The influence of nitrate and ammonium forms of nitrogen fertilizer on the growth and osmoregulation of Digitaria eriantha and Chloris gayana grown under saline conditions.

Digitaria eriantha and Chloris gayana were grown under controlled conditions for three months and were treated with a nutrient solution containing 150 mMol NaCl and the following nitrogen sources: 25 or 200 mg/l NH4 +-N or NO3 +-N or no nitrogen. The application of nitrogen was found to stimulate growth, i.e. leaf area and dry mass in both grasses, with a greatest growth response to both NH4 +-N treatments in D. eriantha, and NH4 +-N and NO3 --N treatments in C. gayana. Proline accumulated in both grasses, but this accumulation followed different trends in the two grasses. Soluble sugars (non-structural) accumulated in the above ground component in D. eriantha, while in C. gayana soluble sugars accumulated predominantly in the roots, possibly as osmotica, or for storage and may thus have been available for regrowth.Keywords: ammonia; ammonium; ammonium nitrogen; chloris gayana; digitaria eriantha; dry mass; fertilizer; grass; growth; growth response; leaf; leaf area; nitrate nitrogen; nitrogen fertilizer; nitrogen source; osmoregulation; proline; regrowth; sodium chloride; soluble sugars; treatment

The influence of different forms and concentrations of nitrogen on total nonstructural carbohydrate allocation and growth in Digitaria eriantha.

Digitaria eriantha plants were grown under controlled conditions for a period of three months, during which time they were supplied with the following forms and concentrations of nitrogen: 50 mg/l NO3 - -N, 200 mg/l NO3 -N, 200mg/l NH4 +-N and a combined form containing both NO3 - -N and NH4 + -N with a nitrogen concentration of 200 mg/l. Control plants received no nitrogen. At monthly intervals both above and below ground components were assayed for soluble and insoluble carbohydrate contents. Dry mass and leaf areas were also measured. The nitrogen treatments were found to influence the allocation of photosynthates into either soluble or insoluble carbohydrates. In above ground tissue, the soluble carbohydrate component decreased with time, while the insoluble component increased with time. In root tissue the reverse trends were observed. Both dry mass and leaf area development were enhanced in plants supplied with nitrogen in any form. It was suggested that growth of D. eriantha was influenced by carbohydrate fluctuations.D. erianthaKeywords: botany; carbohydrates; digitaria eriantha; dry mass; growth; leaf area; leaves; nitrogen; physiology; plant physiology; south afric

A comparative histochemical study of plant polyphenols in southern African grasses.

Recent anatomical studies have shown that tannin-like substances (TLS) occur in the epidermal cells of a number of southern African tropical grasses, and the presence of condensed tannins in grasses has been confirmed by chemical analyses. A number of species from four of the five subfamilies of the Poaceae were compared for their responses to a range of histochemical tests which differ in their specificity for phenolic compounds. These included: ferrous sulphate, acidified vanillin, diazotized sulphanilic acid, Fast Blue-BB, dimethoxybenzaldehyde and nitrous acid, Safranin and Fast Green. In addition, the radial diffusion test for protein precipitation was used. Comparative histochemical tests indicated that most taxa known to contain TLS showed comparable responses to the tests used here, with variations in intensity and hue of the coloured products formed. These qualitative differences suggest the presence of a number of different compounds including oligomeric procyanidins, oligomeric prodelphinidins, monomeric and/or dimeric flavan-3-ols and flavan -3, 4-diols. The presence flavan-4-ols has been confirmed in the andropogonoid grasses by previous workers. Histochemical tests are adequate to identify the presence of condensed tannins and their precursors in plant tissue. However, they do not provide a means to identify those compounds which precipitate protein and function as digestibility-reducing compounds in plant-herbivore interactions.Language: EnglishKeywords: chemical analyses; Condensed tannins; Flavan-4-ols; grasses; Histochemical tests; interaction; phenolic compounds; poaceae; polyphenols; Proanthocyanidins; southern africa; Tannin-like substances; Tannins; TLS; tropical gras

Short Communication:The presence of condensed tannin in the leaves of Eulalia villosa.

