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Interrogative proteome analyses are used to identify and quantify the expression of proteins involved in heat tolerance and to identify associated physiological processes in heat-stressed plants. The objectives of the study were to identify and quantify the expression of proteins involved in heat tolerance and to identify associated physiological processes in chickpea (Cicer arietinum L.) heat-tolerant (Acc#7) and sensitive genotype (Acc#8) from a field study. Proteomic and gene ontological analyses showed an upregulation in proteins related to protein synthesis, intracellular traffic, defence and transport in the heat-tolerant genotype compared to the susceptible one at the warmer site. Results from KEGG analyses indicate the involvement of probable sucrose-phosphate synthase (EC 2.4.1.14) and sucrose-phosphate phosphatase (EC 3.1.3.24) proteins, that were upregulated in the heat-tolerant genotype at the warmer site, in the starch and sucrose pathway. The presence of these differentially regulated proteins including HSP70, ribulose bisphosphate carboxylase/oxygenase activase, plastocyanin and protoporphyrinogen oxidase suggests their potential role in heat tolerance, at flowering growth stage, in field-grown chickpea. This observation supports unaltered physiological and biochemical performance of the heat-tolerant genotypes (Acc#7) relative to the susceptible genotype (Acc#8) in related studies (Makonya et al. 2019). Characterisation of the candidate proteins identified in the current study as well as their specific roles in the tolerance to heat stress in chickpea are integral to further crop improvement initiatives.

Calobota sericea is a native legume of South Africa, confined to the water-limited rangelands, and it has recently been prioritised for additional characterisation regarding its pasture potential. ...

Fabaceae plants contribute greatly to a high quality of pasture in rangelands, because of high levels of protein in their tissues. Despite this established importance, only a few southern African legumes have been evaluated for nutritional value and domestication. The Overberg renosterveld vegetation of the Fynbos biome occupies undulating landscapes that have multiple slope aspects, creating variable microclimatic conditions affecting nutrient dynamics, species richness and plant chemical compositions. We assessed the effect of slope aspect on fiber and mineral composition of forage species present to provide information on the importance of slope for species characterization and nutritional value for domestication. Tissue samples from six replicates of the same species occurring on opposing aspects were collected for nutritional assessment. Results on the data showed that fibre and mineral composition differed in species occurring on different slopes, albeit with few exceptions. The concentrations of P, K and Mg in some species were significantly higher on the cooler and wetter south facing slopes relative to north facing slopes. Nutrient elements in soil samples collected from each site varied with slope aspects and elements. It is recommended that topography should be considered when studying forage nutritional assessments as part of future domestication programs.

In recent decades climate change has impacted ecosystems negatively globally with Mediterranean systems being particularly vulnerable. Changes in rainfall pattern and amounts have led to increases in flooding and droughts in certain areas of the world. Many important agricultural crops such as Aspalathus linearis (Burm.f.) R. Dahlgren, rooibos tea, rely on the Mediterranean-type seasonality in the Western Cape, South Africa. Aspalathus linearis plants, which occur naturally in the Cedarberg, grow in hot and dry summer conditions and have a root that penetrates the soil down to 2 m, yet no work has looked at the root response to drought under low rainfall environments. The objective of this study was to determine the physiological and morphological response of A. linearis plants grown at two different water regimes to drought. A potted glasshouse experiment was carried out where drought stress (withdrawing watering) was imposed on well-watered and low moisture supplied plants. The low moisture droughted plants exhibited drought tolerant mechanisms which included higher root/shoot ratios as well as thinner roots, both of which are effective for water and nutrient uptake. Overall, plants in the 30% FC treatment recorded lower Pmax, gs and E after three days in the drought conditions while 70% FC plants were only affected after five days. Furthermore, plants grown under low moisture conditions produced 50% lower biomass compared to plants grown under adequate moisture conditions. This implies that low rainfall and the occurrences of dry spells and drought, associated with climate change are likely to reduce the production of A. linearis in the Cederberg area.

The South African Fynbos is the smallest floristic kingdom with high levels of endemism and where fire dominates the landscape. However, drivers of soil microbial distribution and diversity are sti...

Calobota sericea is a perennial legume species from South Africa that has the potential to be implemented as a fodder crop in water-limited agro-ecosystems. Apart from dormancy breaking requirements, no information regarding the germination and seedling establishment requirements of C. sericea is currently available. Therefore, the aim of this study was to determine the germination and establishment abilities of C. sericea at different temperatures, water potentials and seed burial depths. In the first trial seeds were incubated at constant temperatures of 5–30 °C at 5 °C increments and in the second trial, seeds were incubated at 20 °C, at water potentials ranging from 0 to − 1.0 MPa. The seedling emergence trial consisted of a complete randomised block greenhouse trial where seeds were sown at five burial depths (1–5 cm). Seeds were found to germinate best at temperatures ranging between 10 and 20 °C, but still had a germination percentage greater than 80% at 5 °C. The C. sericea seeds were also found to require a water potential of at least – 0.3 MPa to reach a germination potential of 60%, below which germination was severely impacted. Seedling emergence was found to be highest at burial depths of 2–4 cm. After establishment, seedlings generally displayed a decrease in above ground plant part height with increasing burial depth, but an increase in seedling mass. More resources, in terms of mass, were allocated to early root development as opposed to leaves and stems. Results from the current study therefore suggests that C. sericea seeds can be planted between 2 and 3 cm deep, during winter season, when temperatures are lower, and rainfall more prevalent and less erratic.

Heat and drought stresses are two abiotic factors that often occur simultaneouslyand are predicted to increase, consequently hampering plant growth. Responseof different species to either stresses is well documented but information on theresponse of the same genotypes to both stresses in chickpea (Cicer arietinum L.)is limited.We aimed to determine whether previously noted heat-stress-tolerantgenotype (Acc#7) is drought tolerant, that heat-sensitive genotype (Acc#8) isdrought sensitive, and whether intermittent moisture supply at vegetative stagewould induce priming effect to later drought at flowering. At vegetative stage,plants were divided into three groups, nonstressed (watered to 75% field capacity[FC], severe water stress (moisture withholding for 14 d), and treated to 40% FCthroughout the experiment (mild stress), with recovery for the severely stressedplants after which they were stressed (double stress) at flowering. Drought treatmentsat vegetative and flowering growth stages decreased physiological parametersand biomass accumulation in both genotypes except low water supply at40% FC that decreased biomass in Acc#7 but not Acc#8. Double-drought stressresulted in priming effect in Acc#7, having higher biomass, chlorophyll fluorescence,stomatal conductance (gs), net photosynthesis, and relative water content(RWC) vs. the introduction of stress only at flowering growth stage as well asin comparison with Acc#8. These results showed that both Acc#7 and Acc#8 aresensitive to drought, whereas after priming,Acc#7 is better acclimated to droughtthan Acc#8 associated with osmotic adjustment on leaf RWC and higher capacityto protect photosynthetic activity, making Acc#7 potentially ideal for areasassociated with intermittent drought spells.

