Studies On Pollen Dispersal Characteristic In Seed Orchard Of Pinus Elliottii

Slash pine (Pinus elliottii) grows fast and has wide adaptability. It's considered as excellent tree resources of pulp, timber and pine resin high yield and quality. So it has been widely used and established a number of seed orchard of Pinus elliottii. Seed orchard is the base of producing high genetic quality seeds, but the production of seed orchard of Pinus elliottii is low, and it fruits unstable in reality. Those become an important issue to be resolved. Therefore, mastering the flowering and fruiting pattern of the clone in seed orchard is an indispensable part to establish or to manage the seed orchard or to test the progeny, which also plays an important role in improving the yield and quality of seed orchard. In this paper, the process of morphological development of male and female cones, the distribution of male and female cones in mother tree crown, the distribution of pollen in space and time during the pollen dispersal, the output of pollen and ovule among different clones and other aspects are discussed for the seed orchard of Pinus elliottii. We made conclusions as follows:Pinus elliottii has formed its unique rhythm of growth phenology in the long-term adaptation to the environment. And it has a unique morphological characteristic at the flowering period, especially at the flowering stage of female cones. We can divide it into seven periods artificially:0 period,1 period,2 period,3 period,4 period,5 period and 6 period, and of which 4 period and 5 period can be considered as the best period for pollination of female cone of Pinus elliottii.The period of male cone pollen dispersal can be divided into four stages, which is initial stage, flourish stage, final stage, and finishing stage. The male cone of Pinus elliottii has formed the morphological mechanism being good for pollen dispersal and protecting pollen from raining. The female cone has also formed the morphological mechanism which can help ovule to be pollinated and fertilizing well.The distribution of male and female cones in the crowns have stratification phenomenon. Male cons are mainly located in the middle part of tree crown to the bottom and female cones in the middle to the top.Compared the two method to measure the pollen production of pollen sac, it shows that the data measured by the water culture method is more accurate than that measured by cleaning method and the system error is smaller. The number of pollen production per microsporangium measured by water culture is 3600.4, the number of pollen per mother tree is 3.36×1010, and the number of pollen of the whole seed orchard is 1.88×1014. The number of ovule per female cone is 162.2, per mother tree 1.0×105, and the whole seed orchard 6.5×108. In theory, the whole seed orchard can produce 22750 kg of seed.Seed orchard of Pinus elliottii has some rhythm in time and space during the pollen dispersal period. From the point of time, we can find that Pinus elliottii in Guangdong usually begins to flowering from late January to early February and lasts about 20 days. The beginning time, ending time and lasting time is affected by climate dramatically. There is a peak time during the whole period, which usually last three or five days. The pollen quantity in the air everyday is different, which is extremely significant. But in general terms, pollen dispersal has a rhythm of low-high-low during the whole period with the time going. There is a peak time in a day during the peak time of the whole pollen dispersal period, it always appears in 10:00-16:00, which is affected by weather of that day. It has a rhythm of low-high-low with the time going in a day. The pollen distribution in the seed orchard of Pinus elliottii presents uneven through the horizontal space, but it shows a certain rhythm through the vertical space, which shows a decreasing trend in pollen quantity from the ground,1/3 of tree height,2/3of tree height,1 time of the tree height to 4/3 of tree height.The results is that Ra value is 23.7 to 39.6, Rm value is 17.6 to 26 in 2010; Ra value is 46.3 to 77.2, Rm value is 35.1 to 70.2 in 2011. The accumulation of pollen quantity during the pollen dispersal period is 17.6 to 77.2 times of that of appropriate pollination level. It shows that pollen density can ensure the pollination in current seed orchard of Pinus elliottii, but the pollen production is too much high, it should be reconstruction by introducing partial female clones of Pinus elliottii or using some technology to increase the number of female cones in order to produce more seeds. Besides, it still needs artificial pollination because the pollen of Pinus elliottii has gasbag, which can be carried by the wind easily.