Plant Kingdom

Why This Chapter Matters

Plant Kingdom has 4-8 marks in NEET. Classification of plants (algae, bryophytes, pteridophytes, gymnosperms, angiosperms), alternation of generations, and key characteristics of each group are tested.

Core Concepts

1. Classification of Plant Kingdom

Thallophyta (Algae): No true stem, root, or leaves (thallus). No embryo.

Algae examples: Chlamydomonas (unicellular, green), Spirogyra (filamentous, green), Sargassum (brown, marine), Porphyra (red)

Algae pigments:

Green algae (Chlorophyceae): chlorophyll a, b | stored as starch

Brown algae (Phaeophyceae): chlorophyll a, c, fucoxanthin | stored as laminarin/mannitol

Red algae (Rhodophyceae): phycoerythrin, phycocyanin | stored as floridean starch

Bryophyta (Mosses, Liverworts):

Gametophyte dominant (haploid). Sporophyte dependent on gametophyte.

No true vascular tissue. No roots (rhizoids instead).

Examples: Marchantia (liverwort), Funaria (moss), Sphagnum (peat moss)

Archegonium (female) and Antheridium (male) sex organs.

Water required for fertilisation.

Pteridophyta (Ferns):

First true vascular plants (xylem + phloem). Sporophyte dominant (diploid).

No seeds. Reproduce by spores.

Examples: Selaginella, Salvinia, Pteris, Adiantum, Equisetum (horsetail)

Homosporous (one type of spore) — most ferns

Heterosporous (two types) — Selaginella, Salvinia

Gymnosperms:

Naked seeds (seeds not enclosed in fruit). No flowers.

Sporophyte dominant. Heterosporous (microsporangia + megasporangia).

Examples: Cycas, Pinus, Ginkgo, Welwitschia, Ephedra, Gnetum

Cycas: compound leaves; male and female cones on separate plants (dioecious)

Pinus: resin canals; male cone (microsporangiate strobili), female cone (megasporangiate)

Angiosperms:

Seeds enclosed in fruits. Flowers present. Most advanced.

Double fertilisation (unique to angiosperms).

Divided into Monocots and Dicots.

Feature	Monocot	Dicot

|---|---|---|

Cotyledons	1	2
Venation	Parallel	Reticulate
Floral parts	3 or multiples	4 or 5 or multiples
Root system	Fibrous	Tap root
Examples	Grass, wheat, rice, maize, lily	Pea, bean, mango, sunflower

2. Alternation of Generations

Gametophyte (n, haploid) → produces gametes → fertilisation → Zygote (2n)

Zygote → Sporophyte (2n, diploid) → meiosis → spores (n)

Spores → Gametophyte

Dominant generation:

Algae: Gametophyte dominant OR equal (depends on genus)

Bryophytes: Gametophyte dominant

Pteridophytes: Sporophyte dominant

Gymnosperms/Angiosperms: Sporophyte highly dominant (gametophyte is just a few cells)

3. Economic Importance

Algae:

•Agar-agar from Gelidium and Gracilaria (used in food and microbiology)

•Chlorella: single-cell protein

•Diatomite from diatoms (used in polishing, filtration)

•Sargassum: alginic acid production

Bryophytes:

•Sphagnum: fuel (peat), packing material, antiseptic

Pteridophytes:

•Azolla: bio-fertiliser (nitrogen fixation by symbiotic Anabaena)

•Salvinia: water pollution control

Gymnosperms:

•Pinus: turpentine, resin, timber

•Cycas: sago

•Ephedra: ephedrine (medicine)

PYQs (NEET)

NEET 2023: Which group of plants shows heterospory?

Selaginella and Salvinia (pteridophytes). Also all gymnosperms and angiosperms are heterosporous.

NEET 2022: Alternation of generations where sporophyte is dependent on gametophyte:

Bryophytes — the sporophyte grows on the gametophyte and is dependent on it for nutrition.

NEET 2021: Agar-agar is obtained from:

Red algae — specifically Gelidium and Gracilaria.

NEET 2020: In gymnosperms, seeds are:

Naked (not enclosed in fruit/ovary wall) — that is why they are called gymnosperms ("gymnos" = naked).

MCQ Practice

Q1. Dominant phase in bryophytes is:

(A) Sporophyte (B) Gametophyte ✓ (C) Both equal (D) Varies by species

Q2. First land plants with vascular tissue:

(A) Bryophytes (B) Pteridophytes ✓ (C) Gymnosperms (D) Algae

Q3. Double fertilisation is found in:

(A) Gymnosperms (B) Pteridophytes (C) Angiosperms ✓ (D) Bryophytes

Q4 (Hard). In which algae is the stored food laminarin?

(A) Green algae (B) Red algae (C) Brown algae ✓ (D) Blue-green algae

Revision Notes

CLASSIFICATION:
Algae: no true tissues, no embryo | Green/Brown/Red (different pigments)
Bryophytes: gametophyte dominant, no vascular tissue, rhizoids (not roots)
Pteridophytes: FIRST vascular plants, sporophyte dominant, no seeds
Gymnosperms: naked seeds, heterosporous, no fruit
Angiosperms: seeds in fruit, flowers, most advanced, double fertilisation

STORED FOOD:
Green algae: starch | Brown: laminarin/mannitol | Red: floridean starch

ALTERNATION OF GENERATIONS:
Bryophyte: Gametophyte (dominant) → Sporophyte (dependent)
Pteridophyte: Sporophyte dominant
Gymno/Angio: Sporophyte highly dominant

MONOCOT vs DICOT:
Monocot: 1 cotyledon, parallel venation, 3n floral parts, fibrous roots
Dicot: 2 cotyledons, reticulate venation, 4-5n floral parts, taproot