Vigna unguiculata (L.) Walp. (cowpea), Glycine max (L.) Merr (soybean) and Phaseolus vulgaris (L.) (common bean) plants were exposed to UV-B radiation at above- and below-ambient levels, and their effects on growth, symbiotic performance and root concentration of metabolites were assessed. Moderately and highly elevated UV-B exposures averaging 32 and 62% above ambient had no effect on plant total dry matter, nodule number, nodule mass, nodule size, N fixed or root concentration of flavonoids, anthocyanins, soluble sugars and starch in the three species studied. However, N concentrations were markedly reduced in roots of G. max and P.��vulgaris, and in leaves of P. vulgaris, which contrasted with the significant increase in stems and leaves of V.�unguiculata. Below-ambient UV-B exposures averaging 22% of ambient also altered growth and metabolism of these legumes. Total plant dry matter, nodule number, nodule dry mass, N fixed and root starch concentrations in V.�unguiculata decreased relative to both visible and UV-A radiation controls, whereas in G. max and P. vulgaris, these parameters were not altered. Root concentrations of flavonoids and anthocyanins in all species tested were also unchanged with below-ambient UV-B exposures. Taken together, growth and symbiotic function of these species remained unaltered with exposure to above-ambient UV-B, but differed in their response to below-ambient UV-B radiation.

Interrogative proteome analyses are used to identify and quantify the expression of proteins involved in heat tolerance and to identify associated physiological processes in heat-stressed plants. The objectives of the study were to identify and quantify the expression of proteins involved in heat tolerance and to identify associated physiological processes in chickpea (Cicer arietinum L.) heat-tolerant (Acc#7) and sensitive genotype (Acc#8) from a field study. Proteomic and gene ontological analyses showed an upregulation in proteins related to protein synthesis, intracellular traffic, defence and transport in the heat-tolerant genotype compared to the susceptible one at the warmer site. Results from KEGG analyses indicate the involvement of probable sucrose-phosphate synthase (EC 2.4.1.14) and sucrose-phosphate phosphatase (EC 3.1.3.24) proteins, that were upregulated in the heat-tolerant genotype at the warmer site, in the starch and sucrose pathway. The presence of these differentially regulated proteins including HSP70, ribulose bisphosphate carboxylase/oxygenase activase, plastocyanin and protoporphyrinogen oxidase suggests their potential role in heat tolerance, at flowering growth stage, in field-grown chickpea. This observation supports unaltered physiological and biochemical performance of the heat-tolerant genotypes (Acc#7) relative to the susceptible genotype (Acc#8) in related studies (Makonya et al. 2019). Characterisation of the candidate proteins identified in the current study as well as their specific roles in the tolerance to heat stress in chickpea are integral to further crop improvement initiatives.

This study determined the extent of horizontal gene transfer among rhizobial genera in the Core Cape Subregion (CCR) of South Africa and reconstructed the ancestral symbionts of the legumes. Phylogenies of two chromosomal genes (16S rRNA and recA) and one nodulation gene (nodA) of rhizobia, isolated from diverse legumes in the CCR, were reconstructed using Bayesian and Maximum Likelihood techniques. A cophylogenetic analysis was used to test for congruence between the chromosomal and the nodA phylogenies. Five genera of rhizobia (Bradyrhizobium, Burkholderia, Mesorhizobium, Rhizobium and Sinorhizobium) were studied. A phylogeny of the legumes was reconstructed from matK and rbcL DNA sequences and it was used to reconstruct their ancestral rhizobia, using Bayesian methods. The chromosomal phylogeny of the rhizobia was mostly incongruent with that of nodA, indicating potential horizontal inheritance of the latter. The nodA genes of Burkholderia, Mesorhizobium and Rhizobium had different evolutionary histories from their counterparts in other parts of the globe. Burkholderia was reconstructed as the ancestral symbionts of the CCR legumes. Evidence of co-diversification between the legumes and their symbionts was observed and this highlights a potential role of the legume-rhizobia interaction to the high diversity of legumes in the CCR. Finally, the availability of compatible rhizobia and their competitive ability are discussed as possible drivers for the lack of shared legumes between the Fynbos biome and the Kwongan of Australia.

Introgression is interesting for plant evolutionary studies because it yields significant numbers of new genotypes, thus increasing genetic diversity, but also blurs species boundaries. Here we report a case of introgressive hybridization from a hybrid zone on the Swartberg Pass in the species rich Core Cape Subregion of South Africa. We analysed morphological data from 52 individuals between the hybridizing species Psoralea sp. 15 (P. “forbesiae” sp. nov. ined) and P. sordida C.H. Stirt and Muasya. The data were examined using the Andersonian hybrid index method and multivariate analyses. The results showed that P. “forbesiae” and P. sordida were distinct species linked through a range of intermediates and introgressants to both species and that the sampled populations comprised an introgressive hybrid swarm. Habitat disturbance via road-building has played an important role in the formation and maintenance of the swarm. While introgressive hybridization can increase genetic diversity in the short term in Psoralea it is unclear as to the future of the genetic integrity of the parent species and hybrid populations given the current differences in habitat specialisation (i.e. natural and disturbed habitats, respectively).

