A taxonomic revision of <Emphasis Type="Italic">Bursera</Emphasis> subgen. <Emphasis Type="Italic">Bursera</Emphasis> in the Greater Antilles and the Bahamas,including a new species from Cuba

A revision of Bursera in the Greater Antilles and the Bahamas has confirmed that Commiphora does not occur in the region and that all but one species in the region belong to Bursera subgen. Bursera. Here we describe a new species, Bursera yaterensis; B. nashii is synonymized with B. glauca and B. ovata is synonymized with B. trinitensis; and we return five species from Commiphora to Bursera. A dichotomous key is provided using mostly vegetative characters due to the frequent lack of adequate reproductive material and the relative uniformity of most floral and fruit characters.     

Massive excretion of calcium oxalate from late prepupal salivary glands of Drosophila melanogaster demonstrates active nephridial‐like anion transport

The Drosophila salivary glands (SGs) were well known for the puffing patterns of their polytene chromosomes and so became a tissue of choice to study sequential gene activation by the steroid hormone ecdysone. One well‐documented function of these glands is to produce a secretory glue, which is released during pupariation to fix the freshly formed puparia to the substrate. Over the past two decades SGs have been used to address specific aspects of developmentally‐regulated programmed cell death (PCD) as it was thought that they are doomed for histolysis and after pupariation are just awaiting their fate. More recently, however, we have shown that for the first 3–4 h after pupariation SGs undergo tremendous endocytosis and vacuolation followed by vacuole neutralization and membrane consolidation. Furthermore, from 8 to 10 h after puparium formation (APF) SGs display massive apocrine secretion of a diverse set of cellular proteins. Here, we show that during the period from 11 to 12 h APF, the prepupal glands are very active in calcium oxalate (CaOx) extrusion that resembles renal or nephridial excretory activity. We provide genetic evidence that Prestin, a Drosophila homologue of the mammalian electrogenic anion exchange carrier SLC26A5, is responsible for the instantaneous production of CaOx by the late prepupal SGs. Its positive regulation by the protein kinases encoded by fray and wnk lead to increased production of CaOx. The formation of CaOx appears to be dependent on the cooperation between Prestin and the vATPase complex as treatment with bafilomycin A₁ or concanamycin A abolishes the production of detectable CaOx. These data demonstrate that prepupal SGs remain fully viable, physiologically active and engaged in various cellular activities at least until early pupal period, that is, until moments prior to the execution of PCD.     

Genetic diversity and morphological variability in the Balkan endemic Campanula secundiflora s.l. (Campanulaceae)

We reconstructed the relationships among populations of Campanula secundiflora s.l. and closely related and geographically close populations of C. austroadriatica and C. versicolor. Based on analyses of microsatellite DNA data, the investigated populations have high overall genetic diversity and abundant allelic variation over seven investigated loci. Bayesian model‐based clustering identified four clearly differentiated genetic groups of populations. The genetic differentiation was reflected by morphological differentiation, allowing us to propose a new taxonomic treatment of the constituents of C. secundiflora s.l. The populations distributed in south‐western Serbia and north‐eastern Montenegro were included in C. secundiflora. A new species, C ampanula montenegrina sp. nov. , distributed in the continental part of Montenegro and the northern part of Albania is described. © 2015 The Linnean Society of London, Botanical Journal of the Linnean Society, 2016, 180 , 64–88.     

Scale-dependent bi-trophic interactions in a semi-arid savanna: how herbivores eliminate benefits of nutrient patchiness to plants

The scale of resource heterogeneity may influence how resources are locally partitioned between co-existing large and small organisms such as trees and grasses in savannas. Scale-related plant responses may, in turn, influence herbivore use of the vegetation. To examine these scale-dependent bi-trophic interactions, we varied fertilizer [(nitrogen (N)/phosphorus (P)/potassium (K)] applications to patches to create different scales of nutrient patchiness (patch size 2 × 2 m, 10 × 10 m, or whole-plot 50 × 50 m) in a large field experiment in intact African savanna. Within-patch fertilizer concentration and the total fertilizer load per plot were independently varied. We found that fertilization increased the leaf N and P concentrations of trees and grasses, resulting in elevated utilization by browsers and grazers. Herbivory off-take was particularly considerable at higher nutrient concentrations. Scale-dependent effects were weak. The net effect of fertilization and herbivory was that plants in fertilized areas tended to grow less and develop smaller rather than larger standing biomass compared to plants growing in areas that remained unfertilized. When all of these effects were considered together at the community (plot) level, herbivory completely eliminated the positive effects of fertilization on the plant community. While this was true for all scales of fertilization, grasses tended to profit more from coarse-grained fertilization and trees from fine-grained fertilization. We conclude that in herbivore-dominated communities, such as the African savanna, nutrient patchiness results in the herbivore community profiting rather more than the plant community, irrespective of the scale of patchiness. At the community level, the allometric scaling theory’s prediction of plant—and probably also animal—production does not hold or may even be reversed as a result of complex bi-trophic interactions.     

Short-term partitioning of Cd recently taken up between sunflowers organs (<Emphasis Type="Italic">Helianthus annuus</Emphasis>) at flowering and grain filling stages: effect of plant transpiration and allometry

Aims

This work concentrated on understanding the allocation of Cd recently taken up between the organs of sunflower at early and middle reproductive growth stages. The roles of transpiration and allometry were investigated.

