Photosynthesis, Respiration, Transpiration and Photomorphogenesis – The Basics
The growth of a plant is significantly accelerated in a vineshelter compared to those grown without. This is because the vineshelter provides an ideal microclimate that is conducive to improved plant growth. The factors that contribute to the microclimate include warmth, levels of carbon dioxide and moisture, light spectrum and intensity. They intervene in the key processes of Photosynthesis, Respiration, Transpiration and Photomorphogenesis.
Photosynthesis is the process through which plants convert CO2 and water into oxygen and energy stored in the form of carbohydrates like sugar and starch. This process requires blue and red light which is absorbed by the green chlorophyll in the plant. Photosynthesis requires a good supply of CO2 and water. It also performs better at higher temperatures, provided that these temperatures do not become too hot (usually above 40 oC).
The stored carbohydrates now react with oxygen and produce CO2 and energy in a new chemical form. This newly produced energy is used for cell growth and building new tissues. The chemical process is called respiration. The plant controls its respiration process in accordance to its climatic environment. Heat and moisture in the air around the plant have therefore a profound effect on the plant growth. It is important that the levels of respiration and photosynthesis are in balance.
Transpiration is the evaporation of water from the aerial parts of the plants. It is basically the “engine” responsible for the mass flow of water trough the plant. Transpiration is responsible for several things:
- Transporting minerals from the soil throughout the plant.
- Cooling the plant through evaporation.
- Moving sugars and plant chemicals.
- Maintaining turgor pressure.
Transpiration uses about 90 percent of the water that enters a plant's roots. The other 10 percent is used in chemical reactions and in plant tissues.
Photomorphogenesis refers to an independent process whereby specific wavelengths of light direct the growth and morphology of the plant – its shape, node to node distance, root to shoot ratio, flowering, shade avoidance, etc. In particular, the ratio (R:F-R) between the narrow bands of Red and Far Red lights will affect the growth of the plant, and in particular the process of elongation. These lights sensitive pigments are also located within the leaf and are called phytochromes. It is important that the ratio of these lights is not significantly distorted away from their natural daylight ratio of 1:1.