See , Pinus tree has pyramid like shape....in simple words... Elder branches are larger than younger branches, so its looks like a cone...this pattern is called excurrent habit....this is due to..apical dominance in plant, auxin produced in the apical meristem inhibits axillary buds near the apical meristem from developing into actively growing shoots.. so this type of pattern developsso option Band the ..most.. important thing is that it helps in the..wind pollination.

Explanation:

Pinus is a genus of coniferous trees that exhibit excurrent habit, which means that the main stem continues to grow vertically and maintains its dominance over the lateral branches. This habit is mainly due to the presence of apical dominance.

Apical dominance:

Apical dominance is a phenomenon in plants that is characterized by the inhibition of the growth of lateral buds by the apical bud. The apical bud secretes hormones such as auxins that suppress the growth of lateral buds by inhibiting their elongation and cell division. This helps in maintaining the dominance of the main stem and the apical bud.

Role of apical dominance in Pinus:

In Pinus, the apical bud is the main growing point of the tree, and it maintains its dominance over the lateral branches by suppressing their growth. This results in the excurrent habit of Pinus trees, where the main stem grows vertically and maintains its dominance over the lateral branches.

Other factors:

Although apical dominance is the main factor that contributes to the excurrent habit in Pinus, other factors such as the presence of cytokinins and gibberellins can also affect the growth pattern of the tree. Cytokinins promote cell division and lateral bud growth, whereas gibberellins promote stem elongation. However, the effect of these hormones is overpowered by the dominance of the apical bud in Pinus trees.

Conclusion:

In conclusion, the excurrent habit in Pinus is mainly due to the presence of apical dominance, where the main stem maintains its dominance over the lateral branches by suppressing their growth. This results in the vertical growth pattern of Pinus trees. Other factors such as cytokinins and gibberellins may also play a role, but their effect is overpowered by the dominance of the apical bud.