Pg. 9-12 Studies on the Morphology, Viability and Storage of Pollen Grains of Litchi (Litchi Chinensis Sonn)

A study was made of litchi pollen grains using the scanning electron microscope. Germination tests were carried out on pollen, from M₁ and M₂ flowers of several cultivars, stored at various low temperatures or in a series of organic solvents. It appears that pollen from M₂ flowers has greater tolerance to stress conditions.

Summary:

• The study examined litchi (Litchi chinensis Sonn) pollen grains using scanning electron microscopy (SEM) and conducted germination tests on pollen from male flower phases M₁ and M₂ of different cultivars.
• Litchi pollen grains are isopolar, radially symmetrical, tricolporate, and spherical when hydrated, with striate-reticulate ornamentation and opercula covering the pores.
• There were no major morphological differences between pollen from different cultivars or between M₁ and M₂ pollen, except for some differences in grain size.
• Both M₁ and M₂ pollen contained starch and proteins, detected by specific staining, which may relate to pollen viability and longevity.
• A high percentage of aborted pollen grains were observed in microsporangia across cultivars.
• Viability tests showed M₂ pollen generally had higher germination rates (~40%) and greater tolerance to stress conditions, including storage at low temperatures (4°C, 0°C, liquid nitrogen) and in organic solvents, compared to M₁ pollen.
• Storage in non-polar solvents like xylene and N-butyl alcohol preserved viability better than polar solvents like chloroform and acetone, which were detrimental likely due to damage to pollen membrane lipids.
• The study suggests M₂ pollen is more viable and likely more important for pollination, fruit-set, and yield in litchi cultivation.
• Differences in pollen viability may be influenced by environmental stresses during flower development.
• The findings offer detailed new insights into litchi pollen morphology at the electron microscopic level and have implications for improving litchi fruit production through better pollen management.