During the second year of cone development in Pinus (pines), significant changes occur within the cone structure. These changes can be observed in the female cone, which is responsible for housing and producing seeds.
In the second year, the cone undergoes several important transformations. The cone scales, which protect the developing seeds, continue to enlarge and thicken. They become woody and develop a rough texture. The scales also become more closely packed together, providing further protection for the seeds.
At this stage, the ovules, which are the structures within the cone that eventually develop into seeds, continue their growth. They are attached to the cone scales by a stalk-like structure called the funiculus. The ovules mature and develop into seeds as they accumulate food reserves.
Additionally, the pollen grains produced by the male cones of other pine trees are carried by wind or other means to the female cone. If a pollen grain successfully reaches the ovule, it germinates and sends a pollen tube down the ovule's tissue. This allows the sperm cells to reach the egg cell, resulting in fertilization.
Overall, during the second year of cone development in Pinus, the cone scales mature and become protective structures, while the ovules develop into seeds. The fertilization process also takes place, enabling the formation of viable seeds within the cone.