Wiborgia Thunb. is a legume genus comprising ten species endemic to the Greater Cape Floristic Region of South Africa. Species in the genus are shrubs of 0.5–3.0 m in height, with distinct ascending to erect habits and shoots terminating in rigid thorns, and are distinguished from other Crotalarieae by their indehiscent one-seeded fruits. The genus Wiborgia was revised by Dahlgren four decades ago. And to date, phylogenetic relationships within the genus are partially known, through studies that inferred phylogenetic relationships using two DNA markers and included seven out of ten Wiborgia species which provided unresolved species relationships. Therefore, this study aimed to further explore relationships within the genus using five fast-evolving DNA markers and sampling multiple accessions to represent morphological and ecological variability, enabling testing hypotheses on the utility of Dahlgren's key morphological characters and support for infrageneric classification. Phylogenetic relationships in Wiborgia were inferred using multiple molecular markers (ITS, rpl32-trnL, rps16, trnS-trnG, and trnT-trnL) and the data were analysed using model based approaches (Maximum Likelihood, Bayesian Inference), with key morphological characters reconstructed using Maximum Likelihood. Within the Wiborgia clade, two strongly supported clades were observed. In Clade 1, a novel, well-supported sister relationship between the widely-distributed W. mucronata and the narrowly distributed W. tenuifolia was observed, both characterized by thorny glabrous branches. In Clade 2, W. tetraptera was identified to be sister to W. fusca, whilst W. monoptera and W. incurvata formed part of a strongly supported clade. Wiborgia obcordata, the only species in Dahlgren's subgenus Wiborgia, was found to be embedded within subgenus Pterocarpia thus the subgeneric classification of Dahlgren was not supported. Key morphological characters (including inflated/compressed fruit walls, the presence of lateral wings, and the presence of thorns) were identified to derive independently across the phylogeny, and thus unsuitable to delineate subgenera. Our reconstructions have shown that these characters, together with other important characters such as branch pubescence and flower colour, could be used in delineating species. Sister pairs (W. incurvata and W. monoptera; W. tenuifolia and W. mucronata) overlap geographically but in most cases showed differences in floral characters (i.e. colour, morphology).

Native forages have been proposed as a plausible alternative to the use of exotic forage germplasm due to their adaptation to the surrounding bioclimatic and edaphic conditions, and the reduced risk of becoming weedy or invasive. Calobota sericea and Lessertia frutescens are two perennial legume species from the semi-arid rangelands of Namaqualand and are currently under investigation as fodder crops for use within these agro-ecosystems. These species display physical seed dormancy, and therefore, we aimed to investigate methods to break their dormancy to ensure fast and uniform seed germination and establishment. After collection, C. sericea and L. frutescens seeds were subjected to three dormancy breaking treatments, namely, mechanical scarification, boiling the seeds for 5 min, and placing the seeds in boiled water and leaving them until the water has cooled to room temperature. The seeds were thereafter germinated in petri-dishes. Mechanical scarification was the most effective method to break dormancy, and once the dormancy was removed, germination commenced rapidly. However, further research is needed to determine more efficient means to scarifying larger quantities of seeds.

Ambiguous species delimitations and nomenclature are a major impediment for users of biodiversity information. This is more pronounced in plant lineages that have experienced recent and rapid diversification or where there is a tendency to lump many species under a general name. The papilionoid genus Psoralea L. is a young lineage (Pliocene, ca. 75 species) which has diversified rapidly within the South African fynbos biome and adjacent habitats. All species bearing 5–19 foliolate leaves were previously often lumped within the polymorphic species Psoralea pinnata, resulting in an unwieldy complex of at least 28 taxa, of which only eleven species are formally named. In this study we analyzed live specimens and populations in the field and herbarium collections, capturing their morphological and geographic diversity, for species delimitation. The results support the recognition of 25 distinct species, of which 14 are described here as new: P. azuroides; P. brilliantissima; P. elegans; P. floccosa; P. imminens; P. intonsa; P. ivumba; P. kougaensis; P. montana; P. muirii; P. rhizotoma; P. semota; P. sordida; and P. suaveolens. The taxon P. pinnata var. latifolia Harv. is raised to species rank, as P. latifolia comb. nov. The name P. pinnata sensu stricto is restricted here to a taxon with 5–9-leaflets extending from the Cape Peninsula to the Kogelberg mountains. We provide a key for the identification of all 25 species along with full descriptions, distribution maps and notes on their conservation status.

Chickpea (Cicer arietinum L.), a cool season crop is severely affected by heat stress, predicted to increase due to warming climates. Research for identifying heat tolerance markers for potential chickpea genotype selection is imperative. The study assessed the response of four chickpea genotypes to a natural temperature gradient in the field using chlorophyll fluorescence, non-structural carbohydrate, chlorophyll concentrations, gas exchange and grain yield. Field experiments were carried out in two winter seasons at three locations with known differences in temperature in NE South Africa. Results showed two genotypes were tolerant to heat stress with an Fv/Fm of 0.83–0.85 at the warmer site, while the two sensitive genotypes showed lower Fv/Fm of 0.78–0.80. Both dark-adapted Fv/Fm and Fq'/Fm' (where Fq' = Fm' –F)measured at comparable high light levels correlated positively with grain yield. The two tolerant genotypes also showed higher photosynthetic rates, starch, sucrose and grain yield than the sensitive genotypes at the warmer site. However, these parameters were consistently higher at the cooler sites than at the warmer. These results were further validated by a climate chamber experiment, where higher Fv/Fm decline in the sensitive compared to tolerant genotypes was observed when they were exposed to short-term heat treatments of 30/25 °C and 35/30 °C. Tolerant genotypes had higher Fv/Fm (0.78–0.81)and grain yield plant−1(1.12–2.37g)compared to sensitive genotypes (0.74–0.75)and (0.32–0.89g plant−1)respectively in the 35/30 °C. It is concluded that chlorophyll fluorescence and leaf carbohydrates are suitable tools for selection of heat tolerant chickpea genotypes under field conditions, while the coolest site showed favourable conditions for chickpea production.

International audience; In many ecosystems, the factors that determine landscape-scale community structure of soil nematodes are poorly understood. We were interested in discovering whether deterministic or stochastic factors dominate nematode community variation. We used a novel metagenetic approach to investigate variation in nematode community structure in the Fynbos vegetation of South Africa. We compared 23 samples of soil nematode communities from five different Fynbos landscapes. Nematode DNA was 454-pyrosequenced for the 18S rRNA gene. We investigated the community structure, diversity, and the relative role of both deterministic (niche-based) and neutral processes may play in delimiting the nematode phylogenetic community structure in different Fynbos vegetation types. Nematode diversity showed no relationship to any measured soil parameter. The phylogenetic signal showed that more closely related types of nematodes in the Fynbos tended to co-occur more often than would be expected by chance, demonstrating that (a) closely related lineages occupy similar niches spatially and (b) community variation is influenced more by determinism than stochasticity. The standardised beta mean nearest taxon distance (ses.βMNTD) index showed no association with vegetation type. Both ses.NTI (nearest taxon index) and ses.βMNTD deviated significantly from null models, indicating that deterministic processes were important in the assembly of nematode communities. Furthermore, at local scale, the ses.NTI was significantly higher than null expectations, indicating that co-occurrence of related nematode lineages is determined by the differences in environmental conditions across the sites. We conclude that in the Fynbos there is niche overlap between closely related types of nematodes, that nematode speciation tends to occur conservatively into closely related niches, and that the phylogenetic community structure reveals that deterministic (rather than stochastic) processes are more important in delimiting the community assembly.

