Caryopsis Development Of Rice

Two varieties of high-yielding rice breeded by LiXiaHe region agricultural science institute were used in this experiment to study development of rice caryopsis, the dynamic changes of its physiological activities during its development and the source of filling material in rice caryopsis. In this experiment, I chose different stages of the vegetative organs and caryopsis, used resin slicing, scanning electron microscope, fluorescence microscope to observe the microstructure organ of vascular bundles and observe the development of caryopsis endosperm, embryos, rind etc. The main research results are as follows:1. After fertilization, moisture content of caryopsis was high, fresh and dry weight increased rapidly, the starch, protein and lipids content of caryopsis increased rapidly and embryo development was also fast. With the increasing of the caryopsis development days, water content decreased, when the water content reduced to20%, filling basically stopped; fresh and dry weight of the increasing trend has been slowing. Starch, protein and fat increased until the filling stops; embryo fully developed, has the germination ability of the individual. Dehydrogenase activity and moisture content of caryopsis have a certain correlation. With the decline in moisture content, dehydrogenase activity was gradually decreased.2. Clear the embryo development.0to10hours after pollination, egg and sperm fusion form a zygote with polarity.10hours after pollination, zygote top cell and basal cell formed the original embryo. These two cells are arranged up and down, oblique splited to form four cells of the original embryo, and then the four cells began to split in all directions. About2to3days after flowering, these cells splited into a multi-layered spherical embryo, then was pear-shaped embryo. About4days after flowering, embryo elongated and differentiated the ventral groove, and then formed of apical meristems. About5days after flowering, coleoptile, radicle primordia and apical meristem were all appeared.6to8days after pollination, some nutritional leaves of apical meristems differentiated the number1full leaf primordium and scutellum growing up.10days after pollination, number2full leaf primordium appeared, crown and coleorhiza radicle also appeared, the back of scutellum began to differentiate the absorption layer, vascular that join the scutellum and plumule general differentiated completely.11～12days after flowering, embryo cells were almost no proliferation, number2full leaf primordium’s differentiation processes remained in the small state, this time the embryo was almost complete differentiation, already had a good germination capacity. About14days after flowering, with the expression of mature-related gene, embryo slowly enriched, and finally with the dehydration, embryo’s volume shrinked, and went into dormancy.3. Clear the source and the transit way of storage substance. The substance in caryopsis mainly derived from the photoassimilate after heading and the temporary storage from stem and leaf sheath before heading. Throughout the body of rice plants, the vascular system is the main conducting tissue, beared long-distance transport function in vivo. The distribution and link of vascular bundles system in rice plants was an interconnected organization, the ground organs (leaf, leaf sheath and stem) had two kinds of vascular bundles, and the underground organs (roots) have one type of vascular bundle. Leaves were the main places of photosynthesis in rice, perform the exercise of the "source" function in the "source, flow, bank" system. Vascular bundles in stems were the transport corridors of water, mineral and organic nutrient, perform the exercise of the "flow" function.Nutrients into the caryopsis were vascular bundles in the back of the caryopsis. Caryopsis dorsal vascular bundle and the endosperm were not direct contact; between the two was nucellus tissue. Nutrients transported to the ovary by the mother first unloading to the dorsal vascular bundle, split-flow by apoplast in the outside of nucellus tissue. Part of the nutrients through the dorsal aleurone layer cells unloaded to endosperm, the other part of nutrients transported to the outside of endosperm by peripheral around the endosperm, and then by different parts of aleurone layer cells transported to the inward endosperm.Nutrients transported to embryo mainly through endosperm tissue. During the development of embryo, endosperm tissue adjacent to scutellum provided nutrients to it.