As Advanced Nutrients Founder and CEO Mike Straumietis points out, plants are greatly affected by environmental changes.
Whether directly or indirectly, many plant problems are caused by environmental stress. There are instances when poor environmental conditions, such as too little (or too much) water, damage a plant directly. In other cases, environmental stress weakens a plant, making it more susceptible to disease or insect attack.
Several environmental factors affect plant growth. Take, for instance, light.
With light, there are principal characteristics that affect plant growth. These characteristics are 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 two lights have the greatest effect on plant growth. Blue is responsible mainly for vegetative or leafy growth, while red encourages flowering when combined with blue light.
As for the quantity of light, it pertains to the intensity or concentration of sunlight, and this varies with the seasons. The maximum amount of light occurs during the summer, whereas the opposite can be found in 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 point.
Then, there’s photoperiod, the duration of exposure to light. This amount of time controls flowering in many plants. 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 says that it is not the length of the photoperiod but rather the length of uninterrupted periods of darkness that is crucial to floral development.
The short-day (long-night) plants form flowers only when the day length is less than about 12 hours. Many plants that flower in the spring or fall are in this category. Meanwhile, long-day plants form flowers only when the day length exceeds 12 hours. Most of the plants that flower in the summer are long-day plants. Plants that are day-neutral aren’t dependent on day length. These are plants like corn, tomato, and cucumber.
Some plants don’t fit into any category, Mike Straumietis explains, but may respond to combinations of day lengths. A perfect example of this would be petunias, which bloom regardless of day length but do earlier and more profusely with long days.
Another environmental factor that has a huge effect on plants is temperature.
Temperature influences most essential plant processes, from respiration to photosynthesis to transpiration to germination and flowering. When the temperature increases to a certain degree, transpiration, photosynthesis, and respiration go up. When combined with the length of the day, temperature also affects the change from vegetative or leafy to reproductive or flowering growth. According to Mike Straumietis, depending on the situation and the specific plant, the temperature can either speed up or slow down this transition.
Let’s look at germination, temperature, and the kinds of plants. Typically, cool-season crops such as lettuce, spinach, and radish germinate best at 55° to 65°F, while warm-season crops like lobelia, tomato, and petunia germinate optimally at 65° to 75°F.
As for flowering, in some cases, horticulturists combine temperature with day length to manipulate flowering. For instance, a Christmas cactus forms flowers due to a mix of short days and low temperatures. To facilitate the blooming of a Christmas cactus, you can place it in a room with over 12 hours of darkness every day and a temperature of 50° to 55°F until the flower buds form. Cool-season plants like spinach will flower when temperatures are high and the days are long. However, if temperatures are too low, the fruit will not be set on warm-season crops like tomatoes, Mike Straumietis adds.
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