The application of plant growth regulator on flower and nursery stock
Plant growth regulator will become one of the five new technologies (clone, certified seed, soilless factory farming, chemical control agent and herbicide) in the agriculture industry in the future. It has become a big task in modern biotechnology by adjusting and controlling the growth, development, blossom and fruit bearing with plant growth regulator according to people’s requirements. Especially it will have very broad prospect by using plant growth regulator on landscape plant. Currently, plant growth regulator still has been used very little on flower and nursery stock and only has been partially used on cell tissue culture. Therefore, by mastering and using this new technology ahead of time, it will be of great significance in improving flower nursery stock production and maintenance quality and reducing cost.
a.What is plant growth regulator?
Plant growth hormone has broad and obvious physiological effect as well as will have strong regulating effect on plant growth and development. Since plant growth hormone was firstly discovered, people wanted to use it on the agriculture production. However, as the hormone content that exists in the plant body is very little, it will be difficult and uneconomical to extract hormone from plant body and use it on agriculture production. Therefore, scientists have tried to concentrate and extract this kind of hormone by using microbial fermentation method or synthesize the substance that has physiological activity by using chemical methods. Some of the substances may not exist in the plant body as well as the chemical property also may not be similar with plant hormone. However, as it may have similar physiological activity with plant hormone, it will also have important regulating effect on plant growth and development. This kind of artificially synthesized and artificially extracted physiological activator can be called plant growth regulator.
Plant hormone is a kind of normal metabolite that is generated by the induction of specific environmental message and is also a kind of endogenous active material that is generated in the plant body, which can be transferred to other organizations and tissues from the synthetic organizations or tissues. Although it has little content in the plant body, it will have important effect and can regulate various physiological activities of plant, which is an indispensable substance in plant life activities. Besides, it also can regulate and control plant germination, rooting, growth, organ differentiation, flowering, fruit bearing, maturity, falling off and dormancy. Without plant hormone, plant cannot grow or develop normally and will even die.
By using very low concentration of plant growth regulator (only a millionth concentration), it will have important regulating effect on the growth, development and metabolism of plant. Besides, by using plant growth regulator, it can solve some problems that are difficult to solve by cultivation techniques, such as breaking dormancy, adjusting gender, promoting blossom, chemical training, preventing fruit drop, promoting rooting, improving resistance and so on.
c. Classification of plant growth regulator
Currently, the recognized plant hormones mainly include 5 types, which are auxins, gibberellins, cytokinin, abscisic acid and ethylene. In addition, scientists also have discovered other endogenous growth regulating substances that have plant hormone function, such as brassinolide, salicylic acid, jasmonic acid and so on.
d. The application of plant growth regulator on the production of flower and nursery stock
Plant growth regulator can be used in promoting cuttage, rooting and germination.
Plant growth regulator can promote rooting, which can be reflected in the following three aspects.
a. Promote cuttings rooting, which means that it can promote the forming of root primordial in cutting base and accelerate rooting speed.
b. Promote rooting after transplantation, which means that it can activate the activity of root primordial, promote fast rooting and improve transplanting survival rate, such as root motivation.
c. Promote mound layer rooting. Mound layer is often used in breeding those plants that cannot take root or are difficult to take root. (For example, after the ringing treatment of branches, indole butyric acid lanolin cream will be smeared on the ringing parts, moss will be added so as to keep wet as well as plastic film will be packaged, thus it can promote rooting. After rooting, the branches will be separated from the stock plant and will be inserted in the seedbed.)
Regulators that can promote rooting mainly include NAA, IBA and NAA+IBA. Among them, root that induced by NAA will become short and thick and will appear to be brush shape; the adventive root that induced by IBA will become thin and long, therefore, by combining these two regulators, it will have good effect on promoting rooting; besides, daminozide, IAA, naphthalene acetamide and 6-BA also can promote rooting. Except for the matching of the above mentioned substances, some cofactors, such as vitamin, sugar, sanitizer and penetrant also will have very important effects. The well-known rooting agents that have guaranteed quality all have been used for years in the practical production, besides, they have reasonable matching and are all added with various cofactors, such as the “root motivation” that used in promoting surviving in tree transplanting. In the practical production, plant growth regulator can be used in the cutting rooting of oriental arborvitae, Japan Euonymus, azalea, cyclamen, poinsettia, geranium, aspen, birch, elm, Chinese pink and chrysanthemum. When using the rooting agents, we should pay attention to the working concentration as high concentration will inhibit rooting, while the low concentration will have no rooting effect.
b. Plant growth regulator can promote seed germination and break dormancy
In order to keep away from bad environment, plants often survive under dormant state. Most of the plants will have a dormancy period. Therefore, in order to break dormancy, the content of growth promoters should be kept higher than the inhibiting substances in the plant body. In the practical production, gibberellin and cytokinin are the two kinds of most effective germination promoters that can break dormancy and promote germination. For example, by spraying gibberellin on the bulb of lily, it will sprout after being stored for 6 days; by spraying 100ppm gibberellin on azalea, camellia and peony, it can break dormancy and promote germination. Besides, gibberellin is also often used in breaking dormancy and promoting germination of narcissus, tulip, chrysanthemum, beech and gentian.
In addition, except for the external conditions that can influence the development of corm (such as temperature, humidity and climate), by spraying plant growth regulators, such as 6-BAP or gibberellin, it also can break corm dormancy and promote corm development. By spraying NAA+6-BAP on wild lily, it can promote the formation of small bulb and promote flowering. Abscisic acid and MH can extend dormancy period and postpone flowering.
c. Plant growth regulator can regulate flower season and promote flower formation
It is particularly important for regulating the flower season of ornamental plant. In order to meet the demand of market and festival as well as control the flowering time of flowering plant and delay or promote flowering, except for light, temperature and fertilizer regulation, plant growth regulators (flower-forcing agent) can also be used in inducing flowering and increasing flowering. For example, by using regulator on tulip when the plant height reaches 5-10cm, it can bloom ahead of time, besides, by dripping ethephon on the leaf axil of ornamental bromeliads, it can induce flowering. In addition, daminozide, CCC and MET also can promote flowering, which are widely used in woody ornamental plants, such as peony, camellia, rose and so on. By using gibberellin, it can promote flowering of violet, primrose, camellia, clove, tulip, angelica dahurica, geranium, Chinese pink, azalea, narcissus, aztec dahlia, cyclamen, gladiolus and begonia. By using daminozide, IBA, NAA and PP333 on azalea, poinsettia, bryophyllum, chrysanthemum, carnadine and fuchsia, they can delay flowering.
d. Plant growth regulator can shape and dwarf plant as well as improve ornamental value.