POINTS OF GROWTH IN PLANTS

Plant growth varies. Different species of plants grow differently. Some species grow into short plants with soft stems which live for only a few weeks or a few months while some other species grow tall and large, have wooden trunks, and live for years.

What part of plants controls their growth? How do plants become longer? Observe the stem of a plant in Figure 1. On the stem you see two types of buds. At the tip there is a terminal bud, which is also known as an apical meristem. It determines the increase of plant length. Along the stem there are lateral buds, which are also known as side buds, or axillary buds. They can finally grow into branches, leaves, or flowers. Buds are the start of new growth and the points where they appear are nodes of growth.
Some plant species have stems that keep becoming larger. In fact, some large stems like those found in banyan trees, teak trees, and some other trees are even 1 to 2 meters in diameter. Stem enlargement is determined by the presence of cambium; it is located between the xylem and phloem and its function is forming new xylem and phloem . See Picture 2.
In Picture 1 you can see that the diameter of the lower part of the stem is larger than its upper part. It is because the quantity of xylem and phloem increases in the same direction. It means that new xylem and phloem are continuously being produced. They are produced by the cambium.

Questions:
1.Which tree lives longer, the one with soft stem or the one with wooden trunk?
2.Is this statement true or false? “The lateral bud makes the stem grow higher”.
3.What is the function of the cambium?
4.Why does the lower part of the stem become larger than the upper part?