Pollen production, fertility and compatibility studies in shoe flower (Hibiscus Rosa-Sinensis L)

Abstract

Investigations were conducted on the pollen morphology, production, fertility and compatibility in 34 types or varieties of Hibiscus rosa-sinensis L. and two other species viz., H. mutabilis L. and H. schizopetalus Hook, in the Department of Pomology and Floriculture, College of Horticulture, Kerala Agricultural University, during the year 1981-‘83. Since the types maintained did not possess any distinct varietal names, detailed morphological descriptions were made for identification. Observations were also made on certain aspects of blossom biology like flower opening, anther dehiscence, folding of corolla and retention of corolla. There was distinct variation in the morphology of flowers in the 36 types/varieties or species studied. Flower opening took place during the morning hours and in most of the types/varieties/species anther dehiscence commenced soon after flower opening. The time taken for the folding of the corolla ranged from 12 to 36 hours after flower opening and for the retention of corolla ranged from 24 to 72 hours. Pollen grains of Hibiscus were pantoporate, spheroidal and spinose and were 125.91 to 198.58 microns ( µ) 0 / in diameter. Pollen production per anther varied from 87 to 500 and percentage of pollen fertility ranged from 4.6 to 97. 4. Standardization of media for pollen germination and tube growth indicated that a medium consisting of 20 per cent sucrose + one per cent agar + 100 ppm boric acid was the best. The pollen grains commenced germination within 30 minutes of dusting and gave satisfactory germination even after four hours of incubation in the best medium. Of the 35 types/varieties/species tested, only in 23 cases, pollen germinated ,In vitro. Acc.11 showed maximum germination of 85.8 per cent followed by H. Mutabilis and Acc.2 while tube length was maximum in Acc.2 (962.48 µ) followed by Acc.11 and H. mutabilis. Polysiphonous germination was observed in majority of cases. Pollen grains could not be stored for more than three days in any of the methods employed in the present study. Of the different methods tried, storage of flowers with anther column intact at 4°C over calcium chloride in a desicator was found to be the best followed by storage of flowers at 4°C without calcium chloride. Acc.26 and Acc.11 had the longest shelf life followed by Acc.2. It was found that only Acc.2 and g. mutabilis set fruits naturally. Out of the seven types/varieties of H. rosa sinensis and two other species viz., H. mutabilis H. schizopetalus selfed, only-in five types or varieties of H. rosa-sinensis and in the species mutabilis self compatibility was noticed. The fruits matured in 28 to 38 days and germinated in 10 to 18 days. The number of seeds per capsule ranged from 8.5 to 192.5 and seed germination ranged from 3.33 to 69.77 per cent. Survival percentage of germinated seedlings was more than 95 per cent. Out of the intraspecific cross combinations tried, compatibility was observed in all the crosses except in cases where Acc.11 was used as the female parent. The cross Acc.2 x 11 had the highest crossability index followed by Acc.2 x 18, 2 x 26, 18 x 11, 22 x 11, 26 x 2 and 26 x 11. Interspecific compatibility was practically absent.