Experimental insights on the function of ancillary pollen and stigma polymorphisms in plants with heteromorphic incompatibility.

Most heterostylous plants possess a reciprocal arrangement of stigmas and anthers (reciprocal herkogamy), heteromorphic self-incompatibility, and ancillary polymorphisms of pollen and stigmas. The topographical complementarity hypothesis proposes that ancillary polymorphisms function in the rejection of incompatible pollen thus promoting disassortative pollination. Here, we test this hypothesis by investigating patterns of pollen transfer and capture in populations of dimorphic Armeria maritima and A. pubigera and distylous Limonium vulgare (Plumbaginaceae), and by studying pollen adherence and germination patterns in A. maritima following controlled hand-pollinations. Armeria lacks reciprocal herkogamy allowing the evaluation of the extent to which ancillary polymorphisms affect the composition of pollen loads. We compared the amounts of compatible and incompatible pollen on stigmas in natural populations and calculated the proficiencies of pollen transfer for each mating type. We detected disassortative pollination in each species, and mating types did not differ in compatible pollen capture, although cob stigmas captured more incompatible pollen. Controlled hand-pollinations revealed the failure of incompatible pollen to adhere and germinate on stigmas. Our results provided evidence that, while structural in nature, pollen-stigma dimorphisms are tightly associated with heteromorphic incompatibility and likely function to promote disassortative pollination, especially in the absence of reciprocal herkogamy.

Comparative study of three Plumbago L. species (Plumbaginaceae) by microscopy, UPLC-UV and HPTLC.

This paper presents a comparative study of anatomy of leaves, stems and roots of three species of Plumbago, namely P. auriculata Lam., P. indica L. and P. zeylanica L. by light microscopy. The paper also provides qualitative and quantitative analysis of the naphthoquinone, plumbagin-a major constituent present in these species-using UPLC-UV. Microscopic examinations revealed the presence of distinctive differences in the anatomical features of the leaf, stem and root of the three species, and these can thus be used for identification and authentication of these species. UPLC-UV analysis showed the highest concentration of plumbagin in the roots of P. zeylanica (1.62% w/w) followed by the roots of P. indica (0.97% w/w) and then P. auriculata (0.33-0.53% w/w). In contrast, plumbagin was not detected in the stems and leaves of P. indica and in the leaves of P. auriculata, whereas very low concentrations (<0.02% w/w) of plumbagin were detected in the stems and leaves of P. zeylanica and in the stems of P. auriculata. HPTLC fingerprints of the leaf and root of the three species exhibited distinguishable profiles, while those of the stems were undifferentiated.