Blackwelder column: Plants need hormones, too
Just as hormones are important for growth and development of animals, including humans, they are also important for plant growth and development.
Biochemical compounds are instrumental in controlling the growth and development in all plants. Produced in very small amounts, plant hormones are synthesized in one place and take effect in another, often in very minute concentrations.
Plants produce a vast array of hormones with varying functions ó too many to list here. Plant scientists have discovered they can synthesize these chemicals to alter and change plant growth.
For example, auxins are growth hormones produced by plants to promote cell growth and stem elongation, but may also inhibit growth. Plant scientists have taken this mode of action and developed synthetic herbicides used for controlling lawn weeds.
Flower producers often use growth regulators to keep plants dwarf and compact, which is a standard practice on bedding plants in early spring. Growth regulators or hormones decrease length on nodes, making plants compact, reducing legginess and producing an attractive, marketable plant.
Growth regulators applied on clipped hedges help maintain a fresh-clipped appearance during the summer growing season while reducing rapid growth. There is even a growth regulator used that eliminates growth of grasses, reducing maintenance with string trimmers. Many who maintain high visibility areas incorporate this practice into their maintenance programs.
Flowering plants, including shrubs such as camellias, roses and azaleas often respond to flowering hormones. Some growth regulators that increase flower size and intensity are called gibberellins. Camellia enthusiasts treat buds with gibberellic acid before flowering, often doubling the normal size of the blooms.
Ethylene is the only known gaseous hormone produced by plants. Usually, it inhibits vegetative growth reducing leaf area in drought conditions and accelerates fruit ripening and dropping. Ethylene is released by ripe fruit and is used regularly by commercial food handlers to speed the ripening process of tomatoes, apples and bananas.
Salicylate, a hormone found in willows and used commercially to produce common aspirin is now recognized as a growth regulator. This old compound is now thought to promote disease resistance and increase flower longevity in some plants.
Sometimes nature throws us a curve and hormones become unbalanced, causing strange things to happen, such as premature bloom. Unusual weather patterns, drought, cold weather and physical damage alters plant hormones, especially flowering hormones.
Unseasonable weather is usually the culprit to our fall blossom preview. Premature blooming may have an effect on the normal bloom period again in the spring. However, it will not be detrimental to growth and development. What these plants need is something we all need ó a normal winter and an average summer. Until then, we will continue to see more confused plants around the county.
Darrell Blackwelder is an agricultural agent in charge of horticulture with the North Carolina Cooperative Extension Service in Rowan County; phone, 704-216-8970.