Models to study pollen allelopathy

To develop models for pollen-pollen interactions, the effects of allelochemicals secreted by foreign pollen i.e. donor pollens were studied in vitro or in vivo on the germination of acceptor-pollen and autofluorescence. Both acceptor and donor pollens were choosen from the indoor (greenhouse) and outdoor grown plants. Microspores from Hippeastrum hybridum, Philadelphus grandiflorus, Knautia arvensis, Plantago major and Oenothera biennis were used as pollen-acceptors, while other pollen grains from 42 spp. -as donor pollens. The significant negative effects of donor pollen were observed on 3 acceptor pollen: Hippeastrum hybridum, Philadelphus grandiflorus and Knautia arvensis. Their germination was inhibited by forein pollen grains from 18 spp. In mixtures of pollen from various species, 4 donors pollens (Alstroemeria aurantiaca, Anthriscus sylvestris, Solidago virgaurea and Tagetes patula) stimulated the microspores’ germination, whereas, microspores from Aloe vera, Lilium mortagon, Filipendula ulmaria and Hypericum perforatum showed no significant responses to foreign pollen. The rate of the pollen tube formation was also changed in donor pollens themselves in the presence of acceptor pollen grains. Coloured excretions from donor pollen of Hypericum perforatum and Calendula officinalis stained the Colourless pollens of Plantago major and Oenothera biennis. Autofluorescence of acceptor and donor pollens in mixtures was changed to bluegreen and red spectral regions that may serve as the indicator response on forein microspores. Generally increased blue-green and occasionally red emission indicated the decrease in rate of pollen germination. However, red fluorescence was not related to germination and depended more on species used.