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Abstract
Concentrations from 50 to 1,600 ppm gibberellic acid (GA3) 20 to 100 ppm naphthaleneacetic acid (NAA) and 500 ppm 6-benzylamino purine (BA) were sprayed either once on cherimoya (Annona cherimola Mill.) flowers in anthesis or 5 times on fruits at 3-week intervals commencing with anthesis to study their use as growth promotors. Only GA3 significatively enhanced fruit set and stimulated growth of seedless fruit. No synergism was found between GA3 and NAA and BA was antagonistic to GA3 relative to fruit set. Growth curves followed a double sigmoid pattern for fruits treated both naturally and chemically. GA3 induced severe cracks on fruits before harvest which makes its application impossible for practical purposes at the present state of this investigation. Cracking was not related with differential growth rates induced by hormonal treatment or absence of seeds. A possible role of GA3 on the determination of the secondary wall pattern, as observed on fruit stalk tissues, is suggested as one of the causes contributing to fruit cracking.
Abstract
Preliminary research to investigate additional factors to increase results obtained by hand pollination in cherimoya (Annona cherimola Mill.) revealed that the first flowers to open gave a poorer fruit set with hand pollination than later ones. Flowers that opened earliest had the majority of the pollen grains in the tetrad stage with thick walls, full of starch and did not germinate. Flowers that opened later had a greater proportion of individual pollen grains, no starch grains, and greater cytoplasmic streaming. Many grains germinated after a few hours.