The Cape fynbos is characterised by highly leached, sandy, acidic soils with very low nutrient concentrations. Plant-available P levels range from 0.4 μg P g-1 to 3.7 μg P g-I soil, and 1-2 mg N gl soil. Despite the...The Cape fynbos is characterised by highly leached, sandy, acidic soils with very low nutrient concentrations. Plant-available P levels range from 0.4 μg P g-1 to 3.7 μg P g-I soil, and 1-2 mg N gl soil. Despite these low nutrient concentrations, the fynbos is home to 9,030 vascular plant species with 68.7% endemicity. How native plant species survive such low levels of available P is intriguing, and indeed the subject of this review. In the fynbos soils, P is easily precipitated with cations such as Fe and Al, forming AI-P and Fe-P in acidic soils, or Ca-P in neutral-to-alkaline soils. The mechanisms for promoting P availability and enhancing P nutrition include the development of mycorrhizal symbiosis （with 80%-90% of higher plants, e.g., Cyclopia, Aspalathus, Psoralea and Leucadendron etc.） which exhibits 3-5 times much greater P acquisition than non-mycorrhizal roots. Formation of cluster roots by the Leguminosae （Fabaceae） and their exudation of Kreb cycle intermediates （organic acids） for solubilizing P, secretion of root exudate compounds （organic acids, phenolics, amino acids, etc.） that mobilize P. The synthesis and release of acid and alkaline phosphatase enzyme that catalyze the cleavage of mineral P from organic phosphate esters in acidic and alkaline soils, and the development of deep tap roots as well as massive secondary roots within the uppermost 15 cm of soil for capturing water and nutrients. Some fynbos legumes employ all these adaptive mechanisms for enhancing P nutrition and plant growth. Aspalathus and Cyclopia species typically form mycorrhizal and rhizobial symbiosis for improving P and N nutrition, produce cluster roots and acid phosphatases for increasing P supply, and release root exudates that enhance P solubilisation and uptake.展开更多
Aims Cyclopia and Aspalathus are legumes harvested for production of Honeybush and Rooibos tea,respectively.Farmers grow these species from either seeds or cuttings over several years with continuous annual harvesting...Aims Cyclopia and Aspalathus are legumes harvested for production of Honeybush and Rooibos tea,respectively.Farmers grow these species from either seeds or cuttings over several years with continuous annual harvesting.The aims of this study were to assess the effect of plant age,plant species,toposequence,planting material and farmer practice on nitrogen(N)nutrition and water-use efficiency of two Cyclopia and Aspalathus species in the Cape fynbos.Methods The study was conducted using plants from Koksrivier farm located near Gansbaai(33°S 18°E,39 m.a.s.l),and at Kanetberg farm near Barrydale(33°S 21°E,830 m.a.s.l).The 15N natural abundance technique was used to determine N_(2)fixation,carbon(C)assimilation andδ^(13)C in shoot of Cyclopia and Aspalathus species.Important Findings Older tea plantations of C.genistoides and C.subternata derived more N from fixation and exhibited greater water-use efficiency than younger plants.At Koksrivier,Aspalathus caledonensis and A.aspalathoides showed greater water-use efficiency and derived more N from fixation than Cyclopia genistoides.Annual harvesting of C.genistoides decreased N_(2)fixation.At Kanetberg,C.subter-nata plants on the upper and middle slopes derived more N from atmospheric fixation than those on the lower slope.C.subternata plants grown from seedlings recorded greater%Ndfa than cuttings.N_(2)fixation and water-use efficiency of Cyclopia was affected by age,slope and planting material.Further,symbiotic N nutrition and water-use efficiency of Cyclopia and Aspalathus were related.展开更多