Many legume species in the Cape Floristic Region, recently renamed the Core Cape Subregion (CCR), occur in distinct population patches within the landscape. We hypothesized that when compared to non-legumes, legumes occupy a distinct nutrient-enriched biogeochemical niche, and that foliar nutrient concentrations would correspond with soil chemistry. Soil and leaf samples were collected at eight sites in the CCR that were selected based on soil types including limestone-, sandstone-, granite- and sand-derived soils. At each site, samples were collected along three parallel replicate line transects originating inside the legume patch and extending into the adjacent non-legume habitat. The soil and plant samples were processed and analysed for chemical elements. Within a soil type, canonical discriminant analysis of soil nutrient concentrations separated legume from non-legume habitats on limestone, sandstone and granitic soils, thereby identifying their biogeochemical niche. Multiple nutrients were associated with the legume niche, and the nutrients varied with soil type. Relative to the non-legume habitat, the legume habitat was enriched with nutrients with greater concentrations of total N, total P, K, Mg, Na and C in both limestone and sandstone soils, but only enriched with C in granitic soil. Furthermore, a strong canonical correlation in both legume and non-legume plants (e.g. along CV1 r = 0.90 and 0.83, respectively) was found between the soil and leaf nutrients. Overall, the study provided empirical evidence for the existence of a nutrient-rich biogeochemical niche for legumes in the CCR and showed that foliar nutrients reflected soil chemistry.

Mediterranean systems, such as in South Africa, are particularly vulnerable to the predicted increases in mean surface temperatures which will likely affect the growth and physiology of many plants and subsequently affect agricultural productivity. Aspalathus linearis (Burm.f.) R. Dahlgren (rooibos) is an important commercial, endemic crop that is produced in the Cederberg region, South Africa. This region experiences a Mediterranean-type ecosystem that is characterised by hot, dry summers (November – February) and cool, wet winters (May – August). This study assessed the effects of temperature on the growth and stress tolerant traits of A. linearis over two years. Crop biomass and selected physiological traits were determined in the field, along a temperature gradient, at four farm sites in the Cederberg during the summer and winter 2017 and summer 2018. Aspalathus linearis plants showed evidence of transpirational leaf cooling during summer and this, combined with lower chlorophyll and high phenolic content, could be considered acclimatized adaptive changes allowing the plants to mitigate the heating effects of elevated temperatures. Although changes in soil nutrients and increasing temperatures had a negative impact on crop biomass, the phenolic content, a measure of tea quality, did not vary with sites. This suggests that a shift in rooibos farming to cooler and wetter areas further south, for better growth and higher yields, would not compromise the quality of rooibos tea.

The limited grazeable size of renosterveld vegetation in the Western Cape warranted assessment of chemical and fibre composition of the species to determine their nutritive value. We hypothesised that Fabaceae has chemically superior palatable species relative to Poaceae, Asteraceae and Asparagaceae species in the area. Plant samples were collected in the Overberg region from 11 sites. The species sampled from these four families Fabaceae, Poaceae, Asteraceae, and Asparagaceae were analysed for macro- and micro-elements, fibre and secondary compounds. At each site, replicated soil samples were also collected and analysed for pH, macro- and micro-elements. Fabaceae recorded the greatest concentration of crude protein, but the Poaceae was the most fibrous relative to Fabaceae and Asteraceae. All the species contained adequate levels of nutrients except P, Zn and sometimes Cu. Soil concentration of macronutrients and carbon in the soil varied with location. Based on crude protein, neutral detergent fibre and digestibility, the three most important parameters defining forage quality, the Fabaceae species Aspalathus hispida, A. angustifolia, A. nigra and A. submissa were regarded as superior forage species in the Mediterranean renosterveld. Livestock relying on only the renosterveld species in the Western Cape as forages should receive P and Zn supplements.

The genus Psoralea L., comprising about 70 species, has its centre of diversity and endemism in the Greater Cape Floristic Region of South Africa. Species delimitation and identification in the genus are difficult. Many putative species are unpublished or known only by manuscript names. As a first step to address this problem this study reports on the taxonomy of the Psoralea aphylla complex — a distinct group of species characterised by either a complete absence of leaves, a reduction of the leaves into scales, or the occurrence of small filiform leaflets. Plants may be suffrutices, small to large shrubs, or trees. Morphological and ecological analyses of herbarium specimens and recent field collections distinguished ten species within the complex. Three species (P. aphylla L., P. filifolia Eckl. & Zeyh. and P. peratica C.H.Stirt.) are already published, while the seven other taxa have been known by manuscript names and are formalised in this paper (P. congesta C.H.Stirt. & Muasya; P. fleta C.H.Stirt.; P. gigantea Dludlu, Muasya & C.H.Stirt.; P. pullata C.H.Stirt.; P. ramulosa C.H.Stirt.; P. rigidula C.H.Stirt.; and P. usitata C.H.Stirt.). We provide a key for the identification of all ten species along with full descriptions, illustrations, distribution maps and some notes on the conservation statuses of the species.

Podalyria calyptrata is from fynbos soils with low availability of phosphorus (P) and nitrogen (N). We investigated the physiological basis for tolerance of low P supply in nodulated P. calyptrata and examined responses to increased supply of combined-N as Ca(NO3)2 and P. It was hypothesized that increasing supply of combined-N would stimulate P-acquisition mechanisms and enhance plant growth with high P supply. Biomass, leaf [N] and [P], organic acid and phosphatase root exudates, and phosphoenolpyruvate carboxylase (PEPC) and malate dehydrogenase (MDH) activity in nodules and roots were examined in two N×P experiments. Low P supply decreased leaf [P] and limited growth, decreasing the nodule:root ratio but increasing nodular PEPC and MDH activity for enhanced P-acquisition or P-utilization. At low P supply, a N-induced demand for P increased root exudation of citrate and PEPC and MDH activity in roots. Greater combined-N supply inhibited nodulation more at low P supply than at high P supply. With a P-induced demand for N the plants nodulated prolifically and increased combined-N supply did not enhance plant growth. The physiological basis for N2-fixing P. calyptrata tolerating growth at low P supply and responding to greater P supply is through balanced acquisition of P and N for plant demand.

In the face of climate change, identification of forage species suitable for dryland farming under low rainfall conditions in South Africa is needed. Currently, there are only a limited number of forage species suitable for dryland farming under such conditions. The objective of this study was to identify and prioritise native legume species that could potentially be used in dryland farming systems in water-limited agro-ecosystems in South Africa. Using a combination of ecological niche modelling techniques, plant functional traits, and indigenous knowledge, 18 perennial herbaceous or stem-woody legume species were prioritised for further evaluation as potential fodder species within water-limited agricultural areas. These species will be evaluated further for their forage quality and their ability to survive and produce enough biomass under water limitation and poor edaphic conditions.

