Pollination biology of Bergeranthus multiceps (Aizoaceae) with preliminary observations of repeated flower opening and closure
- Peter, Craig I, Dold, Anthony P, Barker, Nigel P, Ripley, Bradford S
- Authors: Peter, Craig I , Dold, Anthony P , Barker, Nigel P , Ripley, Bradford S
- Date: 2004
- Language: English
- Type: Article
- Identifier: vital:6529 , http://hdl.handle.net/10962/d1005970
- Description: Little is known about pollination of the Aizoaceae (Mesembryanthemaceae). There are sparse reports of generalist pollination in the family by a variety of insects (predominantly bees). Furthermore, most species are self-incompatible in cultivation. In this study, observations were made on two populations of Bergeranthus multiceps (Salm-Dyck) Schwantes growing in the Eastern Cape province of South Africa. Insects visiting the flowers were collected and examined for pollen. While 79 individual insects (in 24 genera representing 14 families and four orders) were collected visiting the flowers, the majority (43 individuals) were female Allodapula variegata bees (Apidae, subfamily Xylocopinae, tribe Allodapini)collecting pollen. All other bee visitors were also female, suggesting pollen collection as the primary activity at the flowers. The protandrous flowers were found to be self-incompatible, pointing to the importance of bee-mediated xenogamy in this species. The flowers of B. multiceps are bright yellow in the human visual spectrum. In addition, the petals of this species reflect ultraviolet light. In contrast, the yellow anthers absorb UV. Flower opening and closing is common in the Aizoaceae. Interestingly, in B. multiceps flowers open at about 15:30 and remain open for approximately three hours before closing again in the late afternoon. These afternoon flower opening events were found to be closely correlated to ambient temperatures above 23°C, relative humidity lower than 50% and vapour pressure deficit below 1.05 kPa measured from as early as 09:00 on the days when flowers opened.
- Full Text:
- Date Issued: 2004
- Authors: Peter, Craig I , Dold, Anthony P , Barker, Nigel P , Ripley, Bradford S
- Date: 2004
- Language: English
- Type: Article
- Identifier: vital:6529 , http://hdl.handle.net/10962/d1005970
- Description: Little is known about pollination of the Aizoaceae (Mesembryanthemaceae). There are sparse reports of generalist pollination in the family by a variety of insects (predominantly bees). Furthermore, most species are self-incompatible in cultivation. In this study, observations were made on two populations of Bergeranthus multiceps (Salm-Dyck) Schwantes growing in the Eastern Cape province of South Africa. Insects visiting the flowers were collected and examined for pollen. While 79 individual insects (in 24 genera representing 14 families and four orders) were collected visiting the flowers, the majority (43 individuals) were female Allodapula variegata bees (Apidae, subfamily Xylocopinae, tribe Allodapini)collecting pollen. All other bee visitors were also female, suggesting pollen collection as the primary activity at the flowers. The protandrous flowers were found to be self-incompatible, pointing to the importance of bee-mediated xenogamy in this species. The flowers of B. multiceps are bright yellow in the human visual spectrum. In addition, the petals of this species reflect ultraviolet light. In contrast, the yellow anthers absorb UV. Flower opening and closing is common in the Aizoaceae. Interestingly, in B. multiceps flowers open at about 15:30 and remain open for approximately three hours before closing again in the late afternoon. These afternoon flower opening events were found to be closely correlated to ambient temperatures above 23°C, relative humidity lower than 50% and vapour pressure deficit below 1.05 kPa measured from as early as 09:00 on the days when flowers opened.
- Full Text:
- Date Issued: 2004
Quantification of the photosynthetic performance of phosphorus-deficient Sorghum by means of chlorophyll-a fluorescence kinetics
- Ripley, Bradford S, Redfern, S P, Dames, Joanna F
- Authors: Ripley, Bradford S , Redfern, S P , Dames, Joanna F
- Date: 2004
- Language: English
- Type: Article
- Identifier: vital:6456 , http://hdl.handle.net/10962/d1004464
- Description: Chlorophyll fluorescence induction curves have been used as a sensitive tool for screening the photosynthetic performance of plants. Experimental treatments involving nitrate supply and chilling stress have been shown to affect fluorescence induction curves and other measures of photosynthesis. We have investigated the photosynthetic performance of Sorghum bicolor supplied with Long Ashton growth solution containing standard (20 μmol mol^(–1)) or low (5 μmol mol^(–1)) phosphorus. The JIP-test based on the chlorophyll fluorescence induction curve was used as a non-destructive method to measure the relative proportions of energy dissipated by different processes (termed energy fluxes) in the light reactions. The various energy fluxes or derived parameters were compared to find the measures that were most sensitive to the experimental conditions. Plant response to treatments was first evident in selected chlorophyll fluorescence parameters, particularly performance index (PI_ABS_); plants with increased PI_ABS_ manifested higher electron transport activity and dissipated less energy as heat, possibly as a result of their better phosphorus status, leading to more functional reaction centres. Observed changes in fluorescence were correlated to changes in gas exchange and biomass. Standard phosphorus treatments significantly increased biomass, leaf area, photosynthetic and respiratory rates, carboxylation efficiencies and levels of ribulose biphosphate regeneration rates, relative to plants with low supplies of nutrients.
- Full Text:
- Date Issued: 2004
- Authors: Ripley, Bradford S , Redfern, S P , Dames, Joanna F
- Date: 2004
- Language: English
- Type: Article
- Identifier: vital:6456 , http://hdl.handle.net/10962/d1004464
- Description: Chlorophyll fluorescence induction curves have been used as a sensitive tool for screening the photosynthetic performance of plants. Experimental treatments involving nitrate supply and chilling stress have been shown to affect fluorescence induction curves and other measures of photosynthesis. We have investigated the photosynthetic performance of Sorghum bicolor supplied with Long Ashton growth solution containing standard (20 μmol mol^(–1)) or low (5 μmol mol^(–1)) phosphorus. The JIP-test based on the chlorophyll fluorescence induction curve was used as a non-destructive method to measure the relative proportions of energy dissipated by different processes (termed energy fluxes) in the light reactions. The various energy fluxes or derived parameters were compared to find the measures that were most sensitive to the experimental conditions. Plant response to treatments was first evident in selected chlorophyll fluorescence parameters, particularly performance index (PI_ABS_); plants with increased PI_ABS_ manifested higher electron transport activity and dissipated less energy as heat, possibly as a result of their better phosphorus status, leading to more functional reaction centres. Observed changes in fluorescence were correlated to changes in gas exchange and biomass. Standard phosphorus treatments significantly increased biomass, leaf area, photosynthetic and respiratory rates, carboxylation efficiencies and levels of ribulose biphosphate regeneration rates, relative to plants with low supplies of nutrients.
- Full Text:
- Date Issued: 2004
- «
- ‹
- 1
- ›
- »