The hypothesis that grasses contain tannin deposits in the leaf epidermal cells was tested using the leaf laminas of a Southern African sourveld grass, Eulalia villosa (Thunb.) Nees. The leaf material was assayed for total phenols, condensed tannin and biologically-active tannins. Catechin equivalents of 57.4 and 76.1 mg g exp -1 dry mass were obtained for total phenols and condensed tannin, respectivelyLanguage: EnglishKeywords: Biologically-active tannin; Eulalia villosa [Thunb.] Nees; Grass species; Leaf lamina tissue; Sourveld grass; Tannins; dry mass; leaves; total phenols; eulalia villosa; hypothesis; grasses; pheno

South Africa's bioprospecting, access and benefit-sharing legislation : current realities, future complications, and a proposed alternative

Globally, many nations are legislating access for bioprospecting purposes to their biological and genetic resources. South Africa, as a megadiverse country, has recently regulated bioprospecting, access and benefit-sharing activities in accordance with its obligations as a ratifying party to the Convention on Biological Diversity. The context and process of key legislation developments in South Africa are discussed, prior to our presenting a critique which emphasizes the practical impacts, especially on drug discovery, arising from the newly introduced systems. Probable effects on existing bioresource-based industries within South Africa, together with current as well as future bioprospecting activities, are assessed. Several practicalities of bioprospecting methods have been poorly accommodated, resulting in the development of impracticable and unnecessarily restrictive regulations. We conclude that though well-intentioned, these non-facilitative regulations have placed a dead hand on value-addition to South Africa's biodiversity. Bioprospectors will find it difficult to continue with broad-scale screening programmes given their user insecurity, legal uncertainty, and cost-inefficiency. Existing bioresource-based industries within South Africa face potential closure in view of onerous bioprospecting permit application requirements. An alternative, practical, CBD-compliant model on which to base urgently required legislative reforms is presented

A deep‐learning model to predict thunderstorms within 400 km 2

A deep-learning neural network (DLNN) model was developed to predict thunderstorm occurrence within 400 km2 South Texas domains for up to 15 hr (±2 hr accuracy) in advance. The input features were chosen primarily from numerical weather prediction model output parameters/variables; cloud-to-ground lightning served as the target. The deep-learning technique used was the stacked denoising autoencoder (SDAE) in order to create a higher order representation of the features. Logistic regression was then applied to the SDAE output to train the predictive model. An iterative technique was used to determine the optimal SDAE architecture. The performance of the optimized DLNN classifiers exceeded that of the corresponding shallow neural network models, a classifier via a combination of principal component analysis and logistic regression, and operational weather forecasters, based on the same data set.A deep-learning neural network (DLNN) model was developed to predict thunderstorm occurrence within 400 km2 South Texas domains for up to 15 hr (±2 hr accuracy) in advance. The input features were chosen primarily from numerical weather prediction model output parameters/variables; cloud-to-ground lightning served as the target. The deep-learning technique used was the stacked denoising autoencoder (SDAE) in order to create a higher order representation of the features. Logistic regression was then applied to the SDAE output to train the predictive model. An iterative technique was used to determine the optimal SDAE architecture. The performance of the optimized DLNN classifiers exceeded that of the corresponding shallow neural network models, a classifier via a combination of principal component analysis and logistic regression, and operational weather forecasters, based on the same data set

Primary Analysis of a Phase II Randomized Trial Radiation Therapy Oncology Group (RTOG) 0212: Impact of Different Total Doses and Schedules of Prophylactic Cranial Irradiation on Chronic Neurotoxicity and Quality of Life for Patients With Limited-Disease Small-Cell Lung Cancer

To determine the effect of dose and fractionation schedule of prophylactic cranial irradiation (PCI) on the incidence of chronic neurotoxicity (CNt) and changes in quality of life for selected patients with limited-disease small-cell lung cancer (LD SCLC). Patients with LD SCLC who achieved a complete response after chemotherapy and thoracic irradiation were eligible for randomization to undergo PCI to a total dose of 25 Gy in 10 daily fractions (Arm 1) vs. the experimental cohort of 36 Gy. Those receiving 36 Gy underwent a secondary randomization between daily 18 fractions (Arm 2) and twice-daily 24 fractions (Arm 3). Enrolled patients participated in baseline and follow-up neuropsychological test batteries along with quality-of-life assessments. A total of 265 patients were accrued, with 131 in Arm 1, 67 in Arm 2, and 66 in Arm 3 being eligible. There are 112 patients (42.2%) alive with 25.3 months of median follow-up. There were no significant baseline differences among groups regarding quality-of-life measures and one of the neuropsychological tests, namely the Hopkins Verbal Learning Test. However, at 12 months after PCI there was a significant increase in the occurrence of CNt in the 36-Gy cohort ( p = 0.02). Logistic regression analysis revealed increasing age to be the most significant predictor of CNt ( p = 0.005). Because of the increased risk of developing CNt in study patients with 36 Gy, a total PCI dose of 25 Gy remains the standard of care for patients with LD SCLC attaining a complete response to initial chemoradiation