Interspecific Pollen-Pistil Interaction in Eucalyptus L'Her. (Myrtaceae): The Effect of Taxonomic Distance

The pollen-pistil interaction was investigated in three intraspecific,57 interspecific and six intergeneric crosses using three speciesof Eucalyptus (Myrtaceae) subgenus Symphyomyrtus, section Bisectariaas female parents Interspecific prefertilization isolation occursin the pistil and manifests as a number of pollen-tube abnormalitiesin the style and ovary associated with a lowered probabilityof ovule penetration The major selection points in the pistilare the upper style and the ovary The seventy of abnormalitiesand the probability of pollen-tube arrest in the pistil wasproportional to the taxonomic distance between parent speciesOvule penetrations were seen mainly in crosses within the sectionBisectaria or between the sections Bisectaria and Adnataria Pollen storage, style length and mean maximum temperature duringthe flowering period of the male parent had no significant effecton pollen-tube growth in the crosses used Mechanisms of reproductiveisolation are discussed in relation to evolutionary relationshipsand the implications for taxonomic groupings Eucalyptus L'Hér, pollen-pistil interaction, incongruity, interspecific hybridization, pollen-tube growth, breeding system, taxonomy     

Ovule and Seed Growth in Pollinated and Auxin-induced Parthenocarpic Watermelon Fruits

Watermelon ovaries of the varieties Early Yates, Sugar Babyand Candy Red were pollinated, stimulated to develop parthenocarpicallywith 0.05, 0.5 or 5 per cent 1-naphthylacetic acid (NAA) inlanolin or treated with lanolin alone (control). Pollinationproduced the greatest number of mature fruits in all varietiesbut the control treatments produced none. Some fruits reachedmaturity in response to all levels of NAA in the varieties EarlyYates and Sugar Baby. Candy Red produced fewer parthenocarpicfruits than Early Yates and Sugar Baby and responded to 0.5and 5 per cent NAA only. Ovule growth was stimulated in allcases except the controls. In Early Yates and Sugar Baby shrinkageand necrosis of ovules was observed at 21 days after treatmentwith 5 per cent NAA. In Candy Red little ovule growth occurredand all parthenocarpic ovules were shrunken and necrotic at21 days after treatment. It is suggested that ovule growth maybe important for early parthenocarpic fruit development. Citrullus lanatus, watermelon, fruit parthenocarpy, ovule, seed growth