Aims: To evaluate the effect of planting density and cropping systems on the changes in rhizosphere concentration and uptake of mineral elements of five cowpea genotypes (i.e. Bensogla, ITH98-46, Sanzie, TVu1509 and Omondaw). Study Design: 3-factorial randomized complete block design. Original Research Article American Journal of Experimental Agriculture, 4(2): 193-214, 2014 194 Place and Duration of Study: Nietvoorbij (33o54S, 18o14E), Stellenbosch, South Africa during 2005 and 2006 summer seasons. Methodology: A field experiment involving two cowpea plant densities (83,333 and 166,666 plants.ha), two cropping systems (monocropping and intercropping) and five cowpea genotypes (i.e. Bensogla, ITH98-46, Sanzie, TVu1509 and Omondaw). Results: The data for 2005 and 2006 were similar, and therefore pooled for statistical analysis. The concentrations of P, K, S, Na, Cu, and Zn were lower in rhizosphere of cowpea relative to bulk soil, while those of Ca and Mg were greater in the rhizosphere compared with bulk soil. With sorghum, only K, S, and Na were lower in the rhizosphere, in contrast to P, Ca, Mg, Cu, and Zn, which were higher in the rhizosphere. These differences in mineral concentration were due to alteration in rhizosphere pH, which was increased by cowpea but unchanged by sorghum. The data also showed that high plant density (166,666 plants.ha) and mixed culture significantly decreased rhizosphere soil pH, resulting in low availability of P, K, Ca, Mg, Na, S, Fe, Cu, Zn, Mn and B in the rhizosphere of cowpea and sorghum compared with low plant density (83,333 plants.ha) or monocropping. The results also showed significant differences in rhizosphere concentration of minerals between and among the five cowpea genotypes, with cv. Sanzie consistently indicating much lower levels of P and Ca as a result of higher root uptake, which was evidenced by the higher tissue content of P, K, Ca, Mg, Na, S, Fe, Zn, Mn and B in cv. Sanzie. Conclusion: N2-fixing cowpea significantly lowered the concentration and increased the uptake of mineral elements from the rhizosphere soil relative to sorghum.

Legume species in the fynbos vegetation of the Cape Floristic Region, that fix N2 in soils with low P, may have evolved for enhanced acquisition and efficient use of P. It was hypothesized that N2-fixing and combined-N supplied (N-supplied) A. linearis, P. calyptrata and C. genistoides are adapted to low P and would be relatively unresponsive to increased P of 100 μM. 18 legume species were evaluated for their nodulation response to low P availability. The N X P interaction was then examined in A. linearis, P. calyptrata and C. genistoides reliant on either N2-fixation or 300 μM N (NH4NO3), and receiving 0.1, 1.0, 10 and 100 μM P (NaH2PO4). In the species selection experiment, A. linearis, P. calyptrata and C. genistoides, with the greatest nodule fresh weight (FW) and nodule FW to root FW ratio, were the most prolific nodulating species. In the N X P experiment, with low P supply, the biomass of N2-fixing P. calyptrata and C. genistoides was consistently greater than that of N-supplied plants. In contrast, with high P supply of 100 μM P, all N-supplied plants accumulated more biomass than the corresponding N2-fixing plants. High P-use efficiency, poor down-regulation of P uptake and P storage was evident in A. linearis and P. calyptrata. The growth response to P and the significant N X P interactions indicate that N2-fixing and N-supplied plants were not adapted to low P, but rather colimited by both N and P.

The shoots of rooibos (Aspalathus linearis (Burm.f.) R.Dahlgren) plants, cultivated organically by small-scale farmers in Nieuwoudtville, are harvested for the production of tea. These practices could lead to decreasing soil fertility. It was hypothesised that soil from cultivated rooibos plots will have lower nutrient concentrations than soil from adjacent uncultivated plots. Soil and shoot samples were collected in December 2005, 2006 and 2009 from cultivated fields of increasing plot age and from adjacent uncultivated plots on three farms, and analysed for nutrient concentration. Compared with the uncultivated plots, no measured soil nutrients including concentrations of phosphorus (P), exchangeable potassium (K), magnesium (Mg) and calcium (Ca), and soil carbon (C) decreased in cultivated plots over the five-year period of assessment. Soil C correlated positively with concentrations of soil exchangeable K, Mg and Ca, and sodium (P < 0.001), indicating that soil C is an important indicator of soil fertility. Foliar P increased, and consequently the nitrogen:P ratio decreased in cultivated relative to uncultivated plants, implying higher P-uptake by cultivated plants. Overall, organic rooibos cultivation in Nieuwoudtville appears to be sustainable in terms of maintaining soil nutrition because soil nutrient status did not decrease over the five-year period.Keywords: Aspalathus, fynbos, legume, rooibos, soil fertility

Rhizobia of the genus Burkholderia have large-scale distribution ranges and are usually associated with South African papilionoid and South American mimosoid legumes, yet little is known about their genetic structuring at either local or global geographic scales. To understand variation at different spatial scales, from individual legumes in the fynbos (South Africa) to a global context, we analyzed chromosomal (16S rRNA, recA ) and symbiosis ( nifH , nodA , nodC ) gene sequences. We showed that the global diversity of nodulation genes is generally grouped according to the South African papilionoid or South American mimosoid subfamilies, whereas chromosomal sequence data were unrelated to biogeography. While nodulation genes are structured on a continental scale, a geographic or host-specific distribution pattern was not detected in the fynbos region. In host range experiments, symbiotic promiscuity of Burkholderia tuberum STM678 T and B . phymatum STM815 T was discovered in selected fynbos species. Finally, a greenhouse experiment was undertaken to assess the ability of mimosoid ( Mimosa pudica ) and papilionoid ( Dipogon lignosus , Indigofera filifolia , Macroptilium atropurpureum , and Podalyria calyptrata ) species to nodulate in South African (fynbos) and Malawian (savanna) soils. While the Burkholderia -philous fynbos legumes ( D . lignosus , I . filifolia , and P . calyptrata ) nodulated only in their native soils, the invasive neotropical species M . pudica did not develop nodules in the African soils. The fynbos soil, notably rich in Burkholderia , seems to retain nodulation genes compatible with the local papilionoid legume flora but is incapable of nodulating mimosoid legumes that have their center of diversity in South America. IMPORTANCE This study is the most comprehensive phylogenetic assessment of root-nodulating Burkholderia and investigated biogeographic and host-related patterns of the legume-rhizobial symbiosis in the South African fynbos biome, as well as at global scales, including native species from the South American Caatinga and Cerrado biomes. While a global investigation of the rhizobial diversity revealed distinct nodulation and nitrogen fixation genes among South African and South American legumes, regionally distributed species in the Cape region were unrelated to geographic and host factors.

