Mechanisms for minimizing height-related stomatal conductance declines in tall vines.

The ability to transport water through tall stems hydraulically limits stomatal conductance (gs ), thereby constraining photosynthesis and growth. However, some plants are able to minimize this height-related decrease in gs , regardless of path length. We hypothesized that kudzu (Pueraria lobata) prevents strong declines in gs with height through appreciable structural and hydraulic compensative alterations. We observed only a 12% decline in maximum gs along 15-m-long stems and were able to model this empirical trend. Increasing resistance with transport distance was not compensated by increasing sapwood-to-leaf-area ratio. Compensating for increasing leaf area by adjusting the driving force would require water potential reaching -1.9 MPa, far below the wilting point (-1.2 MPa). The negative effect of stem length was compensated for by decreasing petiole hydraulic resistance and by increasing stem sapwood area and water storage, with capacitive discharge representing 8-12% of the water flux. In addition, large lateral (petiole, leaves) relative to axial hydraulic resistance helped improve water flow distribution to top leaves. These results indicate that gs of distal leaves can be similar to that of basal leaves, provided that resistance is highest in petioles, and sufficient amounts of water storage can be used to subsidize the transpiration stream.

The effects of Pueraria mirifica extract, diadzein and genistein in testosterone-induced prostate hyperplasia in male Sprague Dawley rats.

Pueraria mirifica (PM) is a medicinal plant native to Thailand contained high amount of phytoestrogen and possesses anticancer activity. This study reports the effect of P. mirifica extract, phytoestrogen of diadzein and genistein for its benign prostate hyperplasia properties in testosterone-induced prostate hyperplasia in male Sprague Dawley rats. The P. mirifica extract was evaluated for its total phenols, flavonoid and antioxidant activity using DPPH, FRAP and metal chelating assay. The assessment of P. mirifica, diadzein and genistein against benign prostate hyperplasia was determined in testosterone-induced prostate hyperplasia in male Sprague Dawley rats. The total phenol was higher than flavonoid but showed low antioxidant activity of DPPH, FRAP and metal chelating. The aqueous PM extract at 1000 mg/kg significantly increased testosterone levels in testosterone-induced rats by 13% while diadzein and genistein increased it by 11% and 17% respectively. However, levels of FSH, LH, triglyceride and HDL are not affected by the oral administration of PM, diadzein and genistein to the rats. Similarly, total protein, albumin, globulin, total bilirubin, conjugated bilirubin, alkaline phosphatase, alanine aminotransferase, AST, and G-glutamyltransferase showed no significant difference as compared with negative control rats. The body weight of the rats, testis, kidney and liver showed no toxic effect. The zinc content increased significantly and the zinc transporter gen of ZnT4 and ZIP4 highly expressed suggesting that the PM, diadzein and genistein plays essential role in modulating prostate zinc homeostasis. Similarly, the expression of IL-6, AR and ER was significantly reduced indicating functioning in regulation of prostate growth and acts as anti-inflammatory role in preventing BPH. In conclusion, the results indicated that PM reduced BPH and contributed to the regulation in the zinc transport expression of the prostate cells in the benign prostate hyperplasia (BPH).

How well do growing season dynamics of photosynthetic capacity correlate with leaf biochemistry and climate fluctuations?

Accurate values of photosynthetic capacity are needed in Earth System Models to predict gross primary productivity. Seasonal changes in photosynthetic capacity in these models are primarily driven by temperature, but recent work has suggested that photoperiod may be a better predictor of seasonal photosynthetic capacity. Using field-grown kudzu (Pueraria lobata (Willd.) Ohwi), a nitrogen-fixing vine species, we took weekly measurements of photosynthetic capacity, leaf nitrogen, and pigment and photosynthetic protein concentrations and correlated these with temperature, irradiance and photoperiod over the growing season. Photosynthetic capacity was more strongly correlated with photoperiod than with temperature or daily irradiance, while the growing season pattern in photosynthetic capacity was uncoupled from changes in leaf nitrogen, chlorophyll and Rubisco. Daily estimates of the maximum carboxylation rate of Rubisco (Vcmax) based on either photoperiod or temperature were correlated in a non-linear manner, but Vcmax estimates from both approaches that also accounted for diurnal temperature fluctuations were similar, indicating that differences between these models depend on the relevant time step. We advocate for considering photoperiod, and not just temperature, when estimating photosynthetic capacity across the year, particularly as climate change alters temperatures but not photoperiod. We also caution that the use of leaf biochemical traits as proxies for estimating photosynthetic capacity may be unreliable when the underlying relationships between proxy leaf traits and photosynthetic capacity are established outside of a seasonal framework.

