Biennials that flower in one instead of two years grass that stays green during the winter instead of turning brown are only two of the dramatic effects on plants caused by the new growth stimulant, gibberellic acid.
Since the first progress report to readers appeared in the May 1957 issue of FLOWER GROWER, research has been intensified.
Today, gibberellic acid, the best-known gibberellins, is considered the most important discovery in agriculture during the past twenty-five years.
As noted in May, the Japanese discovered and isolated gibberellic acid over 20 years ago from the fungus Gibberella fujikuroi found growing on rice plants.
They observed that plants infected with the fungus grew more vigorously than non-infected plants.
Present-day Application Methods
Present-day application methods include overall spraying or dusting of plants, lanolin suspensions daubed on local areas such as growing tips or dipping seeds or bulbs in a gibberellic acid solution. Soil applications have not proved as promising as direct application to plants or seeds.
One word of caution should be given. Home gardeners and particularly commercial growers should remember that the material should be used on an experimental basis on a limited number of plants until specific recommendations for use are released.
Many factors influence plant responses to gibberellic acid. These include the particular plant species or variety, mineral nutrition, light, temperature, plant age when treated, treatment pattern, site of application, and dosage. Not all effects of application have been found desirable.
Some of gibberellic acid’s more interesting and significant effects are listed below.
Flowering
Speeds blooming of many ornamentals, including aster, foxglove, geranium, cosmos, pansy, and delphinium. Some vegetables include cabbage, dill, lettuce, turnip, beet, and pepper.
It is interesting to note that the treated plants continue to grow and flower after treatment even though they normally might require either a long or short day or a cold period before blooming.
Many biennials can be made to flower and fruit like annuals, although they must still be grown at or near the temperature normally needed for flower induction.
Petunias, when treated, flowered in midwinter under short days, whereas they normally require long days to flower.
Pansies flowered 25 days after a single application to plants grown from seed sown on November 5. This is considerably faster than untreated plants.
Seed Production
True biennials, such as sugar beets, when treated with gibberellic acid, produced seed the first year, which is a tremendous timesaver for commercial seed producers.
Treat lettuce and cabbage “bolt” and produce flowers and seeds without going through the normal heading stage.
Treated celery produces seeds with only a short period of low temperature. Earlier flowering of ornamental biennials may have practical value for home gardeners.
Faster emergence of seedlings is of particular value early in the season when soil is often cold and wet.
Found to emerge faster when treated were peas, beans, corn, soybean, cotton, sugar beet, and many ornamentals. The effect on seedlings is to make them grow faster and taller.
This may give a stretched look, which would be undesirable if it continued. However, this rapid early growth is only apparent for a short time and is an advantage early in the season when cold, wet weather often causes seedlings to stand still.
Breaking Dormancy
Hydrangeas normally require six weeks of cold storage to break dormancy. This time may be greatly reduced or eliminated by treatment.
Dormancy of Irish potatoes, when freshly dug, can be overcome by soaking in gibberellic acid. Seed pieces, when planted, sprout immediately. Seeds of some plants have been shown to respond similarly.
Miscellaneous Effects
The size of grape clusters can be increased. On treated plants, the stems grow longer and provide more room for individual grapes to form; this eliminates hand thinning. This development may be an important step towards the possibility of mechanically harvesting grapes.
Because of the longer stem, there is more space for a mechanical cutter to sever the hunch from the vine without damage.
Stems of treated strawberries grow longer, which helps to raise the fruit from the ground and avoid rots and molds.
Pasture and Lawn Grass
Pasture and lawn grasses turn green and grow earlier in spring and fall following treatment. Winter cover crops may be established despite cold weather.
Bush Beans
Some dwarf plants, such as bush beans, grow to resemble pole beans.
Tomato Fruits
The amount of fruit on tomatoes has increased even in the absence of pollination, and yields of some vegetables have increased.
Effects of Temperature
High temperature is often detrimental to a plant’s growth or fruit set.
For example, in the South, tomatoes often set fruit that does not crow; in the North, peas won’t set in midsummer. These effects have been partially overcome by treatment.
Gibbet-Celtic Acid
Gibbet-Celtic acid is not a cure-all or magic formula that will solve all plant growth problems.
However, many useful applications are being developed, and the future of its importance to agriculture appears extremely promising.
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