The effects of elevated UV-B radiation and two nitrogen (N) sources on mineral nutrition of Cyclopia maculata, a UV-B-sensitive species, was assessed together with UV-B-tolerant symbiotic legumes Vigna unguiculata, Glycine max, Lupinus luteus, Vicia atropurpurea, Podalyria calyptrata and Virgilia oroboides. Plants were grown outdoors on tables under moderately or highly elevated UV-B exposures which simulated 15% and 25% ozone depletion above Cape Town in South Africa. Exposing purely symbiotic plants of V. unguiculata to elevated UV-B132 radiation decreased the tissue concentration of calcium (Ca) in leaves, phosphorus (P) in stems and roots, potassium (K) in roots, and boron (B) in roots and nodules relative to UV-B162 or ambient control. In contrast, seedlings of C. maculata, V. oroboides, L. luteus, and V. atropurpurea plants exposed to elevated UV-B radiation increased the concentration of several nutrients in leaves, stems and roots whereas P. calyptrata showed no changes in the mineral nutrition. ...

In fire-prone ecosystems, plants for the most part persist via either soil-stored seed banks (seeders) or below-ground storage structures (resprouters). Given their greater allocation of resources above ground to growth and reproduction, seeders are likely to have a higher nutrient requirement than resprouters. This may result in discernable differences in habitat nutrition and leaf morphology. These differences are probably accentuated in Cape legumes given their poor adaptation to low-P soils. It was hypothesized that legume seeders occupy habitats with greater fertility and possess larger, less sclerophyllous leaves than resprouters. Site nutrition and leaf morphologies were compared between seeders and resprouters in the genera Otholobium and Psoralea. There were no differences in leaf morphology between seeders and resprouters. Seeders sites had a higher total [N], exchangeable [Ca] and [Mg], and CEC, but lower [Fe] than resprouters. Only within Otholobium, did seeder sites have a higher Bray II [P]. This genus-specific variation in available P is probably a consequence of greater variation in soil type and precipitation between seeders and resprouters. Conversely, niche construction may contribute to the differences in soil fertility between seeders and resprouters in Psoralea. Thus, our data showed a general tendency for seeders to inhabit more fertile sites than resprouters. Caution is required, however, in generalizing these results, as our data indicate a difference in factors affecting soil nutrient availability between legume genera. Changes in soil fertility post-fire may limit legume persistence beyond the early stages of succession.

Insect pests are a major constraint to cowpea production in Africa. Therefore the aim of this study was to identify cowpea material that exhibit greater pest resistance and grain yield for evaluation by farmers. About 45 cowpea genotypes were assayed for flavonoids and anthocyanins with the objective of quantifying the levels of these phenolics in seed extracts as markers for effective plant defence. The results revealed significant differences in the concentration of flavonoids and anthocyanins in seed extract. Farmer varieties such as Sanzie, Bensogla and Omondaw exhibited much higher levels of phenolics compared with improved genotypes like ITH98-46, TVu1509 and IT93K-452-1. When planted in the field in Ghana and Tanzania, the genotypes that had high concentrations of flavonoids and anthocyanins in seed extracts (e.g. Bensogla, Omondaw and IT86D-2075) showed relatively lower infestation by thrips, pod-sucking bugs, aphids and alcidodes. Providing minimum protection with insecticide spray further showed that, genotypes with low infestation by thrips and pod-sucking bugs produced more grain yield without spraying, an indication of their natural resistance to these insect pests. Furthermore, farmer-selected varieties such as Sanzie, Bensogla, and Omondaw produced more grain yield without protection than their improved counterparts. These results showed that the higher the concentration of flavonoids and anthocyanins in cowpea seed extracts, the lower the insect pest incidence on seedlings raised from those seeds. Correlation analysis further confirmed a direct relationship between high flavonoids/anthocyanins in seed extracts and enhanced insect pest.

Abundance of Fabaceae declines in representation through post-fire-succession in fynbos vegetation of the Cape Floristic Region (CFR). This reduction in legume occurrence coincides with a known decline in post-fire soil P availability. It was hypothesized that the disappearance of legume species during post-fire succession is due to an inability to acquire P effectively from sparingly soluble sources. P-acquisition strategies and response to P supply were compared between legume (Aspalathus, Cyclopia, Indigofera, Podalyria) and non-legume (Elegia, Leucadendron, Protea) genera when supplied with 1 or 10 mg P kg−1 dry sand. Each genus consisted of a seeder (non-persistent) and resprouter (persistent) species. Non-legumes showed a greater investment in below-ground biomass, more root clusters, with higher concentrations of carboxylates exuded by cluster roots and carboxylates that were better suited to the mobilization of sparingly soluble P compared to legumes. The growth response to increased P supply was 53% higher in legumes than in non-legumes. The lack of a growth response to an elevated P supply in the non-legumes was attributed to N-limitation. Legume resprouters had a higher investment in cluster-root biomass and a lower capacity to down-regulate P-uptake than the seeders. Therefore the inability to acquire sufficient P from low concentration and sparingly soluble soil P-sources may contribute to the lack of indigenous legume persistence in fynbos vegetation of the CFR.

