Effects Of Betula Platyphylla Seeds And Seedlings By Spaceflight

The seeds vigor, physiological and photosynthetic characteristics were analyzed after seeds of four Betula platyphylla families were carried by spaceship. The results showed as follow:Effections of Betula platyphylla seeds didn't come to the significant level. Germination rate of every Betula family heightened, germination energy enhanced as a whole. And there were differences in the different families, for example, it was negative mutation in germination energy of HT98-3 and Seedling survival rate of HT98-4. So spaceflight can enhance the seed's vigor of Betula platyphylla..The results were obtained in the study that the positive mutation of HT98-1 was the most significant one in the three characteristics.There were some differences of treatment and ground control in SOD activity, relative electrical conductivity ratio, MDA concentration and Chlorophyll content, but didn't come to the significant level. The changes of SOD activity was from descend to ascend during growing in two years with ground control. Relative electrical conductivity ratio and MDA concentration were lower than the control during growing in two years. There were differences in the different families in chlorophyll content, when seedlings were two-year old, It was the same in every family. In a word, changes happened seriously in one-year old seedlings of Betula platyphylla after spaceflight, two-year old seedlings was not.It was suggested that space can make Betula platyphylla enhance antioxidant abilitu and faction of cell membrane.By the analyses of every photosynthesis characteristic, there were slight differences of treatment and ground control in every family, the one-year old HT98-3 was the same as the ground control of net photosynthesis rate in a day, and the others were higher than the ground controls at 10 to 16 in a day. In two-year old seedlings, the curve of HT98-4 was the same as the ground control of net photosynthesis rate in a day.There was a significant low at noon in HT98-1 curve of net photosynthesis rate, and it's variation range was at 14 in two-year old seedling.When PAR was under 100μmol·m^-2·s^-1the differences of treatment and ground control didn't come to the significant level. The maximum net photosynthesis rate were higher than the controls in HT98-1, HT98-2, HT98-4, the result showed that the three families were higher than controls in photosynthesis ability.Spaceflight made the ability of HT98-1 enhance in utilizing weak light, it showed in chlorophyll fluorenscemce of Betula seedling in two-year old after spaceflight, that there was positive in Fv/Fm of every family.the maximum variation range was HT98-2.There were differences of spacetreatments and ground controls in seedling height, ground diameter and fibre length. The seedling height and ground diameter were lower than thecontrols in one-year old seedlings, and there were some differences with controls in two-year old seedling. Except for HT98-4. theothers were higher than the ground control in the seedling height. It was a negative mutation. In ground diameter, only HT98-1 was a positive mutation. In the length of fibre, there was not a distinct trend.