Studies On Seed Dormancy Mechanisms And Dormancy Breaking Methods Of Sagittaria Trifolia L

Sagittaria Trifolia Linn, one of the varieties of Arrowhead, is the common perennial herbaceous plants to be found in paddy fields. In recent years, this weed has become the main primary malignant weeds in the paddy fields all over the country. Seeds of Sagittaria Trifolia Linn were found to have an character of dormancy, which made it impossible to complete the bioassay taking Sagittaria Trifolia as the object. The causes of seed dormancy of Sagittaria Trifolia Linn were discussed, by measuring the testa permeability, each part of the seed extract liquid organic solvent extraction and biometrics to find out the method for breaking seed dormancy. In order to find the most quickly method to break the dormancy of Sagittaria Trifolia seeds, we breaked Sagittaria Trifolia seeds dormancy by mechanical, physical, chemical, plant hormone and stratification methods. The main results of this study were as follows:The latest seeds of Sagittaria Trifolia Linn had already got the complete structure,but because of the small volume, embryo rates were only30.75%～40.38%, so seeds of Sagittaria Trifolia Linn need the physiological after-ripening process to sprout; Lactea are compact, cells arranged closely, permeability was poor, moreover,there exists germination inhibitors in testa and embryo, all of these characteristics lead to the dormancy of Sagittaria Trifolia Linn,that means Sagittaria Trifolia Linn possesses comprehensive dormancy characteristic.That is less effective to break Sagittaria Trifolia seeds dormancy by Mechanical and physical method. Among the chemicals, the best way the best way was by soaking NaOH solution, soaking in25%NaOH solution for4hours, the germination rate of Sagittaria trifolia reached73.00%. And Sagittaria trifolia seeds can partly break the dormancy by treating with KOH and HC1, and among all the treatment, the germination rate reached respectively the top to50.33%and48.33%by soaking the seeds. The highest germination rate of Sagittaria trifolia treated by soaking with HNO3, H2SO4, Na2CO3, NaHCO3, NaCl and KNO3in the experience only reached about10percent. The plant growth regulator, such as GA3, IAA,6-BA and BR could not effectively break the dormancy of Sagittaria trifolia seeds. The dormancy of Sagittaria trifolia seeds could not be overcome by temperature stratification. The seed dormancy could effectively overcome by low temperate and overwintering stratification, When we used the overwinter stratification treat the seed, it would take a long time to break the dormancy, and the low temperature stratification test showed first increased and then a steady state after45d (in pot experiments condition), the seed couldn’t break the dormancy before15d, and the germination rate will reach80%at30d, after45d the rate will be hold in86.67%.The effects of substances extracted by different organic solvents(methanol, diethyl ether, Petroleum ether, Ethyl acetate)from testa and embryo on seed germinations of carrot and cucumber were as follows:substances extracted by methanol had the most obvious inhibition to germinations, root growths and plant growths of carrot and cucumber. It showed that methanol is the best organic solvent for extracting substances from Sagittaria trifolia. Substances extracted by other organic solvents had no inhibition to germinations, root growths and plant growths of carrot and cucumber.Effects of substances extracted by different concentrations of methanol from Sagittaria trifolia before and after stratifcation treatments on seed germinations and plant growth of carrot and cucumber were as follows:substances extracted by methanol form testa and embryo before stratifcation treatment had obvious inhibition to germinations, root growths and plant growths of carrot and cucumber, and the function became greater when the concentration of methanol increased, also the effect of substance extracted from embryo was greater than substance from testa. Substances extracted by methanol form testa and embryo after stratifcation treatment had no inhibition to germinations, root growths and plant growths of carrot and cucumber. That indicated that there exists germinate inhibitions in seeds of Sagittaria trifolia, and stratifcation treatment can help to remove the inhibitions.