A field experiment involving two planting densities (83,333 and 166,666 plants per ha), two cropping systems (monoculture and mixed culture) and five cowpea [Vigna unguiculata L. (Walp.)] genotypes was conducted at Nietvoorbij (33°54S, 18°14E), Stellenbosch, South Africa, to select cowpea material with superior growth and water-use efficiency (WUE). The results showed significantly higher photosynthetic rates, stomatal conductance and transpiration in leaves of plants at low density and in monoculture due to greater chlorophyll (Chl) levels relative to those at high density and in mixed culture. As a result, C concentration in leaves and the amount of C, P, K, Ca, Mg, Fe, Cu, Zn, Mn, and B accumulated in shoots at low density and under monoculture were also much higher. Even though no marked differences in photosynthetic rates were found between and among the five cowpea genotypes, leaf C concentration and shoot C, P, K, Ca, Mg, Fe, Cu, Zn, Mn, and B contents differed considerably, with Sanzie exhibiting the highest C concentration and C, P, K, Ca, Mg, Fe, Cu, Zn, Mn, and B contents in shoots, followed by Bensogla and Omondaw, while ITH98-46 and TVu1509 had the lowest shoot concentration and contents of C, P, K, Ca, Mg, Fe, Cu, Zn, Mn, and B. WUE (calculated as photosynthate produced per unit water molecule transpired) was significantly greater in plants at low density and monoculture relative to those at high density and in mixed culture. Isotopic analysis revealed significant differences in δ13C values of sorghum [Sorghum bicolor L. (Moench.)] and cowpea, with higher δ13C values being obtained for plants at low density and in monoculture relative to those at high density or in mixed culture. The five cowpea genotypes also showed significant differences in δ13C values, with Sanzie exhibiting the most negative value (i.e. low WUE) and ITH98-46, the least negative δ13C value (i.e. high WUE). Whether measured isotopically or from gas-exchange studies, sorghum (a C4 species) exhibited much higher WUE relative to cowpea (a C3 species). Both correlation and regression analyses revealed a positive relationship between WUE from gas-exchange studies and δ13C values from isotopic analysis of cowpea and sorghum shoots.

In the low-P soil of the fynbos biome, plants have evolved several morphological and physiological P acquisition and use mechanisms, leading to variable uptake and use efficiencies. We expected that plants grown in low-P soils would exhibit greater P acquisition traits and hypothesised that Aspalathus linearis (Burm. f.) R. Dahlgren, a cluster-root-forming species adapted to drier and infertile soils, would be the most efficient at P acquisition compared with other species. Three fynbos Fabales species were studied: A. linearis and Podalyria calyptrata (Retz.) Willd, both legumes, and Polygala myrtifolia L., a nonlegume. A potted experiment was conducted where the species were grown in two soil types with high P (41.18 mg kg–1) and low P (9.79 mg kg–1). At harvest, biomass accumulation, foliar nutrients and P acquisition mechanisms were assessed. Polygala myrtifolia developed a root system with greater specific root length, root hair width and an average root diameter that exuded a greater amount of citrate and, contrary to the hypothesis, exhibited greater whole-plant P uptake efficiency. However, P. calyptrata had higher P use efficiency, influenced by N availability through N2 fixation. Specific root length, root length and root : shoot ratio were promising morphological traits for efficient foraging of P, whereas acid phosphatase exudation was the best physiological trait for solubilisation of P.

Over 760 legume species occur in the ecologically-heterogeneous Core Cape Subregion (CCR) of South Africa. This study tested whether the main symbionts of CCR legumes (Burkholderia and Mesorhizobium) are phylogenetically structured by altitude, pH and soil types. Rhizobial strains were isolated from field nodules of diverse CCR legumes and sequenced for 16S ribosomic RNA (rRNA), recombinase A (recA) and N-acyltransferase (nodA). Phylogenetic analyses were performed using Bayesian and maximum likelihood techniques. Phylogenetic signals were determined using the D statistic for soil types and Pagel’s λ for altitude and pH. Phylogenetic relationships between symbionts of the narrowly-distributed Indigofera superba and those of some widespread CCR legumes were also determined. Results showed that Burkholderia is restricted to acidic soils, while Mesorhizobium occurs in both acidic and alkaline soils. Both genera showed significant phylogenetic clustering for pH and most soil types, but not for altitude. Therefore, pH and soil types influence the distribution of Burkholderia and Mesorhizobium in the CCR. All strains of Indigofera superba were identified as Burkholderia, and they were nested within various clades containing strains from outside its distribution range. It is, therefore, hypothesized that I. superba does not exhibit rhizobial specificity at the intragenic level. Implications for CCR legume distributions are discussed.

A field experiment involving two plant densities (83,333 and 166,666 plants per hectare), two cropping systems (monoculture and mixed culture) and five cowpea (Vigna unguiculata L. Walp.) genotypes (3 farmer-selected varieties: Bensogla, Sanzie and Omondaw, and 2 breeder-improved cultivars: ITH98-46 and TVuI509) was conducted for two years in 2005 and 2006 at Nietvoorbij (33°54S, 18°14E), Stellenbosch, South Africa, to evaluate the effect of these treatments on the growth and symbiotic performance of cowpea. The results showed that, of the five cowpea genotypes, plant growth and N2 fixation were significantly greater in the three farmer-selected varieties (Sanzie, Bensogla and Omondaw) relative to the two improved cultivars (ITH98-46 and TVuI509). Furthermore, plant growth and symbiotic performance (measured as tissue N concentration, plant N content,15N natural abundance and N-fixed) were significantly (P

1. Indigenous species of Acacia are common in African savannas that have N-rich soils. This raises doubt regarding the extent of plant dependence on N 2 -fixation. Why would Acacia spp. enjoy an advantage over other tree species on N-replete soils? 2. We tested the hypothesis that competition by grass for nutrients would induce increased nodulation of Acacia karroo, A. nilotica, A. tortilis and A. nigrescens seedlings that would enable them to survive better than a non-nodulating congeneric species (A. ataxacantha). A glasshouse pot experiment was conducted to determine the capacity of the Acacia spp. to nodulate. The Acacia spp. were also grown in a randomized field plot experiment in Hluhluwe-iMfolozi Park with and without grass coexistence, and biomass accumulation and δ 15 N values were determined. We also sampled a range of legume and non-legume saplings from the Hluhluwe-iMfolozi Park for δ 15 N values. 3. In the pot experiment all species, except A. ataxacantha, which is a forest margin species, nodulated and consequently had lower δ 15 N isotope values than A. ataxacantha. In the field experiment the δ 15 N values of the plants grown with grass were significantly lower (δ 15 N = 0.77± 0.08‰) than those grown without grass (δ 15 N = 5.0 ± 0.16%o) for all species, except A. ataxacantha. The δ 15 N isotope abundances of field-collected leaves of legume saplings were found to be significantly lower than those of non-legume species (legume δ 15 N = 0.98 ± 0.32%o, non-legume δ 15 N = 2.15 ± 0.32%o). 4. These data confirm that A. karroo, A. nilotica, A. tortilis and A. nigrescens seedlings are capable of nodulating, and do so in their native habitat. The decreased δ 15 N in plants grown with grass indicates that N 2 fixation was strongly enhanced by competition with grass for N. 5. N 2 fixation may thus be an important attribute allowing legume tree seedlings to survive competition with grass through a critical period when tree roots and grass roots must compete for nutrients.

