Practice question

Androgenesis is commonly accomplished through culture of anthers or isolated microspores pollen at uninucleate stage, landmark discovery by Guha and Maheshwari 1964 in Datura innoxia demonstrating that anthers could produce haploid embryos on MS medium. Most responsive microspores are at mid uninucleate to early binucleate stage where gametophytic commitment is still reversible; vacuolate microspores have large central vacuole and peripheral nucleus poised for embryogenic switch. Anthers excised from surface sterilized buds given cold pretreatment 4 degrees for several days or heat shock 33 degrees that disrupts cytoskeleton and blocks starch accumulation are placed on agar solidified medium containing auxin 2,4-D and cytokinin BAP at low levels plus sucrose 3 percent often with activated charcoal adsorbing inhibitory phenolics from anther wall. Inside locule microspores undergo sporophytic divisions forming multicellular structures that rupture exine to emerge as globular embryos. Isolated microspore culture eliminates anther wall somatic tissue producing higher haploid yield and better for transformation but requires precise density control 10^4 per ml and nurse culture. Ovule culture corresponds to gynogenesis not androgenesis.