Pg. 5-7 Ovule Structure, Pollen Viability and Pollen Tube Growth in Litchi chinensis Sonn. c./ HLH Mauritius

In this paper the authors report on in vitro as well as in vivo pollen germination, pollen tube growth and the structure of the ovule and aril. For in vitro germination studies, the best results we obtained at 25° C in a medium containing 20 percent sucrose. In vivo pollen tube growth was slightly better at 25 °C and 30 ° C than at 20 °C. Evidence confirming the hypothesis that the obturator acts as a guide for pollen tubes on their way towards the micropyle, is presented.

Summary:

• The study investigates the ovule structure, pollen viability, and pollen tube growth in Litchi chinensis Sonn. cv. HLH Mauritius.
• In vitro pollen germination was best at 25°C in a medium with 20% sucrose, with pollen tubes reaching maximum length after 24 hours.
• In vivo pollen tube growth was slightly better at 25°C and 30°C compared to 20°C.
• Evidence is presented confirming that the obturator acts as a guide for pollen tubes towards the micropyle.
• Litchi flowers exhibit three phases: male phase, female phase, and a second male phase, with flowers being functionally monoecious.
• The pistil consists of a bilobed ovary, a basal style, and a bifid stigma with receptive stigma lobes during pollination.
• Pollen tubes grow along the surface of the obturator papillae towards the micropyle, supporting the role of the aril as an obturator.
• The study finds that pollen tube performance varies with temperature and sugar concentration in the medium.
• The aril and obturator are considered the same structure performing different functions, with the aril developing further after fertilization.
• The research highlights challenges in litchi production including fruit drop related to pollination and fertilization failures.
• Technical methodologies include use of light microscopy with epifluorescence optics and histological techniques for ovule study.
• The study is supported by the South African Litchi Growers Association and conducted at the University of Pretoria.