The Mediterranean Fynbos vegetation of South Africa is well known for its high levels of diversity, endemism, and the existence of very distinct plant communities on different soil types. Studies have documented the broad taxonomic classification and diversity patterns of soil microbial diversity, but none has focused on the community assembly processes. We hypothesised that bacterial phylogenetic community structure in the Fynbos is highly governed by deterministic processes. We sampled soils in four Fynbos vegetation types and examined bacterial communities using Illumina HiSeq platform with the 16S rRNA gene marker. UniFrac analysis showed that the community clustered strongly by vegetation type, suggesting a history of evolutionary specialisation in relation to habitats or plant communities. The standardised beta mean nearest taxon distance (ses. β NTD) index showed no association with vegetation type. However, the overall phylogenetic signal indicates that distantly related OTUs do tend to co-occur. Both NTI (nearest taxon index) and ses. β NTD deviated significantly from null models, indicating that deterministic processes were important in the assembly of bacterial communities. Furthermore, ses. β NTD was significantly higher than that of null expectations, indicating that co-occurrence of related bacterial lineages (over-dispersion in phylogenetic beta diversity) is determined by the differences in environmental conditions among the sites, even though the co-occurrence pattern did not correlate with any measured environmental parameter, except for a weak correlation with soil texture. We suggest that in the Fynbos, there are frequent shifts of niches by bacterial lineages, which then become constrained and evolutionary conserved in their new environments. Overall, this study sheds light on the relative roles of both deterministic and neutral processes in governing bacterial communities in the Fynbos. It seems that deterministic processes play a major role in assembling the bacterial community, with neutral processes playing a more minor role.

Rhizobial diversity and host preferences were assessed in 65 native Fynbos legumes of the papilionoid legume tribes Astragaleae, Crotalarieae, Genisteae, Indigofereae, Millettieae, Phaseoleae, Podalyrieae, Psoraleeae and Sesbanieae. Sequence analyses of chromosomal 16S rRNA, recA, atpD and symbiosis-related nodA, nifH genes in parallel with immunogold labelling assays identified the symbionts as alpha- (Azorhizobium, Bradyrhizobium, Ensifer, Mesorhizobium and Rhizobium) and beta-rhizobial (Burkholderia) lineages with the majority placed in the genera Mesorhizobium and Burkholderia showing a wide range of host interactions. Despite a degree of symbiotic promiscuity in the tribes Crotalarieae and Indigofereae nodulating with both alpha- and beta-rhizobia, Mesorhizobium symbionts appeared to exhibit a general host preference for the tribe Psoraleeae, whereas Burkholderia prevailed in the Podalyrieae. Although host genotype was the main factor determining rhizobial diversity, ecological factors such as soil acidity and site elevation were positively correlated with genetic variation within Mesorhizobium and Burkholderia, respectively, indicating an interplay of host and environmental factors on the distribution of Fynbos rhizobia. ispartof: FEMS Microbiology Ecology vol:91 issue:2 pages:2-17 ispartof: location:England status: published

Nitrate deposition from anthropogenic activities into nutrient impoverished soils of Mediterranean ecosystems represents a significant income to their N economy, which may potentially increase the sensitivity of those typically UV-B (280–315 nm) resilient plants from these ecosystems with superior photosynthetic rates especially to increases in solar UV-B flux due to ozone depletion. This proposal was examined by exposing nodulated Podalyria calyptrata seedlings for 6-months in nitrate deficient and nitrate replete sand culture to biologically effective UV-B (UV-BBE) supplements approximating 40 and 77% above clear-sky background (control) at an outdoor site. Leaf photosynthesis and chemical composition of purely symbiotic plants were unaffected by increased UV-BBE. Conversely, nodulated plants that received nitrate supplements displayed a linear reduction in stomatal conductance (gS) but non-linear asymptotic reductions in light-saturated net CO2 assimilation rate (Asat), apparent carboxylation efficiency (ACE) and nitrogen use efficiency (NUE) with increased UV-BBE. RuBP regeneration limitations on CO2 assimilation were not apparent, since Asat at saturating internal leaf CO2 concentrations displayed insignificant depressions with increased UV-BBE. Nor was there any suggestion of diminished light absorption capacity of antenna complexes, or of photosynthetic inhibition due to starch accumulation, since leaf chlorophyll and carotenoid contents and non-structural carbohydrate concentrations were insignificantly altered by increased UV-BBE. Also, there seemed unlikely photosynthetic inhibition due to reduced allocation of N to Rubisco with increased UV-BBE in the nitrate-fed plants, since both ACE and Asat were negatively correlated with leaf N content, much of which probably constituted assimilated nitrate according to the less negative δ15N values. We suggest that the molecular processes that rendered P. calyptrata plants receiving nitrate supplements more sensitive to photosynthetic inhibition by increased UV-BBE may be related indirectly to their more active metabolic state, this apparent from their elevated respiratory and photosynthetic rates, rather than to any direct UV-B effects on CO2 uptake and fixation.

Seventeen herb, shrub and tree species of commercial and ecological importance in southern Africa were exposed at one location to ultraviolet‐B (UV‐B, 280–315 nm) radiation approx. 35 % above clear‐sky background (control). The aims were to assess how UV‐B affects canopy area, dry mass, and some biochemical and morphological properties of leaves, and to investigate whether differences between species are related to growth form of the plants. There was no pattern of response to UV‐B related to growth form. Leaves of trees had altered chlorophyll a and b, carotenoid and flavonoid concentrations, but those of shrubs or herbs did not. Non‐structural carbohydrates were unaffected. Smaller canopy areas and dry masses were observed under enhanced UV‐B, but these were not statistically different among growth forms. There was a general insensitivity of species to elevated UV‐B. Only five species had significantly altered leaf biochemical and morphological properties, canopy area and dry mass, the changes differing in magnitude. There was no consistent pattern of change in leaf thickness or biochemical composition with increased UV‐B. Correlation analyses did not support the view that growth is less negatively affected in species with thick leaves or in those where leaf thickness increases, or in species with naturally high leaf flavonoid contents or that are able to synthesize additional flavonoids in response to UV‐B enhancement. The analyses did not support the hypothesis that growth was inhibited by starch accumulation in leaves under elevated UV‐B. However, changes in leaf shape did correlate with canopy area and dry mass, showing the importance of photomorphogenetic changes caused by UV‐B which affect species’ performance. We conclude that generalizations on plant sensitivity to UV‐B based on growth form and functional type could be misleading, and that the great majority of economically important species of the region are likely to be insensitive to future UV‐B increases. Notable exceptions include the Colophospermum mopane tree ecotypes chota and leslie and the arable annual Vigna unguiculata, both of which are traditional sources of livelihood to rural African populations and of importance to African industry and agriculture.