Effects of Zn Deficiency and Bicarbonate on the Growth and Photosynthetic Characteristics of Four Plant Species.

Calcareous soils are characterized by low nutrient contents, high bicarbonate (HCO3-) content, and high alkalinity. The effects of HCO3- addition under zinc-sufficient (+Zn) and zinc-deficient (-Zn) conditions on the growth and photosynthetic characteristics of seedlings of two Moraceae species (Broussonetia papyrifera and Morus alba) and two Brassicaceae species (Orychophragmus violaceus and Brassica napus) were investigated. These four species were hydroponically grown in nutrient solution with 0 mM Zn (-Zn) or 0.02 mM Zn (+Zn) and 0 mM or 10 mM HCO3-. The photosynthetic response to HCO3- treatment, Zn deficiency, or both varied according to plant species. Of the four species, Broussonetia papyrifera showed the best adaptability to Zn deficiency for both the 0 mM and 10 mM HCO3- treatments due to its strong growth and minimal inhibition of photosynthesis and photosystem II (PS II). Brassica napus was sensitive to Zn deficiency, HCO3- treatment, or both as evidenced by the considerable inhibition of photosynthesis and high PS II activity. The results indicated different responses of various plant species to Zn deficiency and excess HCO3-. Broussonetia papyrifera was shown to have potential as a pioneer species in karst regions.

Anti-inflammatory and anticholinesterase activity of six flavonoids isolated from Polygonum and Dorstenia species.

This study was aimed at investigating the anti-inflammatory and anticholinesterase activity of six naturally occurring flavonoids: (-) pinostrobin (1), 2',4'-dihydroxy-3',6'-dimethoxychalcone (2), 6-8-diprenyleriodictyol (3), isobavachalcone (4), 4-hydroxylonchocarpin (5) and 6-prenylapigenin (6). These compounds were isolated from Dorstenia and Polygonum species used traditionally to treat pain. The anti-inflammatory activity was determined by using the Griess assay and the 15-lipoxygenase inhibitory activity was determined with the ferrous oxidation-xylenol orange assay. Acetylcholinesterase inhibition was determined by the Ellman's method. At the lowest concentration tested (3.12 µg/ml), compounds 2, 3 and 4 had significant NO inhibitory activity with 90.71, 84.65 and 79.57 % inhibition respectively compared to the positive control quercetin (67.93 %). At this concentration there was no significant cytotoxicity against macrophages with 91.67, 72.86 and 70.86 % cell viability respectively, compared to 73.1 % for quercetin. Compound 4 had the most potent lipoxygenase inhibitory activity (IC50 of 25.92 µg/ml). With the exception of (-) pinostrobin (1), all the flavonoids had selective anticholinesterase activity with IC50 values ranging between 5.93 and 8.76 µg/ml compared to the IC50 4.94 µg/ml of eserine the positive control. These results indicate that the studied flavonoids especially isobavachalcone are potential anti-inflammatory natural products that may have the potential to be developed as therapeutic agents against inflammatory conditions and even Alzheimer's disease.

New Insights on Wood Dimensional Stability Influenced by Secondary Metabolites: The Case of a Fast-Growing Tropical Species Bagassa guianensis Aubl.

Challenging evaluation of tropical forest biodiversity requires the reporting of taxonomic diversity but also the systematic characterization of wood properties in order to discover new promising species for timber industry. Among wood properties, the dimensional stability is regarded as a major technological characteristic to validate whether a wood species is adapted to commercial uses. Cell structure and organization are known to influence the drying shrinkage making wood density and microfibrils angle markers of choice to predict wood dimensional stability. On the contrary the role of wood extractive content remains unclear. This work focuses on the fast-growing tropical species Bagassa guianensis and we report herein a correlation between heartwood drying shrinkage and extractive content. Chemical extractions and shrinkage experiments were performed on separate wood twin samples to better evaluate correctly how secondary metabolites influence the wood shrinkage behaviour. Extractive content were qualitatively and quantitatively analysed using HPLC and NMR spectroscopy. We found that B guianensis heartwood has a homogeneous low shrinkage along its radius that could not be explained only by its basic density. In fact the low drying shrinkage is correlated to the high extractive content and a corrected model to improve the prediction of wood dimensional stability is presented. Additionally NMR experiments conducted on sapwood and heartwood extracts demonstrate that secondary metabolites biosynthesis occurs in sapwood thus revealing B. guianensis as a Juglans-Type heartwood formation. This work demonstrates that B. guianensis, a fast-growing species associated with high durability and high dimensional stability, is a good candidate for lumber production and commercial purposes.

The effect of bovine milk on the growth of Bombyx mori.

