If you only ate one meal a week, do you think you would grow as tall
as you would otherwise? How long could you last without water or
air? We all have basic requirements necessary to maintain a healthy
body. These include oxygen, water, carbohydrates, and other nutrients.
Plants are no different. They require these things as well, and
it is the job of the horticulturist to make sure that they get them.
|Figure 4.1 A plant cell consists of numerous specialized organelles.
Photosynthesis occurs within the chloroplast. Other organelles include
ribosomes, mitochondrion, smooth and rough endoplasmic reticulum,
and the nucleus, which contains the plant cell’s DNA.
We get our oxygen from the atmosphere. So do plants, but it
must first diffuse into the soil because they respire or “breathe”
with their roots. For this reason, there must be a balance of
air and water in the soil. Many plants die from overwatering
because they do not get enough oxygen. On the other hand, if
the plant does not receive enough water, it wilts and eventually
dies because it accesses nutrients from minerals dissolved in the
water and because water is necessary for photosynthesis.
We get carbohydrates from eating plants. Plants, however,
make their own carbohydrates with photosynthesis. Photosynthesis
runs on solar energy, which is used to combine carbon
dioxide and water into the sugar called glucose. It happens in
the green-pigmented chloroplasts
found in the parenchyma cells
of leaves (Figure 4.1).
The duration and intensity of sunshine; the quality of the soil;
and such environmental factors as temperature, annual rainfall,
humidity, and wind are all variables that affect plant growth. As
you may have noticed, not everyone requires the same amount of
food or water. Also, some of us actually like cold weather, whereas
others prefer the heat. The specific cultural requirements of a
plant in a vegetable garden are different from those of a plant in
the wildflower meadow, as are those that evolved in alpine versus
tropical versus desert environments. Cultural requirements for
sunshine, soil quality, water, and climate are described below.