【Objective】 The study aimed to investigate the dynamic changes in hormones and physiological metabolism indicators such as carbohydrates and flavonoids to provide a reference for the directional cultivation, pollination and gender identification of male and female Ginkgo biloba trees. 【Method】 Short fruit buds and leaves were collected from ginkgo trees during three developmental phases, that is, late flower bud differentiation (November 25 of previous year to March 16 of next year), flowering (March 17 to April 7), and after flowering (April 8 to April 28) to analyze the changes in the levels of hormones, carbohydrates, soluble proteins, total flavonoids, lactones, and peroxidase (POD) as well as phenylalanine ammonia-lyase (PAL) enzyme activities in female and male ginkgo trees. 【Result】 During the late flower bud differentiation stage, male trees had higher soluble sugar and protein contents and PAL activity than female trees, whereas during the flowering period, female trees had comparatively higher concentrations of soluble sugar, starch, soluble protein and PAL activity. However, gibberellin (GA) and zeatin (ZT) levels were significantly higher in the male trees during the flowering period. The considerably higher POD activity was observed in the female and male trees during the late flower bud differentiation period than during the other two periods, while the higher levels of ZT, GA, flavonoids and terpene lactones were observed during the flowering period. 【Conclusion】 Male and female ginkgo trees exhibited unsynchronized physiological metabolisms at the flowering time, and the peaks of soluble sugar, soluble protein, flavonoid and terpenoid lactone levels in male trees were observed approximately two weeks earlier than those in the female trees. High levels of GA, ZT, flavonoids and terpene lactones may be necessary for flowering and ovule development in male and female ginkgo trees, respectively.
【Objective】 In this study, high-embryogenic competence endosperm explants in Ginkgo biloba were screened out by investigating the relationship between the physiological changes in endosperm during different development periods and embryogenic callus induction. The results will provide supports for studying somatic embryogenesis and establishing a somatic embryogenesis system for G. biloba. 【Method】 Changes in antioxidant enzyme activities, flavonoids, and endogenous hormone content were measured, and embryogenic callus were induced using G. biloba endosperm as explants in eight stages (during June 10 to September 15). 【Result】 The endosperm development and embryogenic competence of G. biloba can be divided into three stages (Ⅰ-Ⅲ). The soluble protein and flavonoids content, peroxidase and catalaseenzyme activities, and indoleacetic acid (IAA) /abscisic acid (ABA) ratio in the endosperm of G. biloba all reached the highest levels; however, the (zeatin nucleoside (ZR) + isopentenyl pyrophosphate (iPA))/ABA ratio was lower than that at stage Ⅰ (during June 10 to June 30). Accordingly, the endosperm at this stage had high embryogenic competence and induction ability of embryogenic callus. Moreover, the endosperm had a high water content and superoxide dismutase (SOD) activity, and high IAA/ABA ratios, and it was also easy to induce callus; however, these induced callus were susceptible to loosening and easy browning, and the non-embryonic and embryogenic competence levels were lower at this stage. Stage Ⅱ lasted from June 30 to August 10. The three resistant enzyme activities, flavonoid content, and IAA/ABA ratios all exhibited low levels, while the (ZR+iPA)/ABA ratio was high. The callus induction rate was the lowest among the three stages, and the embryogenic competence level was lower than that at stage Ⅲ. 【Conclusion】 The embryogenic competence of G. biloba endosperm and embryogenic callus induction in the three stages of endosperm development was in the order stage Ⅲ > Ⅱ > Ⅰ. The optimum period of embryogenic competence in the endosperm explant was stage Ⅲ (August 17 to September 15) and the endosperm induced a high rate of embryogenic callus at this stage.
【Objective】 The annual variations and the correlation between the photosynthetic properties and flavonoids content in the leaves of female, male and golden-leaf (varieties of bud mutation) Ginkgo biloba were investigated to provide a references for the selection and breeding of robust G. biloba species, promotion of new varieties, and cultivation seedlings for harvesting leaves. 【Method】 Changes in photosynthetic pigments, chlorophyll fluorescence parameters, and flavonoid composition and content from April to November were studied in the leaves of female, male and grafted golden-leaf G. biloba trees. 【Result】 During the entire year, the water content in male trees was lower than that in female and golden-leaf trees in three G. biloba species, especially during the high-temperature summer period from June to September. Although the water content, relative leaf area and chlorophyll content in the male and golden-leaf G. biloba trees were lower than those in female trees, especially from May to August, their relative leaf area increased faster than the female trees. Furthermore, although the photochemical quenching (qP) and non-photochemical quenching (NPQ) coefficients were higher in the female trees than those in the male or golden-leaf tree, the maximum photochemical efficiency (Fv'/Fm') was lower in the female trees than that in the male and gold leaf tree. The annual variations in three flavonoid glycosides such as quercetin and total flavonoid contents in three G. biloba species revealed two high points, one in April to May and another in September. The highest level of the total flavonoid content in leaves was observed in September, and the total flavonoid content in the three tree species was in the following order: golden-leaf > male > female. The chlorophyll, carotene and quercetin contents in male trees were positively correlated with each other; however, a significant positive correlation between chlorophyll a, carotene, and total flavonoids was found in the female trees. The golden-leaf tree leaves maintained a golden yellow color from April to June owing to the lower chlorophyll content than their male and female counterparts during this period. However, their leaves changed from yellow to green after July, and their photosynthetic, flavonoid changes were closer to those of the male trees. Furthermore, the flavonoid content in golden-leaf trees was higher than that in the male and female trees. 【Conclusion】 The best harvesting stage for ginkgo leaves was in September in the Nanjing region of China; male and golden-leaf trees exhibited greater conduciveness to the cultivation of leaf-using forest; and the female trees exhibited higher stress resistance than male and golden-leaf trees. Golden-leaf G. biloba tree has an ornamental value and excellent economic characteristics, which makes it worth developing and utilizing vigorously in the future.