Bombyx mori L. (Lepidoptera: Bombycidae) is a well-studied Lepidopteran model system because of its morphology, life cycle, and economic importance. Many scientists have placed importance on enhancing the economic traits of B. mori because it's larvae, silkworms, are vital in the production of silk. In this study, the effect of bovine milk on B. mori growth was tested. Bovine milk contains several components that aid in healthy growth. The treatment was given to fifth instar B. mori larvae because the fifth instar period is when B. mori eats voraciously and shows maximum growth among all its larval stages. The larvae were treated with fresh mulberry, Morus L. (Rosales: Moraceae), leaves and mulberry leaves dipped in milk from the first day of the fifth instar. Treatments were given on alternate days, and the silkworms were weighed every day to determine whether milk had any role in enhancing the weight of the larvae. Cocoon weights were measured, as the weight indicates the approximate amount of silk that can be reeled. The results showed that larvae gained 82.5% more weight by the end of fifth instar larval when fed with mulberry leaves dipped in milk than when fed with fresh mulberry leaves without milk. The larvae fed with milk-treated leaves gained 310% weight from day 1 to day 7 of the fifth instar, while the larvae fed with fresh leaves gained 153% weight in the same timespan. In addition, cocoon weight increased by 8% when milk was added compared to when it was not. These results suggest that B. mori larvae can be fed mulberry leaves treated with bovine milk for better growth rate and increased silk production.

Crecimiento, supervivencia y herbivoría de plántulas de Brosimum alicastrum (Moraceae), una especie del sotobosque neotropical

Growth, survival and herbivory of seedlings in Brosimum alicastrum (Moraceae), a species from the Neotropical undergrowth. Growth responses, survival, and herbivory, on seedlings of Brosimum alicastrum were studied in a neotropical Mexican forest. We selected 122 seedlings and divided them into three groups assigned to defoliation treatments: control or 0 (n=21), 50 (n=51) and 90% (n=50). Every 4 months during two years we measured seedling growth (in terms of relative growth rate in biomass, leaf area growth, produced leaves and height growth) and survival. In addition, we evaluated every 12 months pathogen damage and insect herbivory using a 2 mm-2 grid. Separately, we estimated mammal herbivory in 3-month old seedlings that were selected within a plot of 500 m x 10 m (N=1095). Pathogen damage and insect herbivory were evaluated within the same plot in 113 seedlings. We found that 50 % defoliated seedlings showed compensatory responses in all growth parameters. Relative growth rate and height growth also had a compensatory response in seedlings at 90% defoliation. Relative growth rate and leaf area growth gradually decreased with time although height growth seedling showed an opposite pattern. Leaves produced were not affected by time. Estimated seedling survival probability increased with defoliation to a maximum of 97%, decreasing at 24 month to 37%. Mammal herbivory was more frequent and severe than herbivory caused by pathogens and insects. In some cases, mammal herbivory produced total defoliation. Compensatory growth in leaf area growth, produced leaves and height growth seedling suggest a synergic compensatory mechanism expressed in a whole-plant growth biomass (relative growth rate). Compensation and survival results suggest trade-offs at the leaf level, such as leaf area growth and produced leaves versus chemical defenses, respectively. Rev. Biol. Trop. 56 (4): 2055-2067. Epub 2008 December 12.

Se estudiaron las respuestas de crecimiento, supervivencia y los diferentes tipos de herbivoría sobre plántulas de B. alicastrum en una selva neotropical de México. Se seleccionaron 122 plántulas de una población las cuales se asignaron a tres tratamientos de defoliación: control o 0% (n=21), 50% (n=51) y 90% (n=50). Cada 4 meses durante dos años se midió su crecimiento (en términos de la tasa relativa de crecimiento en biomasa, área foliar, hojas producidas y altura) y supervivencia. Además cada 12 meses, mediante el uso de una cuadricula de 2mm-2, se evaluó la herbivoría causada por patógenos e insectos. También dentro de una parcela de 500 m largo x 10 m de ancho se evaluó en 1095 plántulas de 3 meses de edad la herbivoría por mamíferos. En la misma parcela pero en 113 plántulas se estimó la herbivoría por patógenos e insectos. Las plántulas defoliadas al 50% compensaron su crecimiento en todas las estructuras medidas, pero sólo la tasa relativa de crecimiento y altura lo hicieron con la defoliación al 90%. La tasa relativa de crecimiento y el área foliar disminuyeron gradualmente con el tiempo, contrario a la altura con un patrón opuesto. El número de hojas producidas no se afectó por el tiempo. La probabilidad estimada de supervivencia incrementó hasta un 95% con la defoliación y disminuyó hasta un 37% a los 24 meses. La herbivoría por mamíferos fue el más incidente y severo, en algunos casos hasta un 100% de defoliación. En tanto la causada por patógenos e insectos fue secundaria. El crecimiento compensatorio en área foliar, producción de hojas y altura sugieren un mecanismo compensatorio sinérgico expresado a nivel del crecimiento individual de la planta (tasa de crecimiento en biomasa). Al mismo tiempo junto con la supervivencia sugiere un posible compromiso entre las respuestas de crecimiento a nivel de la hoja - área foliar y hojas producidas - versus producción de defensas químicas.

