Mike Straumietis, Founder and CEO of Advanced Nutrients, notes that several environmental factors affect plants’ growth. These include nutrition, light, temperature, and water, to name a few. By understanding these factors, you may manipulate plants to meet their needs and your needs as a plant grower.
Below, Mike Straumietis discusses five factors affecting plant growth.
Light
Light has three characteristics that affect plants’ growth: quality, quantity, and duration.
The quality of light refers to the color or wavelength of light. Sunlight supplies the complete range of wavelengths — bands of red, orange, yellow, green, blue, indigo, and violet.
Plants absorb blue and red light. Therefore, these lights have the greatest effect on plant growth. Blue is responsible primarily for vegetative (leaf) growth, while red encourages flowering when combined with blue light. Fluorescent or cool white light is high in the blue wavelength. It promotes leafy growth and is ideal for starting seedlings. Incandescent light has a lot of red or orange lights. However, it generally produces too much heat to be a valuable light source for plants.
The quantity of light refers to the intensity or concentration of sunlight. The maximum amount of light can be harnessed during the summer, whereas the minimum amount is during the winter. The more light a plant receives from the sun, the greater its capacity for producing food via photosynthesis, but only up to a certain point.
Light quantity can be manipulated to get different plant growth patterns. To increase light, surround plants with reflective materials, white background, or supplemental lights. To decrease light, cover plants with cheesecloth or woven shade cloths.
The duration of light is also known as the photoperiod, or how much time a plant is exposed to light. Scientists and researchers used to think that the length of the photoperiod triggered flowering and other responses within plants. This is why they describe plants as short-day or long-day, and it depends on what conditions they flower under. However, Mike Straumietis notes that it is not the length of the photoperiod but rather the length of uninterrupted periods of darkness that is crucial to floral development.
As mentioned earlier, plants are classified into three types. There are short-day (long-night), long-day (short-night), or day-neutral. How they are classified depends on their response to the duration of light or darkness. Some plants don’t fit into any category; in fact, they respond to combinations of day lengths. A perfect example of this would be petunias, which bloom regardless of day length but will bloom earlier and more profusely with long days.
Flowering
There are times when horticulturists combine temperature with day length to manipulate flowering. Take, for instance, a Christmas cactus, which forms flowers due to a mix of short days and low temperatures. To facilitate the blooming of a Christmas cactus, you can put it in a room with over 12 hours of darkness every day and a temperature between 50° to 55°F until the flower buds form. Other plants, such as spinach, will flower when temperatures are high and days are long. However, if temperatures are too low, the fruit will not be set on warm-season crops like tomatoes.
Crop Quality
Cooler temperatures may reduce energy use and increase sugar storage. This leaves crops such as ripe winter squash on the vine during cool fall nights, increasing their sweetness. Adverse temperatures, meanwhile, cause stunted growth and low-quality vegetables. Bitter lettuce, for example, happens when lettuce is placed in high temperatures.
Temperature
Temperature influences most plant processes, including respiration, photosynthesis, transpiration, germination, flowering, and more.
When the temperature increases to a certain degree, transpiration, photosynthesis, and respiration also increase. When combined with the length of the day, temperature also affects the change from vegetative or leafy to reproductive or flowering growth. Depending on the situation and the kind of plant, the temperature can either speed up or slow down this transition.
Germination
The temperature needed for germination is dependent on the species of plant. Typically, cool-season crops such as lettuce, spinach, and radish germinate optimally at 55° to 65°F, while warm-season crops like lobelia, tomato, and petunia germinate most at 65° to 75°F.
