HOW PLANTS GROW - Pruning for Flowers and Fruit - page 6

only in leaves, but in green stems and unripe
fruit. These plant parts must be exposed to
light to photosynthesise and therefore
manufacture simple sugars.

Leavesandotherplantparts
What, you may ask, does a grey or even black
leaf do? How do cacti work, or 'air' plants
with no roots at all? One thing is certain, tear
any leaf or stem and you will find some
'green' inside. These are the green pigments
in the chloroplasts that manufacture food by
photosynthesis. Cacti have made their stems
into photosynthetic surfaces, while the
'leaves' are the spines. Air plants, such as
Spanish moss that hangs from trees in the
Deep South of the USA, get their water from
the humid atmosphere and their grey furry
leaf coating limits moisture loss. The variety
of plant physiology and adaptation to climate
is mind-blowing; however, all plants have in
common the ability to photosynthesise. The
only exceptions are plants that draw nutrients
and water from another plant by attaching
themselves to the other plant's roots or stems
- known as parasites.

Figure 1.8 View from the end of an apple stem. Each leaf
arranges itself so as not to shade the next.

apples and pears, the leaves are arranged in
groups of five spiralling around the stem (see
Figure 1.8).

When looked at 'end on' it is easy to see
that each leaf is exposed to the maximum
amount of sunlight while still not shading its
neighbour. There are five buds perfectly
angled until the next bud is placed directly
above or below the first bud, but at some
distance. Other plants have buds/leaves that
sit opposite each other on the stem
(see Figure 1.9).

The delivery of water, nutrients and sugars
through the plant follow prescribed paths.
Fortunately, the leaves and the buds they
spring from are produced in just such an
orderly and efficient way.

While this may all seem interesting but not
particularly relevant to pruning, consider
that each leaf shelters a bud from which a
stem may result. The leaf arrangement,
especially in many large woody plants,
dictates the placement of branches. It
empowers the pruner to choose which
direction the future branch will grow. This is

Leafarrangement
The arrangement of leaves/buds on a stem
are genetically predetermined in each species
of plant. It is called phyllotaxis , from the Greek
phyllon meaning 'leaf', and taxis meaning
'arrangement'. On many plants, such as