Table 2 Temperature Comparison between Cool Season and Warm Season Vegetables

3. Relative humidity: Moisture is defined as the ratio of water vapour in the air to the amount of water in the air. It is a very important factor in growth of plants. The relative humidity in the air is used by the plants and is very crucial for the transpiration of the plants. Transpiration is highest during hot, dry and windy days while transpiration slows down during cool and humid days. Water moves from areas of high relative humidity to areas of lower relative humidity.  Inside a leaf, the relative humidity between cells approaches 100%.  When the stomata opens, water vapors inside the leaf rush out forming a bubble of higher humidity around the stomata on the outside of the leaf and carbon dioxide move into the leaf through the stomata as shown in Figure 3. The difference in relative humidity around the stomata and adjacent air regulates transpiration rates and pulls water up through the xylem tissues.  When the supply of water from the roots is inadequate, the stomata closes, photosynthesis shuts down, and plants can wilt.