Physical and biochemical characteristics of Parkinsonia aculeata L. and Pongamia pinnata Vent. flowers
K L Jain; H R Dhingra
Parkinsonia aculeata and Pongamia pinnata are important summer food plants for a variety of wild solitary and social bees (Apoidea) in northern India. Studies were thus carried out on these two species in Hisar, India, in order to assess the relative importance of various physical and biochemical characteristics of the flowers in regulating nectar foraging by bees. The nectar of P pinnata is accessible directly through the corolla tube either at a place between the keel and the standard petal or at the sides of the standard petal. P aculeata has a conspicuous flag petal marked with red spots which guide foraging insects to the nectary. Colorimetric analysis showed that P aculeata flowers contained higher quantities of UV-reflective carotenoids than those of P pinnata. P pinnata flowers secreted 1.05 ± 0.06 III nectar containing 34.8% sugars, with almost equal amounts of sucrose and glucose, within 2-3 h of anthesis. In the same period, P aculeata flowers secreted 0.24 ± 0.08111 nectar containing 30.2% sugars, predominantly glucose and fructose. Analysis of pollen, carried out using anthers on the verge of dehiscence, showed that P aculeata pollen was richer in soluble sugars and free amino acids than the pollen of P pinnata, but lower in protein. It is concluded that P pinnata could be used to combat the summer dearth period in semi-arid areas.