Pollination ecology of 10 Asclepiads viz. Calotropis procrea (Ait.) Ait.f. ssp. hamiltonii, Glossonema varians (Stocks) Hook.f. oxystelma esoulentum (Linn. f.) R. Brown, Pentatlropis nivalis (Gmel.), Field and Wood, Pergularia daemia (Forssk.) Chiov.,
Pergularia tomentosa L. of tribe Asclepiadeae and Caralluma edulis (Edgew.) Benth., Carralluma tuberoulata N.E.Brown, Ceropegia bulbosa Roxb. and Leptadenia pyrotechnica (Forssk.) Decne. Of tribe Ceropegieae has been carried out from Pakistan. In this connection floral phenology and morphology, location of germination locus, in-vitro pollinium germination, floral visitors and their pollnium load, level of pollinator activity in natural populations, mechanism of pollinarium removal and pollinium insertion, pollen ovule ratio and ratio of pollen grains per pollinium to ovules per carpel have been studied.
Andromonoecy is being reported for the first time in Glossonema varians (Stocks) Hook f. and in the family. Flower life of the studied taxa is usually short ranges only from 1-3 days.
A variety of structural adaptations have been revealed in response to the mode of pollination, particularly in pollinium morphology and orientation, stigmatic chamber, coronal elements, nectaries and nectar location and presentation.
It has been demonstrated that pollinarium removal and pollinum insertion are specialized processes rather than a chance and exhibit definite relationship with the specialized floral
modifications. Apart from presence of residual corpusculum and narrowness of stigmatic chambers. other three factors like closing of stigmatic chamber. presence of glandular papillae in the stigmatic chamber, and anther wings are reported to be responsible for the proper and successful insertion of the pollinium into the stigmatic chamber. A correlation between pollinarium removal and pollinium insertion exist and thus revealed that pollinium insertion rates are the positive function of removal rates.
Pollinators (insects) are species as well as tribe specific. Calotropis procera (Ait.) Ait. f. ssp. hamiltonii (Wight) Ali is regarded as Xylocopa blossom (Meljttophilous), Glosscsonema varians (Stocks) Hook. f. and Oxystelma esculentum (Linn.f.) R Brown as bee and wasp blossom (Melittophilous),PentatropiS nivalis (Gmel.) Field and wood, Pergularia daemia (Forssk.)
Chiov. ,and Pergularia tomentosa L. as bee and moth blossom (Melittophilous and Phalaenophilous). Ceropegia bulbosa Roxb. As fly blossom (Myophilous) and Leptadenia pyrotechnica (Forssk.) Decne.as fly and beetle blossom (Myophilous and Cantharophilous).
The germination locus of the pollinium seems to be correlated with the flower structure and pollination mechanism of the species. Pollinium of each species required a specific sugar concentration for optimal germination (in vitro pollinium germination) which is more or less similar to its floral nectar sugar concentration.
A relationship has also been observed between pollinium vigor (in - vitro), pollinarium removal and pollinium insertion with respect to flower age. However. pollinium vigor and pistil receptivity did not change significantly with the flower age.
Low pollen ovule ratios seems to be the characteristic feature of Asclepiads. Pollen ovule ratios have been correlated with a number of floral characters, pollinator type and pollinator activity.
Number of floral and particularly reproductive characters such as pollinium orientation and morphology, germination locus, pollinator type, pollinator activity and pollen ovule ratios provide additional evidence in support of the tribal classification.
It has been concluded that Asclepiads possess a high degree of synorganization of variety of structural elaborations and functional process of pollination.