Interaction of temperature and growth retardants on pimento pepper

The effects of temperature and growth retardants were studied on pimiento pepper. Seedlings were subjected to night temperatures of 12°-13°C or 20°-21°C for 21 days after the appearance of first true leaves. Drench and foliar application of the growth retardants (2-chloroethyl) trimethylammonium chloride (CCC) and N-dimethylamino succinamic acid (SADH) at concentrations of 10⁻²M, 10⁻³M and 10⁻⁴M were made at the 2, 4-6 and 6-8 leaf stages of growth. In the greenhouse, interaction of temperature and growth retardants resulted in an increase in number of flower buds and fruits set and subsequently enhanced flower and fruit development and fruit ripening. Treated plants were shorter, greener and had more extensive root systems than untreated plants. Control of plant growth occurred during the early stages by the retardation of internodal elongation in the sub-apical region. Morphological and anatomical observations indicated that the increased stem diameter of treated plants resulted from an increased amount of conducting tissue and enlarged pith region. Under field conditions, interaction of temperature and growth retardants resulted in significantly higher early yield of ripe fruits. Plants that had been exposed to cool temperature in the seedling stage yielded slightly less than those which had been exposed to warmer temperature. Application of growth retardants to plants which had been exposed to the cooler temperature in the seedling stage resulted in higher total yield. CCC seemed to be more effective than SADH in this regard. Results indicated that pimiento seedlings were more sensitive to the interaction at the higher concentrations and early leaf stages. Since these interactions did not result in a phytotoxic effect on plant growth and ultimate yield, commercial use of CCC could be an advantage in growing pimiento transplants. Transplants with better developed root systems, shorter and thicker internodes could be grown in cooler areas where night temperatures go down to 12°-13°C. This would help to overcome the problem of over sized transplants which impair mechanical transplanting and also possibly lower the cost of transplant production. The early application of CCC (at the 2-leaf stage) may produce a significantly higher early marketable yield by 10-12 days, which would bring a higher price for the pimiento growers.