Preliminary Study On The Enlargement Mechanism Of Lotus Root Rhizome

Enlargement rhizome is the leading product organ of lotus root. It will provide theoretic bases for lotus root cultivation and production to know the development mechanism of enlargement rhizome. However, the research about this is in its infancy. We studied the dynamics of the rhizomes and leaves growth and dry matter accumulation and distribution, and the changes of the morphology of a cell during lotus root rhizome enlargement, and the reasons of environment factors, and the effects of different plant growth regulators on lotus root rhizome enlargement. Materials adapted in this paper were 'E Lian No. 4','E Lian No. 5' and 'Xin Yi Hao' that were mid-matured cultivars and the mainly adapted cultivars in lotus root cultivation. The results were shown as follow:1. At the process of lotus root growth and development, the change trend of fresh sample mass per plant accorded with the one of dry sample, which was "slowly and gradually increasing before lotus root rhizome enlargement—mushrooming during lotus root rhizome enlargement—slowly and gradually reducing after lotus root rhizome enlargement". The change trend of leaves and rhizome was similar to the one of plant, but the content of enlargement rhizome increases consistently, and there was a sharply increased process in mid-period of rhizome enlargement, and the percentage of dry matter distributed to enlargement rhizome gradually increased. Leaf area and net assimilation rate increased consistently with processing of growth and development, and their max value (3205.4cm², 8.40)came forth until mid-period of rhizome enlargement.2. Lotus root top bud took out rhizome under the ground after it germinated. Later, the internode of rhizome elongated quickly, and got fatter at the same time. The internodes above three kept same thickness until rhizome enlargement. The rhizome directed downward from level direction when it enlarged (about the 8^th internode), and its internode shortened and got fatter quickly. After 30 days, the enlargement rhizome matured completely, in the meanwhile, its top bud turned upward. Generally, it took 10 days to form a internode of enlargement rhizome. The longitudinal growth of enlargement rhizome was caused by the elongation of parenchyma cells, but the transverse growth of enlargement rhizome was caused by the increase of parenchyma cells layer and diameter, and the transverse growth of enlargement rhizome was mainly caused by the increase of parenchyma cells diameter in the anaphase. In addition, the parenchyma cells of rhizome was strip-shaped. The strip-shaped cells lied outside and the global cells lied inside when the rhizome will enlarge. The parenchyma cells of enlargement rhizome was mostly global. There were a small quantity of starch grains in the parenchyma cells which lied outside of enlargement rhizome. Therefore, the starch grains began to accumulate from outmost ring to centre in the beginning of enlargement.3. Different sowing date had considerable positive influences on plant height, leaf number and leaf area. When the lotus plant was sown in late date, plant height, leaf number and leaf area took on downtrend, which wasn't favorable for extending resource and led to reduce the yields. Therefore, late sowing (generally before the end of May ) was favorable for increasing yields in growing season. Lower temperature and shorter day-length could promote rhizome enlargement, but this affect could cooperate with the other factors, for example, nutrition etc.. Meanwhile, there were some environmental factors to promote rhizome enlarge: (1)genotype—the lotus root cultivars with different mature date. (2)planting density—higher planting density was favorable to enlarge for lotus root rhizome. (3)adversity—A late spring cold period and herbicide could result in rhizome enlargement by itself.4. GA₃ could promote offshoot growth and increasing of leaf number, plant height and rhizome weight significantly. But 6-BA could promote increasing of leaf number, leaf size and extending of rhizome internode to some extend, and increase 22.0 leaf/plant,25.2cm,97.8g/plant than CK. CCC and PP333 could inhibit the germination and growth of leaf and rhizome partly, but CCC could increase leaf size(increase 52cm" than CK) and darken the leaf color. CCC and 6-BA , especially CCC, could promote the rhizome enlarge but GA3 inhibit or postpone the rhizome enlarge.