Remediation after excessive application of paclobutrazol

Recently, I saw the question raised by Pan Zhijing in the 6th issue of Chinese Orchid in 1994 that the orchid stopped growing because of excessive application of paclobutrazol. Comrade Gu Jun gave an answer in the third issue of 1995. I would also like to talk about my views here.

When it comes to paclobutrazol, plant hormones should be linked first. There are five hormones in plants, and gibberellin is one of them. One of the physiological functions of gibberellin is to promote cell elongation, resulting in plant growth and leaf elongation. Gibberellin can be biosynthesized after a very complex process in plants. After the research of scientists, paclobutrazol inhibits the enzyme activity of the three steps in the process of gibberellin biosynthesis, so the gibberellin content is reduced and the plant growth is delayed. Paclobutrazol is an inhibitor of gibberellin biosynthesis, not a poison.

After applying excessive paclobutrazol to the orchid plant, it can be remedied by the following methods.

First, when paclobutrazol is applied, the orchid plant is inhaled through the roots or leaves in a short time (a few minutes to more than ten minutes), and it cannot be washed away with water. If left untreated, paclobutrazol in the orchid plant will gradually decompose into substances with no inhibitory effect, and the plant will slowly resume growth. According to the principle that paclobutrazol inhibits gibberellin biosynthesis and makes the plant lack of gibberellin, after excessive application of paclobutrazol, gibberellin solution can be sprayed 500-1000ppm), once a week, 3 times. With the increase of gibberellin content in the body, the orchid plant can resume its growth.

Second, the replacement of plant materials is also a necessary measure. The residual period of paclobutrazol in soil is very long, usually in half a year to a year or even for a long time, of course, with soil texture and temperature. It has something to do with rainfall. After spraying excessive paclobutrazol, the plant material can be changed, more paclobutrazol plant material can be abandoned and replaced with new plant material without paclobutrazol, the orchid plant can grow normally.

Third, on the basis of spraying gibberellin, the application of urea and potassium dihydrogen phosphate solution can promote growth.

Finally, remind Lanyou that the concentration should be carefully considered when using plant growth regulators, it is better to be dilute rather than concentrated (generally 1OO-1000ppm), and would rather be sprayed twice. During the application, one or two orchids were used in the preliminary test, and only after three or five days without burns or other abnormal phenomena could they be applied on a large scale.

[editor's note: professor Pan Ruichi is a professor in the Department of Biology, Shipai South China normal University, Guangzhou City, Guangdong Province, and is the first tutor of doctoral students in China to study the burial of orchid peanuts. Mr. Ye Qing, the first doctoral student who studied orchid physiology, stayed at school after graduation and is now an associate professor.] (pan Ruichi)