Salinity effects on germination and seedlings biomass of Pachycereus pecten-aboriginum: an endangered species

ABSTRACT Cacti are particularly sensitive to habitat disturbance since they have slow growth and a long life cycle. Their development and establishment depend on several factors, including environmental requirements for germination and establishment of seedlings. Two of the most influential factors are soil and water salinity. The objective of this study was to quantify seeds germination and seedling biomass production of the Aborigine's comb cactus (Pachycerus pecten-aboriginum) in salt stress using sodium chloride (NaCl) as the main salt source. The experiment was arranged in a completely randomized design using six salt levels (0.11, 2.03, 4.00, 6.03, 8.03 and 10.07 dS m -1 ) with five replicates of 20 seeds each one. The seeds were collected in a wild population of P. pecten-aboriginum in Ejido Álvaro Obregón, Baja California Sur, Mexico in June 2011. The results showed that germination and seedling biomass were significantly affected by salt stress, which was higher at 2.03 and 0.11 dS m . It is concluded that saline levels using sodium chloride as the main source of salt, affect seed germination and seedling biomass production of P. pecten-aboriginum significantly

Continuous cultivation of photosynthetic microorganisms: approaches, applications and future trends

The possibility of using photosynthetic microorganisms, such as cyanobacteria and microalgae, for converting light and carbon dioxide into valuable biochemical products has raised the need for new cost-efficient processes ensuring a constant product quality. Food, feed, biofuels, cosmetics and pharmaceutics are among the sectors that can profit from the application of photosynthetic microorganisms. Biomass growth in a photobioreactor is a complex process influenced by multiple parameters, such as photosynthetic light capture and attenuation, nutrient uptake, photobioreactor hydrodynamics and gas-liquid mass transfer. In order to optimize productivity while keeping a standard product quality, a permanent control of the main cultivation parameters is necessary, where the continuous cultivation has shown to be the best option. However it is of utmost importance to recognize the singularity of continuous cultivation of cyanobacteria and microalgae due to their dependence on light availability and intensity. In this sense, this review provides comprehensive information on recent breakthroughs and possible future trends regarding technological and process improvements in continuous cultivation systems of microalgae and cyanobacteria, that will directly affect cost-effectiveness and product quality standardization. An overview of the various applications, techniques and equipment (with special emphasis on photobioreactors) in continuous cultivation of microalgae and cyanobacteria are presented. Additionally, mathematical modelling, feasibility, economics as well as the applicability of continuous cultivation into large-scale operation, are discussed.This research work was supported by the grant SFRH/BPD/98694/2013 (Bruno Fernandes) from Fundacao para a Ciencia e a Tecnologia (Portugal). The authors thank the FCT Strategic Project PEst-OE/EQB/LA0023/2013. The authors also thank the Project "BioInd Biotechnology and Bioengineering for improved Industrial and Agro-Food processes, REF. NORTE-07-0124-FEDER-000028" Co-funded by the Programa Operacional Regional do Norte (ON.2-O Novo Norte), QREN, FEDE

Effect of Hydropriming and Biopriming on Seed Germination and Growth of Two Mexican Fir Tree Species in Danger of Extinction

Abies spp. in general have been shown to need a period of cold stratification to break dormancy and germinate, but this can be very time consuming. In this study, hydropriming by itself and in combination with biopriming was carried out on Abies hickelii and Abies religiosa seeds. For biopriming, three species of plant growth promoting rhizobacteria ( Pseudomonas fluorescens, P. putida and Bacillus subtilis) were tested. The purpose was to determine if germination and growth could be improved for these two endangered species. Our results demonstrated that treating A. hickelii and A. religiosa with both hydropriming and biopriming with certain strains of Plant Growth-Promoting Rhizobacteria (PGPR) could improve germination rates up to 91% for A. hickelii and up to 68% for A. religiosa. Importantly, these treatments showed no significant negative impact on the growth of A. religiosa and actually improved growth in A. hickelii. The application of both hydropriming and biopriming offer possibly an alternative methodology to improve germination, survival and preservation of these fir tree species of Mexico that are at risk of extinction

Mean fresh weight values of the interaction of NaCl×tissue of total protein, proline, and PEP-case activity of <i>Aloe vera</i> L. plants subjected to NaCl (mM) stress.

<p>Values within the same columns with same letters are not significantly different at <i>P</i>≤0.05 (Tukeýs HSD multiple range test).</p

Mean values of dry weight (mg g⁻¹) of the effect of NaCl (mM) in the mineral content of roots, stems, leaves and sprouts of <i>Aloe vera</i> L. plants subjected to saline stress.

<p>Values within the same columns with same letters are not significantly different at <i>P</i>≤0.05 (Tukey's HSD multiple range test).</p

Radiative habitable zones in martian polar environments

The biologically damaging solar ultraviolet (UV) radiation (quantified by the DNA-weighted dose) reaches the martian surface in extremely high levels. Searching for potentially habitable UV-protected environments on Mars, we considered the polar ice caps that consist of a seasonally varying CO2 ice cover and a permanent H2O ice layer. It was found that, though the CO2 ice is insufficient by itself to screen the UV radiation, at ~1 m depth within the perennial H2O ice the DNA-weighted dose is reduced to terrestrial levels. This depth depends strongly on the optical properties of the H2O ice layers (for instance snow-like layers). The Earth-like DNA-weighted dose and Photosynthetically Active Radiation (PAR) requirements were used to define the upper and lower limits of the northern and southern polar Radiative Habitable Zone (RHZ) for which a temporal and spatial mapping was performed. Based on these studies we conclude that photosynthetic life might be possible within the ice layers of the polar regions. The thickness varies along each martian polar spring and summer between ~1.5 and 2.4 m for H2O ice-like layers, and a few centimeters for snow-like covers. These martian Earth-like radiative habitable environments may be primary targets for future martian astrobiological missions. Special attention should be paid to planetary protection, since the polar RHZ may also be subject to terrestrial contamination by probes