Association of floral traits on pollination effectiveness of insects foraging on psidium guajava (guava

Abstract

Plant-pollinators are mutualistic relationships where both are dependent and benefit from each other. In order to ensure successful pollination, it is important to have good flower conditions and pollen quality to attract pollinators to forage on flowers. To understand the association of floral traits on guava pollination, general characteristics of guava tree were described. Flowers and pollen grains of Psidium guajava cultivars and Psidium cattleianum were analyzed and measured for their appearance, shape and sizes. Pollen grains viability were measured with colorimetric method using 2,3,5-triphenyl tetrazolium chloride (TTC) and Iodine Potassium Iodide (IKI) staining solution. Guava flowers are white with multiple of five petals arranged in two whorls for P. guajava but only one whorl for P. cattleianum. The guava pollen grains were small, triangular amb, tricolprates, brevicolpate aperture type with exine pattern of granulate/scarbate in all P. guajava cultivars but rugulate pattern in P. cattleianum. There are slight differences in morphology particularly in sizes and numbers of certain aspects among cultivars and species which may be the result of coevoluation with their pollinators. The IKI is the better staining solution as it produces a higher viability percentage (>85%) compared to TTC staining. Kim Choo White has the highest pollen viability among P. guajava cultivars studied. Meanwhile, field observations on pollinator visitation frequencies and pollen carrying capacity were conducted at intervals of 2 hours from 0900 h to 1600 h in 5 and 3 random sampling sessions, respectively, from January to October 2022, to identify efficient pollinator species for guava and understand their behavioural that resulted in successful pollination. The most common pollinators that visit guava were Xylocopa latipes, Xylocopa aestuans, Apis dorsata, Apis cerana, Heterotrigona itama and Ceratina lieftincki. It was determined that the insect’s body size positively influenced the pollen carrying capacity. Bees from genus Apis and Xylocopa were found to be efficient pollen carriers and visited more guava flowers compared to the other pollinators.