Kos, Martijn and Poschlod, Peter (2007) Seeds use temperature cues to ensure germination under nurse-plant shade in xeric Kalahari savannah. ANNALS OF BOTANY, 99 (4). pp. 667-675. ISSN 0305-7364,
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Background and Aims In and environments many plant species are found associated with the canopies of woody perennials. Favourable conditions for establishment under canopies are likely to be associated with shade, but under canopies shade is distributed patchily and differs in quality. Diurnal temperature fluctuations and maximum temperatures could be reliable indicators of safe sites. Here, an examination is made as to whether canopy-associated species use temperature cues to germinate in shade patches, rather than matrix areas between trees. Methods The study was carried out in and southern Kalahari savannah (Republic of South Africa). Perennial and annual species associated with Acacia erioloba trees and matrix species were germinated at temperature regimes resembling shaded and unshaded conditions. Soil temperature was measured in the field. Key Results Germination of all fleshy-fruited perennial acacia-associated species and two annual acacia-associated species was inhibited by the temperature regime resembling unshaded conditions compared with at least one of the regimes resembling shaded conditions. Inhibition in perennials decreased with seed mass, probably reflecting that smaller seedlings are more vulnerable to drought. Germination of matrix species was not inhibited by the unshaded temperature regime and in several cases it increased germination compared with shaded temperature regimes or constant temperature. Using phylogenctically independent contrasts a significant positive relationship was found between canopy association and the germination at shade temperatures relative to unshaded temperatures. Conclusions The data support the hypothesis that canopy species have developed mechanisms to prevent germination in open sun conditions. The results and data from the literature show that inhibition of germination at temperature regimes characteristic of open sun conditions can be found in fleshy-fruited species of widely divergent taxonomic groups. It is predicted that germination mechanisms to detect canopy shade based on temperature cues are widespread in species depending on nurse plants, especially bird-dispersed species.
| Item Type: | Article |
|---|---|
| Uncontrolled Keywords: | CACTUS NEOBUXBAUMIA-TETETZO; SEEDLING ESTABLISHMENT; SEMIARID ENVIRONMENT; TEHUACAN VALLEY; PATCH DYNAMICS; ARID SAVANNA; TREES; VEGETATION; SOILS; FACILITATION; directed dispersal; facilitation; nurse plants; germination cue; daily temperature fluctuation; maximum temperature; fleshy-fruited plants; ornithochory; Kalahari; arid environments |
| Subjects: | 500 Science > 580 Botanical sciences |
| Divisions: | Biology, Preclinical Medicine > Institut für Pflanzenwissenschaften > Lehrstuhl für Ökologie und Naturschutzbiologie (Prof. Dr. Peter Poschlod) |
| Depositing User: | Dr. Gernot Deinzer |
| Date Deposited: | 16 Dec 2020 06:14 |
| Last Modified: | 16 Dec 2020 06:14 |
| URI: | https://pred.uni-regensburg.de/id/eprint/32909 |
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