Question

Explain how the pine life cycle in Figure 30.4 reflects the five adaptations common to all seed plants.

Short answer

The pine tree has sporangia on scalelike structures clustered tightly in cones. Conifers, like other seed plants, are heterosporous. They have two different forms of sporangia that create two different types of spores.

Microsporangia and megasporangia. Small pollen cones and large ovulate cones produce two types of spores in conifers: small pollen cones and bigger ovulate cones.

Step-by-step solution

Gymnosperms tree or seed plants

Gymnosperms are seed-bearing plants that, unlike angiosperms, generate seeds rather than fruits. These plants generate a cone-like arrangement on the surface of leaves or at the end of stalks.

The ovules are not contained within the ovary wall in these plants. It remains visible after fertilization and before it develops into a seed, for example, conifers, pine, and more.

Pine plants and their characterization

The difference in structure between these two plants is due to nature's basic law of adaptation. It is a proven fact that all creatures, whether plants or animals, adapt to their environment.

Pine trees are tall, with thin leaves (also known as needles) that help to reduce water loss through transpiration.

Life cycle events of pine plants that have common adaptations to seed plants

In the pine life cycle, the megasporangium leads to the formation of female gametophyte found in the ovule, and the sporangium and integument cover it. Each gametophyte develops archegonia, which each comprises an egg cell.

Pollen is formed in the male cones' microsporangia.A generative nucleus, tube nucleus, and two body cells make up each pollen grain. Pollen is carried to the entrance of the ovule by air.

The sperm nucleus (produced from one division of the generative nucleus) is transferred to the ovule by a pollen tube formed by the tube cell. After the fertilization, an embryo grows in the ovule.

The integument (seed coat), nutritive tissue (gametophyte), and embryo combine to create a seed (next-generation plant or sporophyte).