Methods

Sunflowers were grown hydroponically in greenhouse, being exposed to low concentrations of Cd (pCd²⁺ = 11.03). At flower bud and grain filling stages, plants were exposed for three days to ¹¹¹Cd and at the same time, subjected or not to fans to increase the transpiration. The partitioning of ¹¹¹Cd between plant organs measured by high resolution ICP-MS was then modelled.

Results

Although the use of fans increased the plant water uptake and transpiration by about 20%, there were no significant effects on the partitioning of recent Cd. Most of the recent Cd was recovered in roots (60%) and only 2.8% were found in seeds (0.8% for the husk and 2.0% for the almonds). The sequestration of recent Cd in a plant organ was successfully explained by its biomass and except for leaves, by the biomass of other organs acting as competitive sinks.

Conclusions

This work proposes a modelling approach for the partitioning of the labelled Cd between plant organs in sunflower.

     

Linking root traits and competitive success in grassland species

Background and aims

Measures of phosphorus (P) in roots recovered from soil underestimate total P accumulation below-ground by crop species since they do not account for P in unrecovered (e.g., fine) root materials. ³³P-labelling of plant root systems may allow more accurate estimation of below-ground P input by plants.

Methods

Using a stem wick-feeding technique ³³P-labelled phosphoric acid was fed in situ to canola (Brassica napus) and lupin (Lupinus angustifolius) grown in sand or loam soils in sealed pots.

Results

Recovery of ³³P was 93 % in the plant-soil system and 7 % was sorbed to the wick. Significantly more ³³P was allocated below-ground than to shoots for both species with 59–90 % of ³³P measured in recovered roots plus bulk and rhizosphere soil. ³³P in recovered roots was higher in canola than lupin regardless of soil type. The proportion of ³³P detected in soil was greater for lupin than canola grown in sand and loam (37 and 73 % lupin, 20 and 23 % canola, respectively). Estimated total below-ground P accumulation by both species was at least twice that of recovered root P and was a greater proportion of total plant P for lupin than canola.

Conclusion

Labelling roots using ³³P via stem feeding can empower quantitative estimates of total below-ground plant P and root dry matter accumulation which can improve our understanding of P distribution in soil-plant systems.

     

No need to breed for enhanced colonization by arbuscular mycorrhizal fungi to improve low-P adaptation of West African sorghums

Background and aims

Herbaspirillum seropedicae (Hs) Z67 a diazotrophic endophyte was genetically engineered for secretion of 2-keto-D-gluconic acid by heterologous expression of genes for pqq synthesis and gluconate dehydrogenase to study its beneficial effect on plants.

Methods

Two plasmids, pJNK5, containing a 5.1 Kb pqq gene cluster of Acinetobacter calcoaceticus and pJNK6, carrying in addition the Pseudomonas putida KT2440 gluconate dehydrogenase (gad) operon were constructed in pUCPM18Gm^r under Plac promoter. H. seropedicae Z67 transformants were monitored for P and K solubilization, cadmium (Cd) tolerance and rice growth promotion.

Results

Hs (pJNK5) secreted 23.5 mM gluconic acid and Hs (pJNK6) secreted 3.79 mM gluconic acid and 15.8 mM 2-ketogluconic acid respectively. Under aerobic conditions, Hs (pJNK5) and Hs (pJNK6) solubilized 239.7 μM and 457.7 μM P on HEPES rock phosphate and, 76.7 μM and 222.7 μM K on HRPF (feldspar), respectively, in minimal medium containing 50 mM glucose. Under N free minimal medium, similar effects of P and K solubilization were obtained. Hs (pJNK5) and Hs (pJNK6) inoculation increased the biomass, N, P, K content of rice plants (Gujarat – 17). These plants also accumulated 0.73 ng/g PQQ, and had improved growth and tolerance to CdCl₂.

Conclusions

Incorporation of pqq and gad gene clusters in H. seropedicae Z67 imparted additional plant growth promoting traits of P and K solubilization and ability to alleviate Cd toxicity to the host plant.

     

The effects of root surface charge and nitrogen forms on the adsorption of aluminum ions by the roots of rice with different aluminum tolerances

Aim

Our objectives were to compare effects of root charge properties on Al adsorption by the roots of rice that differed in Al-tolerance, and to examine effects of different nitrogen forms on charge properties of rice roots and Al adsorption.

Methods

Streaming potential and chemical methods were used to measure root zeta potential and investigate Al chemical forms adsorbed on the roots of rice obtained from solution culture experiments.

Results

Rice roots of the Al-sensitive variety Yangdao-6 carried greater negative charge than the Al-tolerant variety Wuyunjing-7, which meant the roots of Yangdao-6 adsorbed more exchangeable and complexed Al. When both rice varieties were grown in NH₄ ⁺-containing nutrient solutions, there were less functional groups and lower negative surface charge on their roots, which reduced Al adsorption compared to the rice grown in NO₃ ^? containing nutrient solutions. The decline in nutrient solution pH due to NH₄ ⁺ uptake by rice roots was responsible for the reduced numbers of functional groups and the lower negative surface charge on the roots compared to the rice grown in NO₃ ^? containing solutions.

Conclusions

Integrated root surface charge, as expressed by zeta potential, played an important role in Al adsorption by the roots of rice with different Al-tolerance.