Page 8 - Tài liệu Ebook cây cảnh Bonsai Basics

I 0 HOW TREES GROW

Aerial parts plant life. It is the leaves that absorb
These consist of the trunk and the carbon dioxide from the atmosphere, a
branch system. From the base of the phenomenon which itself results from
trunk to where the first branches grow is photosynthesis which takes place in sun-
known as the bole and the top of the tree, light. In darkness, particularly at night,
at the tip of the last branch, is the crown. the plant gives off the oxygen contained
The branch system consists of the in the carbon dioxide. The carbohy-
branches a nd their sub-divisions, the drates necessary for growth are manu-
most slender of which produce the factured from water taken from the soil.
leaves. In nature, the development of The shape of leaves varies from one
these elements is directly related to the species to another, but there is a funda-
physical environment, such as sunlight, mental difference between the leaves of
temperature and wind. T he art of bonsai pines and simila r trees and the leaves of
lies in limiting the growth of the tree, other trees. The former are generally
while artificially maintaining the natural evergreen (that is, the leaves do not fall
look of its trunk and branch system. This all at once in autumn - or indeed at any
is done by precise cutting, pruning and time of year), the latter are deciduous,
wiring techniques, which are described since the leaves drop from the trees in
in detail later in this book. autumn. But one should be careful of
such generalizations since there are
many exceptions to the rule.
Foliage It is desirable to distinguish the
Leaves form an essential part of the tree needles of the conifers from the leaves of
and are directly involved in the tree's other types of tree. Leaves are made up
growth processes. In fact, they make of a petiole or leafstalk by which they are
possible the trapping of the sun's energy attached to the stem and a veined blade
in the green chlorophyll they contain, a or lamina containing the cells which
process vital to the development of all carry out photosynthesis.

blade

Most leaves are deciduous. The leaf itself is com- 1. Pinnate leaf (false acacia) 2. Compound leaf
posed of the blade and the petiole, or stalk, which with three leaflets (laburnum) 3. Palmate leaf
links it to the branch. (horse chestnut) 4. Simple leaf (oak)