In this article we will discuss about the composition and importance of exince in pollen and spore walls. Composition of Exine: Exine is mainly composed of sporopollenin. Apart from sporopollenin glycoproteins are present in the chambers formed by bacula in tectate pollen. It is important in pollen-stigma interaction. The presence of glycocalyces (sing, glycocalyx) is reported from exine. Glycocalyx forms [...]
In this article we will discuss about the size of pollen and spore walls. Size: There exist much variations in sizes of pollen and spores. The size may be 5 µ × 2.4 µ as observed in pollen of forget-me-not (Myosotis) or as high as 200 µ or more as is noted in certain genera of Cucurbitaceae and Nyctaginaceae etc. [...]
Polarity is defined as the condition of having distinct poles in a pollen grain. Jackson in 1928 assumed that a pollen grain points to the poles like Silphium. Silphium laciniatum, also known as compass plant, has leaves that 'turn their edges north and south and avoid the mid-day radiation' —Willis. Pollen mother cell after meiosis forms four pollen grains that [...]