Studies on growth ,flowering ,fruit set and fruit development in nutmeg (Myristica fragrans hout.)

Abstract

The present investigations were carried out in the College of Horticulture, Kerala Agricultural University during the year 1978-’79. The object was to study the pattern of growth and flowering, floral biology, fruit set, fruit drop and fruit development in nutmeg. The studies were conducted on male and female trees of about 17 years old receiving cultural practices as recommended by Kerala Agricultural University. Shoot growth in nutmeg was found to be cyclic, a period of growth followed by a quiescence. Six flushes were observed during the period of one year. All the flushes were not seen in all the shoots which resulted in continuous growth in nutmeg. The mean growth varied significantly from month to month, with minimum in summer months. Two peaks were observed in May, June and September. Nutmeg trees were found to be slow growers when compared to other prerennial trees. Flowering pattern of male and female trees differed. There was monthly variation in the extent of flowering of both male and female trees. In females, flowering was constrained to seven months whereas in male, flowering was observed through out the year. Maximum flowering in both the cases was in July followed by October. The flower bud development in male and female trees followed specific pattern. The male flowers took only about half the period taken by the female flowers to develop. The female flowers took 154 days for complete development. Three types of flowers were observed in nutmeg which resembled and differed each other for different characters. In male flowers, peak anthesis was between 1900 hours and 0100 hour and in females, it was between 2100 hours and 0300 hours. Anther dehiscence occurred about 24 hours prior to anthesis. The stigmatic receptivity lasted for six days after anthesis with the maximum for the first three days. The chief agent of pollination was wind. Anther number and pollen production per flower varied from tree to tree. Sucrose at concentrations of 2, 4, 6 and 8 per cent, boric acid and calcium nitrate at concentrations of 25, 50, 75 and 100 ppm each were found to promote pollen germination. A combination of the three (4% sucrose, 25 ppm calcium nitrats and 75 ppm boric acid) gave maximum germination (96.9%). Pollen was found to be viable for three days in the dehisced bud condition and the viability was greatly reduced thereafter. The percentage set varied for different trees and for different aspects with maximum set on Western and eastern aspects. Hand pollination increased the percentage set than open pollination, indicating the possibilities of assisted pollination for better production. There was no apomictic fruit development. The mean percentage drop after set was 74.4 per cent. The number of fruits harvested accounted to only 8.47 per cent of the total flowers produced. The period of maximum drop after set coincided with the period of maximum development of the fruit. The fruits attained maturity in 206 to 237 days after fruit set. The developing fruits followed a sigmoid growth pattern. The peak harvest season ranged between April and July. The trees varied for the percentage drop and number of fruits harvested.