[Growth, survival and herbivory of seedlings in Brosimum alicastrum (Moraceae), a species from the Neotropical undergrowth]. / Crecimiento, supervivencia y herbivoría de plántulas de Brosimum alicastrum (Moraceae), una especie del sotobosque neotropical.

Growth responses, survival, and herbivory, on seedlings of Brosimum alicastrum were studied in a neotropical Mexican forest. We selected 122 seedlings and divided them into three groups assigned to defoliation treatments: control or 0 (n=21), 50 (n=51) and 90% (n=50). Every 4 months during two years we measured seedling growth (in terms of relative growth rate in biomass, leaf area growth, produced leaves and height growth) and survival. In addition, we evaluated every 12 months pathogen damage and insect herbivory using a 2 mm(-2) grid. Separately, we estimated mammal herbivory in 3-month old seedlings that were selected within a plot of 500 m x 10 m (N=1095). Pathogen damage and insect herbivory were evaluated within the same plot in 113 seedlings. We found that 50% defoliated seedlings showed compensatory responses in all growth parameters. Relative growth rate and height growth also had a compensatory response in seedlings at 90% defoliation. Relative growth rate and leaf area growth gradually decreased with time although height growth seedling showed an opposite pattern. Leaves produced were not affected by time. Estimated seedling survival probability increased with defoliation to a maximum of 97%, decreasing at 24 month to 37%. Mammal herbivory was more frequent and severe than herbivory caused by pathogens and insects. In some cases, mammal herbivory produced total defoliation. Compensatory growth in leaf area growth, produced leaves and height growth seedling suggest a synergic compensatory mechanism expressed in a whole-plant growth biomass (relative growth rate). Compensation and survival results suggest trade-offs at the leaf level, such as leaf area growth and produced leaves versus chemical defenses, respectively.

Relative importance of photosynthetic physiology and biomass allocation for tree seedling growth across a broad light gradient.

Studies of tree seedling physiology and growth under field conditions provide information on the mechanisms underlying inter- and intraspecific differences in growth and survival at a critical period during forest regeneration. I compared photosynthetic physiology, growth and biomass allocation in seedlings of three shade-tolerant tree species, Virola koschynii Warb., Dipteryx panamensis (Pittier) Record & Mell and Brosimum alicastrum Swartz., growing across a light gradient created by a forest-pasture edge (0.5 to 67% diffuse transmittance (%T)). Most growth and physiological traits showed nonlinear responses to light availability, with the greatest changes occurring between 0.5 and 20 %T. Specific leaf area (SLA) and nitrogen per unit leaf mass (N mass) decreased, maximum assimilation per unit leaf area (A area) and area-based leaf N concentration (N area) increased, and maximum assimilation per unit leaf mass (A mass) did not change with increasing irradiance. Plastic responses in SLA were important determinants of leaf N and A area across the gradient. Species differed in magnitude and plasticity of growth; B. alicastrum had the lowest relative growth rates (RGR) and low plasticity. Its final biomass varied only 10-fold across the light gradient. In contrast, the final biomass of D. panamensis and V. koschynii varied by 100- and 50-fold, respectively, and both had higher RGR than B. alicastrum. As light availability increased, all species decreased biomass allocation to leaf tissue (mass and area) and showed a trade-off between allocation to leaf area at a given plant mass (LAR) and net gain in mass per unit leaf area (net assimilation rate, NAR). This trade-off largely reflected declines in SLA with increasing light. Finally, A area was correlated with NAR and both were major determinants of intraspecific variation in RGR. These data indicate the importance of plasticity in photosynthetic physiology and allocation for variation in tree seedling growth among habitats that vary in light availability.

Root turnover: an important source of microbial substrates in rhizosphere remediation of recalcitrant contaminants.

The growth dynamics and phenolic content of mulberry (Morus sp.) fine roots (<1 mm diameter) were determined and examined in relationship to rhizosphere remediation of recalcitrant soil contaminants. Root turnover measurements of rhizotron-grown plants showed that 58% of the fine roots produced during a 6-month growing season (June-November) died at the end of the season. The concentration of phenolic compounds in fine roots increased approximately 2-fold during the later stages of the season, and the total phenolic content of dead fine roots reached a maximum value of 38 mg/g dry weight. The late-season increase in total phenolics was primarily due to accumulation of three different flavones (morusin, morusinol, and kuwanon C). These three flavones were shown to support the growth of the bacterium Burkholderia sp. LB400, a degrader of polychlorinated biphenyls (PCBs). Thus, it has been established that, upon death, the fine roots of mulberry can serve as a source of substrate for PCB-degrading bacteria. These results establish for the first time that the chemical content and turnover rate of fine roots should be considered an important aspect of rhizosphere remediation.