Q.Number of cotyledons in pinus sead are:

General Characteristics of Gymnosperms

Imagine a pine tree. You see cones hanging from its branches — some woody and hard, some softer. Inside those cones, seeds sit exposed on the surface of scales, not hidden inside a fruit. That is the single most important idea: naked seeds. The word "gymnosperm" itself comes from Greek — gymnos (naked) + sperma (seed). Unlike flowering plants (angiosperms), gymnosperms never enclose their ovules inside an ovary. The ovule sits directly on the surface of a sporophyll (a leaf that bears spores) or a cone scale.

The Sporophyte is the Dominant Plant

What you see when you look at a pine, a cycad, or a Ginkgo tree is the sporophyte — the diploid, spore-producing generation. It is a well-differentiated plant body with true roots, stems, and leaves. The sporophyte is perennial, long-lived, and often massive. In contrast, the gametophyte (the haploid, gamete-producing generation) is tiny and completely dependent on the sporophyte. This is the opposite of what you see in bryophytes (mosses), where the gametophyte is the main plant.

Roots, Stems, and Leaves

The roots are generally taproots. In many gymnosperms (especially Cycas), special roots called coralloid roots develop. These are short, branched, coral-like structures that live in association with nitrogen-fixing cyanobacteria — a built-in fertiliser factory.

The stem is usually woody and branched (except in Cycas, which has an unbranched trunk). The wood is made of tracheids (long, tapered cells that conduct water) but lacks the vessels found in most flowering plants. This is a primitive feature. The wood also contains rays for lateral transport.

Leaves vary widely. In Cycas, leaves are large, pinnately compound (like a fern frond). In Pinus, leaves are needle-like, clustered in bundles called fascicles — an adaptation to reduce water loss. In Ginkgo, leaves are fan-shaped with a distinct notch. All gymnosperm leaves have a thick cuticle and sunken stomata to conserve water.

Cones and Reproduction

Gymnosperms are heterosporous — they produce two kinds of spores: microspores (male) and megaspores (female). These spores are borne on specialised leaves called sporophylls, which are arranged in compact structures called cones or strobili.

• Male cones (microsporangiate strobili) are small, soft, and short-lived. They produce microspores that develop into pollen grains.
• Female cones (megasporangiate strobili) are larger, woody, and long-lived. They bear ovules on the surface of scales. Each ovule contains a megaspore mother cell that gives rise to the female gametophyte.

Pollination is by wind (anemophily). The pollen grain lands directly on the ovule — there is no stigma or style. The pollen tube delivers sperm cells to the egg. In Cycas and Ginkgo, the sperm are flagellated and motile — a primitive trait shared with ferns. In Pinus and other conifers, sperm are non-motile.

After fertilisation, the zygote develops into an embryo inside the seed. The seed is naked — it is not enclosed in a fruit. It consists of the embryo, a food reserve (female gametophyte tissue), and a seed coat derived from the integument of the ovule.

Key Examples