Abstract:

Sorghum (Sorghum bicolor L. Moench) grows widely in the world as the fifth biggest crop in use for food, feed and raw material in brewing industry. Great achievements have been taken in routine breeding, and also in apomixis in sorghum. Reports on sorghum embryology mainly focused on the morphological structure and development of flower, megasporogenesis, microsporogensis, megagametophyte and so on. The objective of this study was to explore the fertiligation process of sorghum by routine paraffin-embedded section technique to offer some information for its genetic breeding, gene engineering and reproductive biology. The results showed that pollen grains germinated immediately when they fell on stigma in self-pollinated sorghum, then pollen tubes grew into the intercellular space of branched structure of penniform stigma, entering and penetrating ovary, and growing into micropyle. Pollen tube entered and destroyed one synergid and released successive round staff between egg and central cells. One sperm nucleus entered egg and the other entered central cell. Male and female nucleoli were fused at last. The performance time was as follows: pollen tube grew into micropyle and entered one synergid to release two sperms at 0.5–3 h after flowering; fusion of sperm-polar nucleus and egg-sperm nucleus took place at about 1–3 h after flowering; primary endosperm nucleus divided at about 4 h after flowering; zygote divided at 14 h after flowering; the dormancy stage of zygote was about 4–14 h after flowering, which is the proper time for transgenic operation with pollen-tube pathway technology and other physic-chemical mutagenesis.

Key words: Sorghum bicolor(L.) Moench, Pathway of pollen tube growth, Fertilization, Duration, Zygophase