural populations in Mt. Jinggang, which is one of the National Reserves in Jiangxi, China. The behaviors and their pollination efficiency of the pollination medium of the species were investigated at the same time.The traits were also carried out to study the effect of pollens and resource availability on female reproduction, and the reproductive mechanism of such phenomena called as "mass flowering but few fruiting" in D. cercidifolius Maxim. var. longipes H. T. Chang was discussed.Photosynthetic function traits of D. cercidifolius Maxim. var. longipes H. T. Chang inrelation to light heterogeneous habitats and its acumination mechanism were studied by measuring the gas exchange and chlorophyll fluorescence. We also reported the numeric dynamics of populations of D. cercidifolius Maxim. var. longipes with the helps of static life table, fecundity schedule, Leslie matrix and time sequence analysis based on the over-all investigation of age structure, seed production and natural seed germination rate etc.. The results are as follows:There are certain degree of differences of the flowering phenology among the populations in different communities, e.g., in pure forest the average flowering duration of individuals is the longest with 75d, while the flowering synchrony is the lowest with only 0.717; but in the bamboo forest the flowering duration of individuals is the shortest with only 47d, while its flowering synchrony is the highest.The numbers of the reproductive branches and the inflorescences increase with the individual age increases, and reach the peak at the age of 30 - 35a. At elevation of ca. 810m, the numbers of the reproductive branches and inflorescences per individual reach the peak, and there are significant differences among the crown levels. The reproductive branch number of individuals and the inflorescences per reproductive branch are the highest in the pure forest with 411.39 and 7.857 respectively, while the inflorescences per reproductive branch in the bamboo forest are notably lower than those in other communities.The abortive ratio of reproductive modules of the young individuals is higher than that of the older ones in all the flower-bud, flowering and fruit phases. The abortion of reproductive modules shows no correlation with their distributed elevations, while some correlations with their developing time, distributed crown levels and communities. The major factor influencing abortive ratio of individual reproduction modules is probably the illumination condition in the distributed communities.In D. cercidifolius Maxim. var. longipes H. T. Chang, two axillary inflorescences are often opposite with each other at the same node. Each inflorescence has two opposite bisexual flowers without pedicels. Each flower is ca. 15 mm in diameter and lasts 6 to 7 days. The flowering span of the individuals is about 49~55 days. On the day of anthesis, the styles are longer than filaments; the length between anthers and stigmas is about 1.02mm. The colour of petals changes from light red to brown. The stigma changes from light green through pale yellow, to brown, then to black at last. The anthers dehisce in orderof priority. Two of the anthers whose dehiscence pattern is longitudinal and synclinal upward always dehisce at first, than the others. The pollens form an obvious "pollen circle" surrounding the stigma when the anthers all dehisced. With regard to the flower morphology and dehiscence, the typical flowering process for a flower can be divided into 4 periods, i.e., "Pre-dehiscence" in which two filaments stretch out but without dehiscence, "Initial dehiscence" in which one or two anthers are dehisced after two days of flowering, "Full dehiscence" in which from the third to fifth day of flowering three to five anthers are dehisced and the color of the stigma changes to yellow, and the "Withering" in which all anthers are dehisced with some anthers withering and the color of some stigma changing to brown or black yellow from the sixth to seventh days.In the Caijiatian population, the time courses of flowering were more or less similar over four years. In 1999 and 2000 the proportion of open flowers increased gradually to a peak, and then declined rapidly over the subsequent weeks. In 2001 and 2002 the proportion of open flowers increased rapidly to a peak, and then declined gradually. In the Ciping population the curve was "bell-shaped". In the Ciping population flowering started on September 12th in 2002, while in the Caijiatian population flowering started between September 17th to 22nd. The duration of flowering in a population lasted 63-71 days. The flowering lasted significantly longer in the Ciping population than in the Caijiatian population.The relative flowering intensity shows two major peaks: one from 20% to 40%, and the other from 70% to 90%. Though this phenomenon is not consistent with some other studies, it has some evolutionary significance for the studied species.The correlation analysis among onset, duration, flower and fruit set shows marked relations among them. There are significant negative correlations between onset and flowers, and duration and fruit set, and significant positive correlations between flowers and duration. The population with an early starting date shows a longer duration than the population with later starting date. The population with more flowers shows a longer duration than that with less flowers. There is higher fruit set in the population with an early starting date and longer duration than in the population with a later starting date and shorter duration.The differentiations between the two populations and similarity within the same population in terms of the flowering phenology suggests that the timing of an individual's flowering may be determined largely by relatively fixed characteristics of its microhabitat and (or) by genetic factors. This also reflects the genetic differentiation among populations and genetic similarity within the same population. As an endangered plant, Disanthus cercidifolius Maxim, var. longipes exhibits a so-called "Mass flowering" pattern, which may be regarded as an adaptive strategy to ensure its reproductive success.The flower is ca. 15 mm in diameter. There are both temporal and spatial isolations of male and female organs within the same flower. It is protandrous with the outcrossing index of 4. According to criterion put forward by Dafni, the breeding system of this species can be determined as outcrossing with partly self-compatible and needs pollinators during the