Research On Dormancy And Germination Physiology In Barnyard Grass And Lettuce Seeds

The dormancy and germination of seeds were influenced by their structural andenvironmental factors. In this study, we used the barnyard grass and lettuce seeds asresearch material. The barnyard grass was the weed of rice field, the rice seeds wereeasy to germinate in the high temperature and rainy season, but the seeds of barnyardgrass were not germinated. Now, the factors which effected the dormancy andgermination of the barnyard grass were not be known clealy, and is it related to theenzymes activities of the degradation of cell wall. In addition, the germination of manycrops seeds were inhibited by temperature in tropical areas, they were not germinated orin the same time. the lettuce liked growth in the cool climate, it was not tolerence to hot,however, it sensitived to light. The lettuce had the typical thermoinhibitioncharacteristic, and it was suit for research the influence of temperature on the dormancyand germiantion of seeds. Nitrate can released the thermoinhibition of lettuce seeds,ABA can inhibited the effector of nitrate. But it not were known about the nitrteregulated the biosynthesis and metabolism genes of ABA and GA. We investigated theeffect of the temperature, cutting seed coat, GA,6-BA, after-ripening andcold-stratification to the barnyard grass seeds, and the different of β-mannanase,β-mannosidase and α-galactosidase activities on the germination of the barnyard grassseeds, and the after-ripening and cold-stratification were effected the activities of thethree enzymes, at the same time, we investigated the effect of temperature and light tothe lettuce seed, and the function of nitrate to the thermoinhibition of lettuce seeds, andthe nitrate regulated the expression of ABA and GA biosynthesis and metabolism geneson the germination of lettuce seeds. Get the following conclusions,(1) The germination of the barnyard grass seeds was inhibited by the temperature,the optimum temperature was20oC, when the temperature up or down20oC wouldinhibited the germination of the barnyard grass seeds.(2) Cutting the seed coat was promoted the germination of the barnyard grass seeds,so the seeds had the physical dormancy. Following the time of the treatment ofafter-ripening and cold stratification to extend, the germination of barnyard grass seedswas promoted. After the300d of the treatment of after-ripening, the germination of thebarnyard grass seeds was decreased; the germination of the cold stratification treatment360d of the barnyard grass seeds was lower than the cold-stratification treatment300d,so, the seeds also had the physiological dormancy.(3) The plant hormone of GA and6-BA did not promoted the germination of thebarnyard grass seeds.(4) On the germination of the barnyard grass seeds, the activities of-mannanaseand-mannosidase was increased by the incubation time, but the activity of the -galactosidase had no significance changes by the incubation time. After-ripeningincreased the activity of the-mannosidase, and the cold stratification increased theactivity of the-galactosidase, so after-ripening maybe effect the activity of the-mannosidase to effect the germination of the barnyard grass seeds; cold stratificationmaybe effect the activity of the-galactosidase to effect the germination of thebarnyard grass seeds.(5) The germination of lettuce seeds was effected by the light and temperature, inthe light or dark, when the temperature was up17oC, the germination of lettuce seedswas inhibited, and then send the lettuce seed in the optimum temperature, the lettuceseed can recover germinate, so the lettuce seeds had the typical thermoinhibitioncharacter.(6) Using5,10and20mM nitrate to treatment the lettuce seed, nitrate promotedthe germination of lettuce seeds. It broke the thermoinhition of lettuce seeds.(7) On the germination of the lettuce seed, the high temperature increased the ABAsynthesis genes expression of LsNCED1, LsNCED3and LsNCED4, and then decreasedthe ABA metabolism genes expression of LsABAox1, LsABAox2, LsABAox3andLsABAox4, added the10mM nitrate, nitrate decreased the expression of LsNCED3andLsNCED4, and then increased the expression of LsNCED1, LsABAox1, LsABAox2,LsABAox3and LsABAox4, especially about the expression of LsABAox1, LsABAox2andLsABAox3.(8) On the germination of the lettuce seed, the high temperature decreased the GAsynthesis genes expression of LsGA20ox1, LsGA20ox2and LsGA3ox1, and thenincreased the GA metabolism genes expression of LsGA2ox1and LsGA2ox2, added the10mM nitrate, nitrate increased the expression of LsGA20ox1, LsGA20ox2, LsGA3ox1and LsGA3ox2, and decreased the LsGA2ox2.