Question

write three points of differences in pollen grains of Ephedra and Gnetum​

Answer 1

Answer:

Ephedra pollen is large, between 34 and 81 µm in its longest (equatorial) diameter, and, as in remaining Gnetales, the pollen wall consists of a homogenous tectum, a gran- ular infratectum of varying density. A thin foot layer adnate to a distinct lamellar endexine.

The pollen grains of Gnetum are subspheroidal or irregular-apolar, inperturate, 11.21–22.44 µm in the long axis and 9.34–20.47 µm in the short axis. The axin surface is covered with spinules, averaging 1.12 (0.81–1.46) µm apart over 0.50 (0.30–0.71) µm long distances. The exine is approximately 0.55 µm thick and contains ectexin and andexin. Actexin consists of a thin tectum and an infratectal granular layer. The tectum protrudes outwards, forming spinules. Andexins are composed of discontinuous lamellae, with lacunae between the lamellae.