Notes on Gymnosperms l The Plant Kingdom l NEET 2025 / 2026

 

Gymnosperms

• Definition: Gymnosperms (gymnos: naked, sperma: seeds) are plants with exposed ovules and seeds, not enclosed by an ovary wall.
• General Characteristics:
• Includes medium to tall trees and shrubs.
• Example: Giant redwood tree (Sequoia), one of the tallest tree species.
• Roots:
• Typically tap roots.
• Some have mycorrhizal associations (e.g., Pinus).
• Some possess coralloid roots with N2-fixing cyanobacteria (e.g., Cycas).
• Stems: Can be unbranched (e.g., Cycas) or branched (e.g., Pinus, Cedrus).
• Leaves:
• May be simple or compound.
• Pinnate leaves in Cycas persist for several years.
• Adaptations to withstand extreme conditions (temperature, humidity, wind) include needle-like leaves, thick cuticle, and sunken stomata to reduce water loss.

Reproduction in Gymnosperms

• Heterosporous: Produces both microspores and megaspores.
• Sporangia:
• Borne on sporophylls arranged in strobili (cones).
• Male Strobili: Microsporangiate, bearing microsporophylls and microsporangia.
• Microspores develop into pollen grains (male gametophyte).
• Female Strobili: Macrosporangiate, bearing megasporophylls with ovules.
• Megaspore mother cell in the nucellus undergoes meiosis to form megaspores.
• One megaspore develops into a female gametophyte with archegonia.

Fertilization and Seed Development

• Pollination:
• Pollen grains released from microsporangium are carried by air to the ovules.
• Pollen tube grows towards archegonia, discharging male gametes near the archegonia mouth.
• Post-fertilization:
• Zygote develops into an embryo.
• Ovules mature into uncovered seeds.

Distinctions from Bryophytes and Pteridophytes

• Gametophytes:
• Both male and female gametophytes remain within sporangia on sporophytes.
• Do not have an independent free-living existence.
• Seed Development:
• Seeds are naked, not enclosed by fruit or ovary wall.

Mind Map

Gymnosperms Overview

• Definition: Plants with naked seeds and exposed ovules.
• Examples: Sequoia, Pinus, Cycas.

Structure

• Roots:
• Tap roots.
• Mycorrhizal associations.
• Coralloid roots with cyanobacteria.
• Stems:
• Unbranched (Cycas) or branched (Pinus, Cedrus).
• Leaves:
• Simple or compound.
• Adaptations: Needle-like, thick cuticle, sunken stomata.

Reproduction

• Heterosporous: Microspores and megaspores.
• Male Strobili:
• Microsporangia with pollen grains (male gametophyte).
• Female Strobili:
• Megasporangia with ovules (female gametophyte).
• Megaspore mother cell → Megaspores → Female gametophyte with archegonia.

Pollination & Seed Development

• Pollination: Airborne pollen grains → Ovules.
• Fertilization:
• Pollen tube → Archegonia.
• Male gametes discharge.
• Post-fertilization:
• Zygote → Embryo.
• Ovules → Naked seeds.

Differences from Bryophytes & Pteridophytes

• Gametophytes: Dependent on sporophytes.
• Seeds: Naked, not enclosed

Also Read:

• Plant Kingdom - NOTES and MCQs
• Gymnosperms - MCQs