A new strategy for controlling invasive weeds: selecting valuable native plants to defeat them.

To explore replacement control of the invasive weed Ipomoea cairica, we studied the competitive effects of two valuable natives, Pueraria lobata and Paederia scandens, on growth and photosynthetic characteristics of I. cairica, in pot and field experiments. When I. cairica was planted in pots with P. lobata or P. scandens, its total biomass decreased by 68.7% and 45.8%, and its stem length by 33.3% and 34.1%, respectively. The two natives depressed growth of the weed by their strong effects on its photosynthetic characteristics, including suppression of leaf biomass and the abundance of the CO2-fixing enzyme RUBISCO. The field experiment demonstrated that sowing seeds of P. lobata or P. scandens in plots where the weed had been largely cleared produced 11.8-fold or 2.5-fold as much leaf biomass of the two natives, respectively, as the weed. Replacement control by valuable native species is potentially a feasible and sustainable means of suppressing I. cairica.

Phenotypic plasticity of Neonotonia wightii and Pueraria phaseoloides grown under different light intensities.

Plants have the ability to undergo morphophysiological changes based on availability of light. The present study evaluated biomass accumulation, leaf morphoanatomy and physiology of Neonotonia wightii and Pueraria phaseoloides grown in full sunlight, as well as in 30% and 50% shade. Two assays were performed, one for each species, using a randomized block design with 10 replicates. A higher accumulation of fresh mass in the shoot of the plants was observed for both species under cultivation in 50% shade, while no differences were detected between the full sunlight and 30% shade. N. wightii and P. phaseoloides showed increase in area and reduction in thickness leaf when cultivated in 50% shade. There were no changes in photosynthetic rate, stomatal conductance, water use efficiency and evapotranspiration of P. phaseoloides plants because growth environment. However, the shade treatments caused alterations in physiological parameters of N. wightii. In both species, structural changes in the mesophyll occurred depending on the availability of light; however, the amount of leaf blade tissue remained unaltered. Despite the influence of light intensity variation on the morphophysiological plasticity of N. wightii and P. phaseoloides, no effects on biomass accumulation were observed in response to light.

Diffusion-based process for carbon dioxide uptake and isoprene emission in gaseous/aqueous two-phase photobioreactors by photosynthetic microorganisms.

Photosynthesis for the generation of fuels and chemicals from cyanobacteria and microalgae offers the promise of a single host organism acting both as photocatalyst and processor, performing sunlight absorption and utilization, as well as CO(2) assimilation and conversion into product. However, there is a need to develop methods for generating, sequestering, and trapping such bio-products in an efficient and cost-effective manner that is suitable for industrial scale-up and exploitation. A sealed gaseous/aqueous two-phase photobioreactor was designed and applied for the photosynthetic generation of volatile isoprene (C(5)H(8)) hydrocarbons, which operates on the principle of spontaneous diffusion of CO(2) from the gaseous headspace into the microalgal or cyanobacterial-containing aqueous phase, followed by photosynthetic CO(2) assimilation and isoprene production by the transgenic microorganisms. Volatile isoprene hydrocarbons were emitted from the aqueous phase and were sequestered into the gaseous headspace. Periodic replacement (flushing) of the isoprene (C(5)H(8)) and oxygen (O(2)) content of the gaseous headspace with CO(2) allowed for the simultaneous harvesting of the photoproducts and replenishment of the CO(2) supply in the gaseous headspace. Reduction in practice of the gaseous/aqueous two-phase photobioreactor is offered in this work with a fed-batch and a semi-continuous culturing system using Synechocystis sp. PCC 6803 heterologously expressing the Pueraria montana (kudzu) isoprene synthase (IspS) gene. Constitutive isoprene production was observed over 192 h of experimentation, coupled with cyanobacterial biomass accumulation. The diffusion-based process in gaseous/aqueous two-phase photobioreactors has the potential to be applied to other high-value photosynthetically derived volatile molecules, emanating from a variety of photosynthetic microorganisms.

Leaf-lamina conductance contributes to an equal distribution of water delivery in current-year shoots of kudzu-vine shoot, Pueraria lobata.

