The Effect Of Exogenous AgNO₃ On Sex Differentiation In Bitter Gourd

As a monoecious annual plant, bitter gourd is rich in nutrient composition and medical value. Because the sex differentiation of bitter gourd is related to its yield and quality, it can broaden the category of exploring on the mechanism of sex determination in plants and it is beneficial to guide the breeding and production by studying the sex differentiation of bitter gourd. In this study, we took the female line ’44’ and monoecious inbred line ’18-2’ of bitter gourd as materials and determined the ethylene production and the contents of endogenous IAA, GA3, ABA and ZT in the female flowers produced under natural conditions respectively. By taking the female line ’44’ of Bitter gourd as material,we sprayed the AgNO₃ solution with a concentration of 250 mg·L-1 on the whole plant at the beginning of flowering and then we observed the development of the stamens induced by AgNO₃ treatment by means of paraffin section. In addition,we detected the ethylene production in the stem apex s and flower buds respectively during the formation of the bisexual flowers by gas chromatograph. At the same time, we determined the contents of endogenous IAA, GA3, ABA and ZT in the stem apexs and flower buds by enzyme linked immunosorbent assay and discussed the effect of AgNO₃ treatment on the sex differentiation of bitter gourd and its relationship with endogenous hormones. Through the determination of pollen viability, germination in vitro and pollination experiment, we verified the function of the bisexual flowers induced. The main results obtained were as follows:1. The IAA and GA3 content of gynoecious bitter gourd in plant stem tip was significantly higher than that of monoecious inbred lines.And the GA3,ZT and ABA content of gynoecious bitter gourd in female flowers bud was significantly higher than that of monoecious inbred lines.2. The application of exogenous AgNO₃ can induce the gynoecious bitter gourd produce bisexual flowers,but the bisexual flower buds have a quite different in appearancefrom the contrast,its bud length,weight and the diameter of the ovarywere significantly greater than the female flowers. The paraffin section observation showed that the stamens of normal female flowers had not completely disappeared. After AgNO₃ treatment of 9d,the stamens in the female flower significantly elongated, and after AgNO₃ treatment of 15 d,the bisexual flowers appeared.The bisexual flower period lasted about one week and then the stamens degenerated gradually and after AgNO₃ treatment of 27 d, the female state of the female plants recoveryed.3. After AgNO₃ treatment, the ethylene release rate of the stem apexs of gynoecious bitter gourd was significantly higher than that of the contrasts in the first 3¹2d.And in the flower buds, the ethylene release rate was also significantly higher than that of the contrasts in the first 3⁹d. But on the 15 th day,the ethylene release rate in the bisexual flower buds that induced by AgNO₃ was significantly lower than that in the female flowers. Preliminary thought that, the ethylene release rate of the stem tip and the bud have a close relationship with the gender transition of female flower to bisexual flower.4. After AgNO₃ treatment, the content of endogenous IAA in the stem apexs of the female plant of Bitter gourd did not significantly changed, but the the content of IAA in the flower buds significantly decreased in the first 3¹2d and the length, diameter and weight of buds significantly decreased at the same time. When the content of IAA returned to the normal level, the buds became larger. This showed that high level of IAA was conducive to the development of pistils of bitter gourd.5. After AgNO₃ treatment, the content of GA3 in the stem apexs of the female plant of bitter gourd did not changed, this could be inferred that GA3 had nothing to do with the sex transition of bitter gourd.However, the content of GA3 in the flower buds significantly decreased indicating that GA3 could be the key factor for the differentiation of bisexual flowers.6. After AgNO₃ treatment, the content of endogenous ZT and ABA did not changed no matter in the stem apexs or the flower buds of the female plant of bitter gourd.And this could be inferred that ZT and ABA had nothing to do with the sex differentiation of bitter gourd.7. The results of the pollen viability test and pollen germination test of the bisexualflower showed that the AgNO₃ pollen had a normal life force and could sprout pollen tube.From the pollination results we could see that this pollen had the same pollination function with the pollen of normal male flowers. But the pistils of the bisexual flowers induced after AgNO₃ treatment were unable to make their ovaries inflated no matter by selfing or testcrossing, even by granting the pollen of normal male flowers on the monoecious plants.This showed that the pistils of the bisexual flowers induced after AgNO₃ treatment lost the normal function of receiving pollen to complete double fertilization.