Growth response of three globose cacti to radiation and soil moisture: an experimental test of the mechanism behind the nurse effect
Cactus seedlings often establish under nurse plants which modify environmental conditions by increasing moisture and decreasing solar radiation, which may cause beneficial and detrimental effects, respectively, on seedling growth. Three soil moisture treatments (5%, 25% and 60%) and two solar radiat...
| Authors: | , |
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| Format: | article |
| Status: | Published version |
| Publication Date: | 2008 |
| Country: | México |
| Institution: | Universidad Nacional Autónoma de México |
| Repository: | Sistema de Información de la Facultad de Ciencias, UNAM |
| OAI Identifier: | oai:repositorio.fciencias.unam.mx:11154/141159 |
| Online Access: | http://hdl.handle.net/11154/141159 |
| Access Level: | Open access |
| Keyword: | Biomass allocation Growth analysis Phenotypic plasticity Rare species Seedling establishment |
| Summary: | Cactus seedlings often establish under nurse plants which modify environmental conditions by increasing moisture and decreasing solar radiation, which may cause beneficial and detrimental effects, respectively, on seedling growth. Three soil moisture treatments (5%, 25% and 60%) and two solar radiation levels (100% exposure=243 ?mol m?2 s?1, and 40%=102 ?mol m?2 s?1) were used in a factorial design to analyze seedling growth response of three rare cactus species (Mammillaria pectinifera, Obregonia denegrii and Coryphantha werdermannii). The variables evaluated were relative growth rate (RGR), root/shoot ratio (R/S), and K (RGRroots/RGRshoot), obtained from an initial seedling harvest (6-month-old seedlings) and a final harvest 6 months after treatment application. All three species had slow RGRs (0.002–0.012 g g?1 day?1). O. denegrii had the lowest RGR values, but was the only species for which R/S and K varied with soil moisture. While all seedlings responded markedly to soil moisture, no response was observed to radiation treatments. The latter might have been related to the relatively low solar radiation levels present in the greenhouse. Yet, our results suggest that the main benefit nurse plants offer to seedlings is the increase in soil moisture. |
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