Advanced Nutrients Founder and CEO Mike Straumietis says that environmental factors affect plant growth. For instance, only plants adapted to limited amounts of water can live and thrive in deserts. Most of the time, poor environmental conditions, such as too little water, can damage a plant directly. Environmental stress sometimes weakens a plant, thus making it more susceptible and vulnerable to disease or insect attack.
In this blog post, Mike Straumietis shares some of the biggest environmental factors affecting plant growth.
Three characteristics of light affect plant 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. Plants look green because they reflect, rather than absorb, green light.
The quantity of light means the intensity or concentration of sunlight, which varies with the seasons. The maximum amount of light can be found during the summer, while the minimum amount is 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 duration, otherwise known as photoperiod. This refers to how much time a plant is exposed to light. This amount of time controls flowering in many plants. This is why plants are described as short-day or long-day, depending on what conditions they flower under. However, 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.
While some plants don’t fit into any category, they may, in fact, 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.
Temperature influences the majority of plant processes. These processes include respiration, photosynthesis, transpiration, 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.
The germination temperature depends on the plant species, explains Mike Straumietis. Typically, cool-season crops like 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.
There are times when horticulturists combine temperature with day length to manipulate flowering. Take, for instance, a Christmas cactus. This plant forms flowers due to a mix of short days and low temperatures. To facilitate the blooming of a Christmas cactus, 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.
Plants that thrive in cooler seasons, 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.
Cooler temperatures decrease 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, on the other hand, can cause stunted growth and low-quality vegetables. An example would be high temperatures that lead to the taste of lettuce becoming more bitter, Mike Straumietis adds.