Plant KingdomNEET Botany · Class 11 · NCERT Chapter 3

You can expect 3 to 5 questions from Plant Kingdom in NEET 2027. It is a medium-weightage chapter with consistent PYQ frequency. The most tested areas are the three algae divisions (pigments, stored food, examples), differences between plant groups (vascular tissue, dominant generation, seeds), gymnosperms (Cycas vs Pinus), heterospory in pteridophytes, and alternation of generations.

The three algal divisions are classified mainly by their photosynthetic pigments: Chlorophyceae (green algae) have chlorophyll a and b, giving them a green colour. Phaeophyceae (brown algae) have chlorophyll a and c plus fucoxanthin, giving them an olive-green to brown colour. Rhodophyceae (red algae) have chlorophyll a and d plus phycoerythrin, giving them a red colour. Their stored food and cell wall composition also differ: Chlorophyceae store starch and have a cellulose cell wall; Phaeophyceae store mannitol and laminarin with a cellulose plus algin cell wall; Rhodophyceae store floridean starch with a cellulose plus phycocolloid cell wall.

Bryophytes are called the amphibians of the plant kingdom because they can live on land but need water for fertilization. The male gametes (antherozoids) are flagellated and must swim through a film of water to reach the female archegonium. They have no vascular tissue and no true roots, stems, or leaves, so they cannot survive in dry conditions for long. This dependence on water for sexual reproduction, combined with their ability to live on land, makes them analogous to amphibians in the animal kingdom.

Pteridophytes are the first vascular land plants (they have xylem and phloem) but they do not produce seeds. They reproduce by spores and need water for fertilization. The sporophyte is dominant and the gametophyte is small and independent. Gymnosperms also have vascular tissue but they produce naked seeds (not enclosed in a fruit). They produce pollen grains, so they do not need water for fertilization. Examples of pteridophytes: Selaginella, Equisetum, Adiantum. Examples of gymnosperms: Cycas, Pinus, Gnetum.

Heterospory means the production of two morphologically different types of spores: microspores (small spores that give rise to the male gametophyte) and megaspores (large spores that give rise to the female gametophyte). Among pteridophytes, Selaginella (land) and Salvinia (aquatic) show heterospory. In seed plants, the megaspore is retained on the parent plant and fertilization and early embryo development occur there; this is the origin of seed habit. True seeds (with a seed coat, food reserve, and embryo) first appear in gymnosperms. Heterospory is therefore the evolutionary stepping stone to seed habit.

Alternation of generations is the alternation between a haploid (n) gametophyte phase and a diploid (2n) sporophyte phase in the life cycle of a plant. Three patterns exist: (1) Haplontic: gametophyte is dominant and long-lived; sporophyte is reduced and short-lived (just the zygote). Most algae follow this. (2) Diplontic: sporophyte is dominant; gametophyte is reduced to just a few cells. All seed plants (gymnosperms and angiosperms) follow this. Fucus (brown alga) also shows diplontic alternation. (3) Haplo-diplontic: both generations are well-developed and free-living. Bryophytes and pteridophytes both fall here. In bryophytes the gametophyte is larger and dominant; in pteridophytes the sporophyte is larger and dominant.