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Multiple factors contribute to outcrossing in a tropical emergent Dipterocarpus tempehes, including a new pollen-tube guidance mechanism for self-incompatibility


Kenta, Tanaka; Shimizu, Kentaro K; Nakagawa, Michiko; Okada, Kiyotaka; Hamid, Abang A; Nakashizuka, Tohru (2002). Multiple factors contribute to outcrossing in a tropical emergent Dipterocarpus tempehes, including a new pollen-tube guidance mechanism for self-incompatibility. American Journal of Botany, 89(1):60-66.

Abstract

The self-rejection system of Dipterocarpus tempehes (Dipterocarpaceae), an emergent tree of the lowland tropical forests of Borneo, were studied by means of pollination experiments, fluorescence microscopy of pollen tubes, and monitoring of ovary maturation patterns. Fruit set was higher in cross-pollinated flowers than in control and self-pollinated flowers, indicating the existence of pollen limitation and a self-rejection system. Although the adhesion and the germination of self-pollen and the growth of self-pollen tubes were not inhibited, the proportion of cross-pollen tubes that entered the style was 1.7–2.3 times higher than that of self-pollen tubes, indicating a partial self-incompatibility that inhibits self-pollen tubes from entering the style hollow. These results suggest, for the first time, that self-incompatibility is caused by a defect of pollen-tube guidance. We also suggest a threshold effect in number of pollen tubes or late-acting self-incompatibility to fully explain the drastic and uniform selection against self-pollinated flowers before ovary swelling. After that, maternal selection and/or inbreeding depression caused the abortion and delayed maturation of self-pollinated flowers. The advantages of the self-rejection process composed of partial early-acting self-incompatibility and relatively strong delayed abortion is discussed with respect to the general-flowering phenomenon in lowland dipterocarp forests.

Abstract

The self-rejection system of Dipterocarpus tempehes (Dipterocarpaceae), an emergent tree of the lowland tropical forests of Borneo, were studied by means of pollination experiments, fluorescence microscopy of pollen tubes, and monitoring of ovary maturation patterns. Fruit set was higher in cross-pollinated flowers than in control and self-pollinated flowers, indicating the existence of pollen limitation and a self-rejection system. Although the adhesion and the germination of self-pollen and the growth of self-pollen tubes were not inhibited, the proportion of cross-pollen tubes that entered the style was 1.7–2.3 times higher than that of self-pollen tubes, indicating a partial self-incompatibility that inhibits self-pollen tubes from entering the style hollow. These results suggest, for the first time, that self-incompatibility is caused by a defect of pollen-tube guidance. We also suggest a threshold effect in number of pollen tubes or late-acting self-incompatibility to fully explain the drastic and uniform selection against self-pollinated flowers before ovary swelling. After that, maternal selection and/or inbreeding depression caused the abortion and delayed maturation of self-pollinated flowers. The advantages of the self-rejection process composed of partial early-acting self-incompatibility and relatively strong delayed abortion is discussed with respect to the general-flowering phenomenon in lowland dipterocarp forests.

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Additional indexing

Item Type:Journal Article, refereed, original work
Communities & Collections:07 Faculty of Science > Department of Plant and Microbial Biology
07 Faculty of Science > Institute of Evolutionary Biology and Environmental Studies
Dewey Decimal Classification:570 Life sciences; biology
590 Animals (Zoology)
580 Plants (Botany)
Uncontrolled Keywords: breeding system canopy access Dipterocarpaceae inbreeding depression Lambir Hills National Park pollination experiment pollen-tube guidance self-incompatibility
Language:English
Date:2002
Deposited On:19 Feb 2013 08:24
Last Modified:26 Oct 2017 14:29
Publisher:Botanical Society of America
ISSN:0002-9122
Free access at:Publisher DOI. An embargo period may apply.
Publisher DOI:https://doi.org/10.3732/ajb.89.1.60
PubMed ID:21669712

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