Module twelve discusses plant development regulation through controlling temperature variations as well as different conditioning affects.
By controlling internode length and height, the greenhouse manager can control the ultimate length of the crop. This helps with the transplant process of varying plant types, whether they’re floral or vegetative, which is a primary purpose of many greenhouses. Temperature is a major factor in trying to determine the quantity of nodes that will develop and the rate of the node development on each crop. The measurement of node formation is known as leaf unfolding, this shows which temperatures of optimal. If the temperatures are too low then the plant reduces in number of nodes, and if the temperatures are too high the plant may cease all development. ADT, average daily temperature, determines internode length and effects the DIF, or temperature control, technique. This is highly determined by the genetics of the plant species itself.
Biological and environmental control are typically the two primary sources a grower observes. Shortened growing plants are a greenhouse managers first option when trying to control height, yet this is all dependent on the crop species and the environmental conditions they require. Cultivating control can be the manipulation of container size, scheduled timing, fertilizer or nutrition management, light quality and quantity, pinching, temperature variations, or irrigation practice. Container size, if minimized, can cause root restriction thus controlling plant growth and nutrient intake. Irrigation practices includes withholding watering and inducing drought stress by allowing plants to slightly wilt in between irrigation periods. Nutrients can be managed by withholding and reducing fertilizer quantity, which essentially is the reduction of nitrogen content.
Another aspect going into greenhouse management is conditioning the crops to be drought resistant while still optimizing growth. As mentioned earlier, height is relative in order to create uniform products and minimize issues when transplanting crops. Uniformity is vital especially when considering vegetable crops. Chemical growth regulation during the process of transplanting crops, is something to consider which is why temperature control is the most effective growth method. Other more organic methods of controlling transplant height uniformity include manipulating fertilizer contents or reducing irrigation. These methods help to strengthen the crop’s stress tolerance when undergoing the transplant. MSC, or moisture strength conditioning, is the irrigation control method that exposes the plant to non-detrimental water deficiencies. There is also the technique of brushing which is just climate and height control within the plant.
On a small scale, brushing was effective in the moderation of height control. There was little to no damage within the leaf structures and no detrimental effect on quantity. Yet there was a large reduction in plant development when undergoing the process of transplanting. Overall brushing is a good non-chemical method in optimizing uniformity but did little to increase stress and drought resistance. MSC had a similar end result as brushing, since it reduced plant development to create uniformity within transplanting crops. Maintaining stress and drought resistance was the only complication since it is difficult to achieve when using nonchemical growth regulating methods.
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