Aspalathus linearis is a commercially important plant species endemic to the Cape Floristic Region of South Africa and is used to produce a herbal tea known as rooibos tea.Symbiotic interactions between A.linearis and...Aspalathus linearis is a commercially important plant species endemic to the Cape Floristic Region of South Africa and is used to produce a herbal tea known as rooibos tea.Symbiotic interactions between A.linearis and soil bacteria play an important role in the survival of Aspalathus plants in the highly nutrient-poor,acidic fynbos soil.The aim of this study was to characterize and compare rhizosphere and bulk soil bacterial communities associated with natural and commercially grown A.linearis,as well as the effect of seasonal changes on these communities.Bacterial communities were characterized using high throughput amplicon sequencing,and their correlations with soil chemical properties were investigated.The N-fixing bacterial community was characterized using terminal restriction fragment length polymorphism and real time quantitative polymerase chain reaction.Actinobacteria,Proteobacteria,and Acidobacteria were the most dominant bacterial phyla detected in this study.Highly similar bacterial communities were associated with natural and commercially grown plants.Significant differences in the bacterial community were observed between rhizosphere and bulk soils collected in the dry season,while no significant differences were detected in the wet season.This study provides insights into bacterial community structure and potential factors shaping bacterial community structure with commercially important A.linearis.展开更多
The Southern African biomes are complex biotic communities, with its distinctive plant and animal species, and are maintained under the suitable climatic conditions of the region. It includes the Fynbos Biome and the ...The Southern African biomes are complex biotic communities, with its distinctive plant and animal species, and are maintained under the suitable climatic conditions of the region. It includes the Fynbos Biome and the Succulent Karoo Biome, which forms the smallest of the world’s six Floristic Kingdoms, and they are of conservation concern. The other six biomes are Albany Thicket, Desert, Grassland, Indian Ocean Coastal belt, Nama-Karoo, Savanna. The biomes are not only threatened by agricultural expansion, overgrazing, and mining;but also by future climate changes and droughts. This study investigates the how to best model the possible vulnerable biome areas, under future climate changes, and how Southern African geology plays a huge role in the restriction of the biome shifts. It provides evidence regarding the importance of the study to understanding the climate change impacts and the geological variables on the Southern African biomes, in terms of possible future biome habitat loss.展开更多
Aims The role of tissue acid phosphatase(APase)activity of legumes and non-legumes in their P nutrition and adaptation to low-P soils is not well understood.To better understand this,a relationship between APase activ...Aims The role of tissue acid phosphatase(APase)activity of legumes and non-legumes in their P nutrition and adaptation to low-P soils is not well understood.To better understand this,a relationship between APase activ-ity and P concentration in leaves,stems,roots and nodules of legumes,Cyclopia and Aspalathus and a non-legume,Leucadendron strictum,all native to the P-poor soils of the Cape fynbos biome,was assessed.Methods Plants were collected and each separated into leaves,stems and roots.Phosphatase enzyme activity was assayed in soil using the p-nitrophenol method,while soil P and shoot P were measured using ICP-MS.To measure tissue APase activity,an acetate buffer was added into ground plant material and contents filtered.An ace-tate buffer and a p-nitrophenyl solution were added to the superna-tant and contents incubated.After incubation,NaOH(0.5 M)was added and absorbance read at 405 nm.Important Findings At Koksrivier,Cyclopia genistoides exhibited the highest leaf enzyme activity whilst Aspalathus aspalathoides showed the highest enzyme activity in the stems.At both Kleinberg and Kanetberg,Cyclopia subternata and Cyclopia longifolia showed the highest APase activity in leaves,followed by stems and