Fertilization and morphological development of Thai neem (Azadirachta indica A. Juss var. siamensis Valeton) fruit and seed
1997
Janjarat Chadarattanathiti
Present study was aimed in investigating the reproductive system and the morphological development of Thai neem (Azadirachta indica A. Juss var. siamensis Valeton) fruit and seed under the natural condition. With the fluorescence techniques, the pollen tube germinated after 4 hours of artificial pollination and the tube elongated up to the 50 percent of the length of conducting pore after 10-12 hours of artificial pollination. The tube penetrated the ovule through the chalazal end after 20-24 hours. The fertilization of Thai neem will thus take place after 24 hours of pollination. With plant micro techniques, the development of fruit and seed of Thai neem was carried out after artificial pollination for 7, 14, 21, 28, 35, 42, 49, 56 and 63 days. Physiological maturity was observed on 56 days after artificial pollination when the fruit size was fully developed (width 1.18 cm, length 1.5 cm). The study showed that after 7 days of artificial pollination, nuclear endosperm was observed. The globular shaped embryo surrounded by nuclear endosperm was detected after 14 days. On the third week, nuclear endosperm was changed to be cellular endosperm and heart shaped embryo was clearly observed. Embryo continued to develop further by using food support from endosperm. On 49th days after artificial pollination, endosperm was fully utilized and food was reserved in cotyledon in stead. As regards the thickness of seed coat, the thickness was 0.065 mm. On the 7th after artificial pollination and consisting of outer and inner integument. More layers of integument was observed in later stages. On the 35th days, maximum thickness of seed coat was found and at this stage there were 10 layers of outer integument and 2 layers of inner integument. Thickness of seed coat was decreased toward seed maturity when the thickness was only 0.059 mm.
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