Simulating spray deposition on plant canopies within a wind tunnel

Three-dimensional computer modelling techniques are being used to develop a probabilistic model of turbulence-related spray transport around various plant architectures to investigate the influence of plant architectures and crop geometry on the sprayapplication process. Plant architecture models that utilise a set of growth rules expressed in the Lindenmayer systems (L-systems) formalism have been developed and programmed using L-studio software. Modules have been added to simulate the movement ofdroplets through the air and deposition on the plant canopy. Deposition of spray on an artificial plant structure was measured in the wind tunnel at the University of Queensland, Gatton campus and the results compared to the model simulation. Further trials are planned to measure the deposition of spray droplets on various crop and weed species and the results from these trials will be used to refine and validate the combined spray and plant architecture model.

A model of macadamia with application to pruning in orchards

A self-organising model of macadamia, expressed using L-Systems, was used to explore aspects of canopy management. A small set of parameters control the basic architecture of the model, with a high degree of self-organisation occurring to determine the fate and growth of buds. Light was sensed at the leaf level and used to represent vigour and accumulated basipetally. Buds also sensed light so as to provide demand in the subsequent redistribution of the vigour. Empirical relationships were derived from a set of 24 completely digitised trees after conversion to multiscale tree graphs (MTG) and analysis with the OpenAlea software library. The ability to write MTG files was embedded within the model so that various tree statistics could be exported for each run of the model. To explore the parameter space a series of runs was completed using a high-throughput computing platform. When combined with MTG generation and analysis with OpenAlea it provided a convenient way in which thousands of simulations could be explored. We allowed the model trees to develop using self-organisation and simulated cultural practices such as hedging, topping, removal of the leader and limb removal within a small representation of an orchard. The model provides insight into the impact of these practices on potential for growth and the light distribution within the canopy and to the orchard floor by coupling the model with a path-tracing program to simulate the light environment. The lessons learnt from this will be applied to other evergreen, tropical fruit and nut trees.

Characterization of sour (Prunus cerasus L.) and sweet cherry (Prunus avium L.) varieties with five isozyme systems

Extracts from young leaves of nine sweet cherry (Prunus avium L.) and eight sour cherry (Prunus cerasus L.) varieties, located in the germplasm collection of the 'Direção Regional de Agricultura da Beira Interior' (Fundão, Portugal), were analysed for five isozyme systems in order to characterise these varieties and detect problems of synonymies and homonymies that frequently present. The sweet and sour cherry varieties analyzed showed low isoenzymatic polymorphism, being PGM and PGI the systems with the highest discrimination power. These systems presented seven and five different zymogrames, respectively. IDH showed four patterns. SKDH and 6-PGD grouped the varieties only into two patterns. The evident and discriminant restrictions of this type of analysis had got results that have only been a complement for agronomical and morphological characterization.

Investigation of cytotoxic and mutagenic effects of Malpighia glabra L. (barbados cherry) fruit pulp and vitamin C on plant and animal test systems

Fruits are important sources of nutrients in human diet, and Barbados Cherry (Malpighia glabra L.) is of particular interest due to its high content of antioxidants. Diets rich in fruits and vegetables protect individuals against diseases and cancer, but excessive intake of vitamins may act as pro-oxidant and generate changes in DNA. To evaluate the effect of different in natura (BAN) and frozen (BAF) Barbados Cherry pulp concentrations and synthetic vitamin C in liquid form (VC) on the chromosome level and the cell cycle division, root meristeme cells of Allium cepa L. and bone marrow cells of Wistar rats Rattus norvegicus, were used as test system. In Allium cepa L., BAN, at the highest concentration (0.4 mg.mL-1) and BAF, at the lowest concentration (0.2 mg.mL-1), inhibited cell division, and there was recovery of cell division after the recovery period in water only for BAN. In the Wistar rats, all treatments with Barbados Cherry, either acute or subchronic, were not cytotoxic or mutagenic; only the highest concentration of VC increased significantly the rate of chromosomal abnormalities. The data obtained are important to reinforce the use of Barbados Cherry fruit in the diet.