pollination. The pollen-ovule ratio (P/O) is 1 250. Based on Cruden's criterion, the breeding system is termed as xenogamy.Based on the results of emasculation, bagging and artificial pollination of this species, we know the seed productions vary from case to case. There are no seed production when the inflorescences are with emasculation, bagged and no pollination; and few seeds when unemasculation, bagged and free pollination. In the treatments that the flowers are emasculated, unbagged and free pollination, or unemasculation, unbagged and free pollination, or emasculation, bagged and hand self-pollinating, the inflorescences can produce some seeds. In the treatments of emasculation, bagged and hand geitonogamy or hand cross-pollination, the inflorescences can produce more seeds, but its producing ratio is still low from 28.50% to 45.01%. There is no agamospermy, and the outcrossing is the main form in the breeding system of the species.This species maintains relatively higher level of genetic variation as compared with other species at normal condition. The proportion of polymorphic loci (P) is 62.70%, the average number of alleles per locus (A) is 1.63, and the mean effective number of alleles per locus is 1.55. The Gsr is only 0.09. The results show outcrosssing is predominant in the breeding system of the specie.The pollen competition may be one of the major causes resulting in the endangered situation of D. cercidifolius Maxim, var. longipes H. T. Chang.The major pollination insects of D. cercidifolius Maxim, var. longipes H.T.Chang are Episyrphus balteatus De Geer, Scaptodrosophila coracina Kikkawa et Peng, Polistes olivaceus De Geer, Apis cerana Fabricius, Nezara viridula Linnaeus and Coccinella septempunctata Linnaeus, et al. The number of Scaptodrosophila coracina Kikkawa et Peng was larger than other insects. Scaptodrosophila coracina Kikkawa et Peng was crawling on flowers, but hided themselves in the bracts at the base of peduncles or in the shading spots in other flowers only when the flowers were exposed to the hot sunshine. Episyrphus balteatus De Geer has higher visiting frequency than the other insects except Scaptodrosophila coracina Kikkawa et Peng. The pollens could be seen at its mouthparts -and trunk legs. Scaptodrosophila coracina Kikkawa et Peng and Episyrphus balteatus De Geer were the most important and efficient insect pollinators, the rest were inefficient pollinators. The index of wind pollination efficiency is only 0.0012-0.0015, which shows that transfer efficiency of wind is very low. But it is a reproductive assurance while absence of insect pollination in some years. It is an adapting behavior and reproductive strategy with "Mass flowering", and "few fruiting" may be the reproductive result because of the shortage of pollination media and the low efficiency of pollination. The shortage of pollination media and the low efficiency of pollination may be the major causes leding to the endangered situation of D. cercidifolius Maxim, var. longipes H.T.Chang.Pollens from different sources have significant effect on fruit set and seed set of D. cercidifolius Maxim, var. longipes H. T. Chang. It was pollen source, while not pollen numbers, that significantly effected on the reproduction of this species. In natural populations, producing one fruit needs about 54.8 flowers, and one satiation seed needs about 6.6 flowers or 83.19 ovules.Fertilizing was propitious to the flowers developing. After fertilizing, the abortion rate of flower buds was decreasing, while the flowering rate increasing. And the fruit set and seed set were also significantly increasing, while abortion rate of fruit was significantly decreasing. With the increasing percentages of cutting leaves, the fruit set decreased, but the abortion rate of fruit showed no significant differentiation among treatments. After cutting the puny branches and disease, insect or pest infected branches, the flowers hadsome decreasing, but both the fruit set and seed set increased significantly. After removing some flowers, the fruit set calculated with respect to the number of flowers remaining after treatment increased with increasing of percentages of flower removal, whereas fruit set calculated with respect to the initial number of flowers remained constant, and the mean weights of per fruit and per seed all decreased significantly.Sufficient spatial or temporal heterogeneities in nutritious levels might allow limitation of seed set by resources and pollen in a natural population, supplying resources may indirectly effect on pollination by increasing the attraction of the flower to pollinators. There were very low fruit set and seed set in natural populations of D. cercidifolius Maxim, var. longipes H. T. Chang. The combination of "selection abortion hypothesis", "ovary reservation hypothesis" and "male function hypothesis" seem to be the most likely explanations for the reproductive strategy of"mass flowering, few fruiting" of this species.In different habitats, the net photosynthesis of this species shows different traits: in the pure forest of the species and evergreen broadleaved forest, it has "Midday Depression of photosynthesis" phenomenon because of the stomatal limitation and the temporality descend of PSII function, moreover, in the bamboo forest, it shows a pattern "single apex curve". With the increase of light intensity in the daytime, the photochemical quenching (qP) and non-photochemical quenching (NPQ) will increase, but the OPSII will decrease, and will be restrained in midday, and then recovery.Under different light intensity, the distribution proportion of the light energy absorbed by the leaf varies obviously. In the pure forest of the species and evergreen broadleaved forest with high light intensity, along with the increase of light intensity in the daytime, the allocation of light absorbed by PSII antennae to the photochemical reaction decreased, but the allocation of absorbed light to thermal dissipation and excessive energy increased clearly. But the increase only happens to the midday because of the rapidly increased light intensity, and in the afternoon, with the decrease of the light intensity, it can resume perfectly. In the bamboo forest with low light intensity, most of the absorbed light energy is used on PSII antennae to the photochemical reaction, the allocation of absorbed light to thermal dissipation has hardly change, and the excessive energy of reaction center remains at a very low level in a day.
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