e-journal

Patterns of odour emission, thermogenesis and pollinator activity in cones of an African cycad: what mechanisms apply?

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† Background and Aims:
Ontogenetic patterns of odour emissions and heating associated with plant reproductive structures may have profound effects on insect behaviour, and consequently on pollination. In some cycads, notably Macrozamia, temporal changes in emission of specific odour compounds and temperature have been interpreted as a ‘push–pull’ interaction in which pollinators are either attracted or repelled according to the concentration
of the emitted volatiles. To establish which mechanisms occur in the large Encephalartos cycad clade, the temporal patterns of volatile emissions, heating and pollinator activity of cones of Encephalartos villosus in the Eastern Cape (EC) and KwaZulu Natal (KZN) of South Africa were investigated.

† Methods and Key Results:
Gas chromatography–mass spectrometry (GC-MS) analyses of Encephalartos villosus cone volatiles showed that emissions, dominated by eucalyptol and 2-isopropyl-3-methoxypyrazine in EC populations and (3E)-1,3-octadiene and (3E,5Z)-1,3,5-octatriene in the KZN populations, varied across developmental stages but did not vary significantly on a daily cycle. Heating in male cones was higher at dehiscence than during pre- and post-dehiscence, and reached a maximum at about 1830 h when temperatures were between 7.0 and 12.0 oC above ambient. Daily heating of female cones was less pronounced and reached a maximum at about 1345 h when it was on average between 0.9 and 3.0 oC above ambient. Insect abundance on male cones was higher at dehiscence
than at the other stages and significantly higher in the afternoon than in the morning and evening.

†Conclusions:
There are pronounced developmental changes in volatile emissions and heating in E. villosus cones, as well as strong daily changes in thermogenesis. Daily patterns of volatile emissions and pollinator abundance in E. villosus are different from those observed in some Macrozamia cycads and not consistent with the push–pull
pattern as periods of peak odour emission do not coincide with mass exodus of insects from male cones.

Key words: Encephalartos villosus, Zamiaceae, cycads, monoterpenes, developmental stages, nitrogen-containing
compounds, unsaturated hydrocarbons, gas chromatography–mass spectrometry, push–pull, odour emission, floral
volatiles, thermogensis, pollination.

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Informasi Detail

Judul Seri

Annals of Botany

No. Panggil

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Penerbit

Oxford : Oxford University Press on behalf of the Annals of Botany Company., 2013

Deskripsi Fisik

Annals of Botany 112: 891–902, 2013

Bahasa

English

ISBN/ISSN

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Klasifikasi

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Tipe Isi

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Tipe Media

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Tipe Pembawa

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Edisi

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Subjek

EKOFISIOLOGI TANAMAN

Info Detail Spesifik

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Pernyataan Tanggungjawab

agus

Versi lain/terkait

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