Evaluation of in vitro resistance of titanium and resorbable (poly-L-DL-lactic acid) fixation systems on the mandibular angle fracture

The purpose of this study was to compare, by mechanical in vitro testing, a 2.0-mm system made with poly-L-DL-lactide acid with an analogue titanium-based system. Mandible replicas were used as a substrate and uniformly sectioned on the left mandibular angle. The 4-hole plates were adapted and stabilized passively in the same site in both groups using four screws, 6.0 mm long. During the resistance-to-load test, the force was applied perpendicular to the occlusal plane at three different points: first molar at the plated side; first molar at the contralateral side; and between the central incisors. At 1 mm of displacement, no statistically significant difference was found. At 2 mm displacement, a statistically significant difference was observed when an unfavourable fracture was simulated and the load was applied in the contralateral first molar and when a favourable fracture was simulated and the load was applied between the central incisors. At the failure displacement, a statistically significant difference was observed only when the favourable fracture was simulated and the load was applied on the first molar at the plated side. In conclusion, despite more failure, the poly-L-DL-lactic acid-based system was effective.

Determination of the antimutagenicity of an aqueous extract of Rhizophora mangle L. (Rhizophoraceae), using in vivo and in vitro test systems

An aqueous extract of Rhizophora mangle L. bark is used as raw material in pottery making in the State of Espirito Santo, Brazil. This extract presents large quantities of tannins, compounds possessing antioxidant properties. Tannin antioxidant activity, as a plant chemical defense mechanism in the process of stabilizing free radicals, has been an incentive to studies on anti-mutagenicity. The present work aimed to evaluate possible antimutagenic activity of a R. mangle aqueous extract, using the Allium cepa test-system and micronuclear (MN) assay with blockage of cytokinesis in Chinese hamster ovary cells (CHO-K1). The Allium cepa test-system indicated antimutagenic activity against the damage induced by the mutagenic agent methyl methanesulfonate. A reduction in both MN cell frequency and chromosome breaks occurred in both the pre and post-treatment protocols. The MN testing of CHO-K1 cells revealed anti-mutagenic activity of the R. mangle extract against methyl methanesulfonate and doxorubicin in pre, simultaneous and post-treatment protocols. These results suggest the presence of phyto-constituents in the extract presenting demutagenic and bio-antimutagenic activities. Since the chemical constitution of Rhizophora mangle species presents elevated tannin content, it is highly probable that these compounds are the antimutagenic promoters themselves.

Pluronics F-127/L-81 Binary Hydrogels as Drug-Delivery Systems: Influence of Physicochemical Aspects on Release Kinetics and Cytotoxicity

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Acute stress regulates vasotocinergic and isotocinergic systems in the gilthead sea bream (Sparus aurata L.).

The hypothalamus-pituitary-interrenal axis is involved in stress response regulation. In addition, arginine vasotocin (AVT) and isotocin (IT) are also considered as important players in this stress regulation. The present study assessed, using the teleost gilthead sea bream (Sparus aurata) as a biological model, hypothalamic mRNA expression changes of AVT and IT and their receptors at hepatic level after an acute stress situation. Specimens were submitted to air for 3 min and place back in their respective tanks after that, being sampled at different times (15 min, 30 min, 1, 2, 4 and 8 hours post-stress) in order to study the time course response. Plasma cortisol values increased after few minutes post-exposure, decreasing during the experimental time while a metabolic reorganization occurred in both plasmatic and hepatic levels. At hypothalamic level, acute stress affects mRNA expression of AVT and IT precursors, as well as hepatic expression of their receptors, suggesting the involvement of both vasotocinergic and isotocinergic systems in the acute stress response. Our results demonstrate the activation and involvement of both endocrine pathways in the regulation of metabolic and stress systems of Sparus aurata, which is stated, at least, through changes in mRNA expression levels of these genes analysed.