In this article we will discuss about the transverse sections of petiole of some flowers:- 1. Cucurbita 2. Sunflower 3. Piper Betle 4. Waterlily. 1. Cucurbita: A transverse section through the petiole of Cucurbita shows the following anatomical features (Fig. 5.124): It is wavy in outline having distinct ridges and furrows and a large cavity at the centre. (i) Epidermis: [...]
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 [...]