Leaf-lamina resistance, R(L), accounts for a large fraction of branch resistance across a wide range of plant species. This work hypothesized that large R(L) is essential for distributing water equally to leaves on the shoot, and tested this hypothesis through theoretical analyses and measurements using over 10-m-long current-year shoots of kudzu vine, Pueraria lobata [Willd.] Ohwi. First, the hydraulic architecture and the distribution of the motive force achieving equal distribution of water delivery were theoretically obtained by simulating water flow through a hypothetical shoot comprising an axial pathway and several lateral pathways as a stem and leaves, respectively, in a kudzu-vine shoot. The model predicts that large resistance of the lateral pathway relative to that of the axial pathway is associated strongly with small variation in the hydraulic conductance of a pathway from the base of the axial pathways to the lateral pathway among the nodes, rendering water delivery to each lateral pathway equal under small variation in motive force for water flow. For the kudzu-vine shoot, the measured ratio of the lateral (a petiole) to the axial (a stem) resistance was 115. When R(L) was added to the lateral pathway, the ratio increased to 1136. According to the model prediction, these values imply that the hydraulic conductance of a pathway comprising a stem and a petiole, K(BP), is favored strongly at the basal nodes, while the hydraulic conductance of a pathway including a stem, a petiole and a lamina, K(SL), is slightly different across the nodes. For the shoots with leaf lamina, the diurnal change in transpiration rate was not different between the leaves on the three nodes dividing the shoot into four parts. K(SL) was not related significantly to node number. Conversely, K(BP) at the distal node was ~0.06-fold that at the basal node. Furthermore, the motive force for water flow should vary by 6.64-fold among nodes to compensate for the favored distribution of K(BP), which is an unrealistic value. These results indicate that R(L) contributes largely to an equal distribution of water delivery in a shoot, supporting our hypothesis.

Suitability of Pueraria phaseoloides, Chromolaena odorata and Tithonia diversifolia as in-situ mulch for nematode management in musa cropping systems.

Mulching with plant organic matter has been shown to reduce nematode population densities in various cropping systems. The level of nematode control is increased when such mulches are incorporated into the soil as organic amendments. Chromolaena odorata, Tithonia diversifolia and Pueraria phaseoloides are common cover crops in West and Central Africa that produce large quantities of nutrient rich biomass. The aim of this study was to determine, if in-situ mulching of C. odorata, T. diversifolia and P. phaseoloides is suitable for nematode control in Musa production. In a pot trial, the susceptibility of these plants to spiral nematodes was investigated. The effects of different quantities of surface mulch on nematode population densities in the soil and in banana roots also were determined. All mulch types and all quantities led to a reduction in nematode population densities in the soil. The strongest nematode reductions were observed in the Pueraria treatments. In treatments containing banana plants mulching improved plant growth compared to the clean-fallowed soil and induced lower root infestation rates. However, nematode soil populations were higher in mulched than in non-mulched banana treatments. Plant parasitic nematodes also were isolated from roots of all three cover crop species and all three plants caused an increase in nematode numbers in the soil. Therefore, the tested cover crops proved unsuitable for nematode control in a system with the highly susceptible bananas. Further examinations are needed to determine whether or not the positive effects of surface mulching on plantain plant growth and root infestation rates also have positive effects on yield in an in-situ mulching system in the presence of nematodes.

Comparison of phytotoxicity and mammalian cytotoxicity of nontrichothecene mycotoxins.

The phytotoxicity and mammalian cytotoxicity of four nontrichothecene mycotoxins (apicidin, sambutoxin, wortmannin, HC-toxin) were compared. Phytotoxicity was evaluated in terms of electrolyte leakage, growth inhibition, and reduction in chlorophyll content. Based on the parameters evaluated, the relative order of phytotoxicity to duckweed (Lemna pausicostata L.) was wortmannin > HC-toxin > apicidin >> sambutoxin. A 48-hr exposure to 10 microM wortmannin, HC-toxin or apicidin caused electrolyte leakage from duckweed. The IC50 values for growth inhibition and chlorophyll reduction for wortmannin, HC-toxin, and apicidin were 0.2 and 2.6 microM, 15.4 and 12.6 microM, and 27.7 and 45.3 microM, respectively. Based on the parameters measured, a 72-hr exposure to 100 microM sambutoxin was not toxic to duckweed. Kudzu (Pueraria lobata L.) leaf disc assays revealed a similar trend in relative toxicities, but higher mycotoxin concentrations were required to elicit phytotoxic effects compared to duckweed. All four mycotoxins were cytotoxic to four mammalian cell cultures. However, in contrast to plants, wortmannin was the least toxic (IC50 = 10 to 20 microM) and sambutoxin exhibited a high level of toxicity (IC50 = 0.5 to 1 microM).