Sunlight plays a major role in stimulating plants growth by providing the radiant energy to raise the temperature and humidity of soil and air. For most of the plants, sunshine and a consequent high temperature encourage maximum new growth, flowering and fruiting. A warm, sunny summer will result in greatly enhanced food storage to plants and helps to firm their protective tissue, which means that better propagating material is produced and that the plants will be more resistant to the winter cold.
Daylength
The duration of daylight in a 24 hours period will vary by latitude and season. It affects flowering and fruiting of some plants which need a specific amount of daylight in a 24 hours period. According to their need of daylight, plants can be categorized as short day and long day plants. The short day plants will need less than 12 hours of daylight, while the long day plants will need more than 12 hours of daylight.
Using artificial lightning or blacking out the natural light, we can manipulate in our advantage, it necessary, the flowering time of plants that are daylength-sensitive. Germination of seeds and seedlings development may be advanced by the same method.
How plants respond to sunlight
As a natural habit, plants will always grow towards the direction of the sunlight and will develop more shots or foliage on the side that is towards the sunlight. Plants that are subjected to a poor or localized light source will become drawn or etiolated as they are trying to reach more light. The intensity of sunlight wide dictate the flower opening in some plants.
Sun or shade
To achieve the optimum growth, most leafy plants will require the maximum amount of light they can get. Some garden plants thrive in direct, strong sunshine, while others will not tolerate it and will need a place in the shade. Half-hardy plants, most fruits and vegetables, roses and plants originated from Mediterranean area will all thrive best in full sun. Many rhododendrons prefer to have some shade. Ivies and periwinkles will do best in heavily shaded areas.
Excessive sunshine
Strong sunlight may scorch the flowers and leaves of plants if they have been recently watered. In occasional situations it can cause the splitting of fruits or bark. To prevent such problems you must chose the appropriate planting site according to plants necessities. For vulnerable plants you must provide artificial shade in summer and most especially for the plants in greenhouses and frames.