low-est in roots.P concentration closely mirrored enzyme activity in organs of all test species from each site.APase activity posi-tively correlated with P concentration in organs of all the test Cyclopia and Leucadendron species,indicating that intracellular APase activity is directly linked to P mobilization and transloca-tion in these species.Percentage of N derived from fixation was positively correlated with tissue APase activity in C.genistoides(r=0.911^(*)),A.aspalathoides(r=0.868^(*))and Aspalathus cal-edonensis(r=0.957^(*)),suggesting that APase activity could be directly or indirectly linked to symbiotic functioning in these fynbos legumes,possibly via increased P supply to sites of N2 fixation.展开更多
文摘The Cape fynbos is characterised by highly leached, sandy, acidic soils with very low nutrient concentrations. Plant-available P levels range from 0.4 μg P g-1 to 3.7 μg P g-I soil, and 1-2 mg N gl soil. Despite these low nutrient concentrations, the fynbos is home to 9,030 vascular plant species with 68.7% endemicity. How native plant species survive such low levels of available P is intriguing, and indeed the subject of this review. In the fynbos soils, P is easily precipitated with cations such as Fe and Al, forming AI-P and Fe-P in acidic soils, or Ca-P in neutral-to-alkaline soils. The mechanisms for promoting P availability and enhancing P nutrition include the development of mycorrhizal symbiosis （with 80%-90% of higher plants, e.g., Cyclopia, Aspalathus, Psoralea and Leucadendron etc.） which exhibits 3-5 times much greater P acquisition than non-mycorrhizal roots. Formation of cluster roots by the Leguminosae （Fabaceae） and their exudation of Kreb cycle intermediates （organic acids） for solubilizing P, secretion of root exudate compounds （organic acids, phenolics, amino acids, etc.） that mobilize P. The synthesis and release of acid and alkaline phosphatase enzyme that catalyze the cleavage of mineral P from organic phosphate esters in acidic and alkaline soils, and the development of deep tap roots as well as massive secondary roots within the uppermost 15 cm of soil for capturing water and nutrients. Some fynbos legumes employ all these adaptive mechanisms for enhancing P nutrition and plant growth. Aspalathus and Cyclopia species typically form mycorrhizal and rhizobial symbiosis for improving P and N nutrition, produce cluster roots and acid phosphatases for increasing P supply, and release root exudates that enhance P solubilisation and uptake.
文摘Aims Cyclopia and Aspalathus are legumes harvested for production of Honeybush and Rooibos tea,respectively.Farmers grow these species from either seeds or cuttings over several years with continuous annual harvesting.The aims of this study were to assess the effect of plant age,plant species,toposequence,planting material and farmer practice on nitrogen(N)nutrition and water-use efficiency of two Cyclopia and Aspalathus species in the Cape fynbos.Methods The study was conducted using plants from Koksrivier farm located near Gansbaai(33°S 18°E,39 m.a.s.l),and at Kanetberg farm near Barrydale(33°S 21°E,830 m.a.s.l).The 15N natural abundance technique was used to determine N_(2)fixation,carbon(C)assimilation andδ^(13)C in shoot of Cyclopia and Aspalathus species.Important Findings Older tea plantations of C.genistoides and C.subternata derived more N from fixation and exhibited greater water-use efficiency than younger plants.At Koksrivier,Aspalathus caledonensis and A.aspalathoides showed greater water-use efficiency and derived more N from fixation than Cyclopia genistoides.Annual harvesting of C.genistoides decreased N_(2)fixation.At Kanetberg,C.subter-nata plants on the upper and middle slopes derived more N from atmospheric fixation than those on the lower slope.C.subternata plants grown from seedlings recorded greater%Ndfa than cuttings.N_(2)fixation and water-use efficiency of Cyclopia was affected by age,slope and planting material.Further,symbiotic N nutrition and water-use efficiency of Cyclopia and Aspalathus were related.
