2 The buds

If you look at a branch on a deciduous tree during the winter when the leaves are gone, you can see terminal buds at the very ends of the twigs. These are the points from which the next spring’s growth will take place. Buds are protected from freezing by a covering of moisture-conserving bud scales. Twigs also have side or lateral buds, from which side branches develop. Buds are formed in the summer and fall and remain dormant over winter. Dormancy is broken when suitable growing conditions return, usually in the spring.

If you look further back along a twig, you will come to a ring of thickened bark. This scar tissue marks the place where the terminal bud grew the previous year and is called the terminal bud scar. The distance between the scar and the new terminal bud is therefore the amount of growth that took place in one year. Knowing this, you can find the age of several branches of different sizes on a tree.

Buds are actually areas of growth; where the stem or branch lengthens or leaves develop. In vascular plants, most cells that have differentiated – into phloem or xylem for example – lose their ability to divide. Each cell of either xylem or phloem tissue is formed undifferentiated tissue that continues to divide by mitosis as long as the plant lives. This tissue, where ever it might be located in the plant, is referred to as meristem.

Meristematic tissue can be found at the tip of a stem. As a stem lengthens, the majority of the meristematic tissue remains at the tip and some remains behind. Branches and leaves develop from this remaining tissue. A bud actually forms before the end of the growth season and contains the differentiated cells (xylem, phloem, mesophyll and so on) of a leaf. These cells are quite small and in the new season, the leaves expand mostly from the enlargement of these small cells.

(1844 signs)

3 Photosynthesis

The leaves are the food factories of a tree. They contain chlorophyll, which facilitates photosynthesis and gives leaves their green color. Through a process called photosynthesis, leaves use the sun’s energy to convert carbon dioxide from the atmosphere and water from the soil into sugar and oxygen. The sugar, which is the tree’s food, is either used or stored in the branches, trunk and roots. The oxygen is released into the atmosphere.

The process of Photosynthesis (the process by which plants make sugar from sunlight, water, and carbon dioxide):

– sunlight shines through the top of the leaf and reaches the next layer of cells. The light energy is trapped by the chlorophyll in the chloroplasts. In the chloroplasts, a process that uses water changes the light energy into a kind of chemical energy. This chemical energy is stored in the chloroplasts;

– the chloroplasts use the chemical energy to make food. Air enters the leaf through the stomata and moves into tiny spaces around the food-making cells in the leaf. Carbon dioxide from the air passes through the cell walls and membranes of the cells. Carbon dioxide enters the chloroplasts where the previously stored chemical energy converts the carbon dioxide into sugar;

– tubes in the plant carry sugar from the leaf cells to other parts of the plant, such as roots, stems, and fruits. Cells in these parts of the tree store some of the sugar.

(1408 signs)