基金supported by the National Research Foundation Biodiversity Information Program:Biodiversity Surveys in Priority Inland Areas(FBIP)(South Africa)(No.87602)the National Research Foundation for funding the equipment based at the Central Analytical Facilities of Stellenbosch University,South Africa(No.74452)
文摘Aspalathus linearis is a commercially important plant species endemic to the Cape Floristic Region of South Africa and is used to produce a herbal tea known as rooibos tea.Symbiotic interactions between A.linearis and soil bacteria play an important role in the survival of Aspalathus plants in the highly nutrient-poor,acidic fynbos soil.The aim of this study was to characterize and compare rhizosphere and bulk soil bacterial communities associated with natural and commercially grown A.linearis,as well as the effect of seasonal changes on these communities.Bacterial communities were characterized using high throughput amplicon sequencing,and their correlations with soil chemical properties were investigated.The N-fixing bacterial community was characterized using terminal restriction fragment length polymorphism and real time quantitative polymerase chain reaction.Actinobacteria,Proteobacteria,and Acidobacteria were the most dominant bacterial phyla detected in this study.Highly similar bacterial communities were associated with natural and commercially grown plants.Significant differences in the bacterial community were observed between rhizosphere and bulk soils collected in the dry season,while no significant differences were detected in the wet season.This study provides insights into bacterial community structure and potential factors shaping bacterial community structure with commercially important A.linearis.
文摘The Southern African biomes are complex biotic communities, with its distinctive plant and animal species, and are maintained under the suitable climatic conditions of the region. It includes the Fynbos Biome and the Succulent Karoo Biome, which forms the smallest of the world’s six Floristic Kingdoms, and they are of conservation concern. The other six biomes are Albany Thicket, Desert, Grassland, Indian Ocean Coastal belt, Nama-Karoo, Savanna. The biomes are not only threatened by agricultural expansion, overgrazing, and mining;but also by future climate changes and droughts. This study investigates the how to best model the possible vulnerable biome areas, under future climate changes, and how Southern African geology plays a huge role in the restriction of the biome shifts. It provides evidence regarding the importance of the study to understanding the climate change impacts and the geological variables on the Southern African biomes, in terms of possible future biome habitat loss.
基金The South African Research Chair in Agrochemurgy and PlantSymbioses, the National Research Foundation (No. 47720)theTshwane University of Technology are acknowledged for supportingthe research of F.D.D., and for providing a bursary to S.T.M. Weare grateful to the farmers (Mr Fritz Joubert and Mrs Rica Joubertat Koksrivier, and Mr Matie Taljaard and Mrs Erica Taljaard atKanetberg) for allowing us to collect plant and soil samples from theircommercial Honeybush tea plantations.
文摘Aims The role of tissue acid phosphatase(APase)activity of legumes and non-legumes in their P nutrition and adaptation to low-P soils is not well understood.To better understand this,a relationship between APase activ-ity and P concentration in leaves,stems,roots and nodules of legumes,Cyclopia and Aspalathus and a non-legume,Leucadendron strictum,all native to the P-poor soils of the Cape fynbos biome,was assessed.Methods Plants were collected and each separated into leaves,stems and roots.Phosphatase enzyme activity was assayed in soil using the p-nitrophenol method,while soil P and shoot P were measured using ICP-MS.To measure tissue APase activity,an acetate buffer was added into ground plant material and contents filtered.An ace-tate buffer and a p-nitrophenyl solution were added to the superna-tant and contents incubated.After incubation,NaOH(0.5 M)was added and absorbance read at 405 nm.Important Findings At Koksrivier,Cyclopia genistoides exhibited the highest leaf enzyme activity whilst Aspalathus aspalathoides showed the highest enzyme activity in the stems.At both Kleinberg and Kanetberg,Cyclopia subternata and Cyclopia longifolia showed the highest APase activity in leaves,followed by stems and low-est in roots.P concentration closely mirrored enzyme activity in organs of all test species from each site.APase activity posi-tively correlated with P concentration in organs of all the test Cyclopia and Leucadendron species,indicating that intracellular APase activity is directly linked to P mobilization and transloca-tion in these species.Percentage of N derived from fixation was positively correlated with tissue APase activity in C.genistoides(r=0.911^(*)),A.aspalathoides(r=0.868^(*))and Aspalathus cal-edonensis(r=0.957^(*)),suggesting that APase activity could be directly or indirectly linked to symbiotic functioning in these fynbos legumes,possibly via increased P supply to sites of N2 fixation.
