Cyclic Variations in Plant Properties under Constant Environmental Conditions

Cyclic fluctuations in stomatal aperture, transpiration rate and leaf water potential under constant environmental conditions have been investigated in intact plants of cotton, pepper, and sunflower. Stomatal aperture and transpiration rate were least when leaf water potential was high and were greatest when leaf water potential was low. Lowest leaf water potential values lagged behind the occurrence of highest transpiration rates, and high overall resistance to water flow occurred in cycling plants. Both of these are considered essential for the occurrence of persistent cyclic behaviour. Hydropassive opening of stomates as the leaves wilted facilitated cycling in cotton and pepper, but not in sunflower, where hydropassive opening did not occur. The roots were identified as the site of the major resistance to water flow in the plant and further experiments directly showed the importance of this root resistance in initiating cycling by causing water stress in the leaves as the stomates opened. Root resistance varied diurnally, becoming increasingly important at night. Root resistance naturally rose to high levels in cotton. High levels were induced in pepper or sunflower by having the roots in deionized water for several days or by anoxia. Quantitative measurements of overall plant resistance were made from leaf water potential and transpiration rate data. The results are discussed and it suggested that plant resistance may indirectly be of importance in the movement of water from the plant to the air.     

Oxygen Productivity of Planktonic Algae under Fluctuating and Constant Light Conditions

Net oxygen productivity in cultures of Monoraphidium minutum, Cryptomonas sp. and Planktothrix agardhii exposed to fluctuating and constant light conditions was measured in a laboratory incubator. The fluctuating light climate simulated a linear up and down movement in a 2 m water column at 4 different ratios of euphotic depth to mixing depth. In addition, cultures were kept at a constant light climate simulating static incubation at 0, 0.5, 1 and 2 m depth and at the depth of the mean irradiance, respectively. Integral productivity in the simulated water column was lowest when algae were incubated at constant light in different depths, highest when the algae were incubated at constant mean photon flux density (PFD) and intermediate under fluctuating light. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Rhythmic Conidiation in Constant Light in Vivid Mutants of Neurospora crassa

In Neurospora crassa, a circadian rhythm of conidiation (asexual spore formation) can be seen on the surface of agar media. This rhythm has a period of 22 hr in constant darkness (D/D). Under constant illumination (L/L), no rhythm is visible and cultures show constant conidiation. However, here we report that strains with a mutation in the vivid (vvd) gene, previously shown to code for the photoreceptor involved in photo-adaptation, exhibit conidiation rhythms in L/L as well as in D/D. The period of the rhythm of vvd strains ranges between 6 and 21 hr in L/L, depending upon the intensity of the light, the carbon source, and the presence of other mutations. Temperature compensation of the period also depends on light intensity. Dark pulses given in L/L shift the phase of the rhythm. Shifts from L/L to D/D show unexpected after effects; i.e., the short period of a vvd strain in L/L gradually lengthens over 2–3 days in D/D. The rhythm in L/L requires the white collar (wc-1) gene, but not the frequency (frq) gene. FRQ protein shows no rhythm in L/L in a vvd strain. The conidiation rhythm in L/L in vvd is therefore driven by a FRQ-less oscillator (FLO).     

The Growth of Scions under Conditions of Extreme Vigour

In order to ascertain growth-rates of scions free from rootstocklimitations, shoot- and root-scions were induced to grow veryrapidly by grafting them on to heavily pruned rootstocks. Underthese conditions the growth-rates of shoot-scions did not followthe same order as the root-scions of the same varieties; thegrowth-rates of root and shoot scions relative to one anotherwere in accordance with the hypothesis that the growth-rateof a composite tree wan the resultant of the growth-rates ofits component varieties. Varietali differences in shoot weightwere attributable largely to differences in the proportion ofleafage on the shoots, average increments in shoot weight pergram of leaf being nearly the aame for all varieties; withinvarieties, the lighter shoots had less increment per gram ofleaf than the heavier, despite, in some cases, a higher proportionof leafage.     

Oligotrophic Bacteria Enhance Algal Growth under Iron-Deficient Conditions

A Halomonas sp., a marine halophilic and oligotrophic bacterium, was grown on exudates of Dunaliella bardawil. The bacteria increased the solubility of Fe, thereby enhancing its availability to the algae. As a result, the algal growth rate increased. Because of these syntrophic relations, growth of the marine alga D. bardawil was facilitated at Fe levels that would otherwise induce Fe deficiency and inhibit algal growth.     

Rhythmic Excitation in Nitella at Conditions of Voltage Clamp

Rhythmic excitation of Nitella cells initiated in 100 mM NaCloccurred when the voltage across the plasmalemma was fixed notonly at the resting level, but also at different hyperpolarizedlevels. The results presented indicate that the activation ofthe excitable units is not potential-dependent but is insteadchemical, reflecting changes in the ionic status within themembrane. Key words: Nitella, Plasmalemma potential difference, Rhythmic excitation     

Growth of Peach Plants under Different Filtered Sunlight Conditions

Young peach plants (Prunus persica) were grown outdoors under different colored filters, to examine the effect of light quality on plant behavior. It was found that under blue light growth rate, leaf size and number, rate of spring bud opening and secondary branching were very similar to control plants grown under neutral shade. Blue + far-red light showed an overall strong inhibitory effect on all these characteristics. Red + far-red light produced the strongest growth activity with best results in growth rate and leaf size and number. The phytochrome pigment system was suggested to be the only pigment regulating growth under high light intensities. Blue and blue + far-red light acted antagonistically on apical dominance features of the tree. The former produced a wider tree with nearly horizontal shoots, while the latter produced a more erect narrow tree.     

Characterization of Campylobacter jejuni Biofilms under Defined Growth Conditions

Campylobacter jejuni is a major cause of human diarrheal disease in many industrialized countries and is a source of public health and economic burden. C. jejuni, present as normal flora in the intestinal tract of commercial broiler chickens and other livestock, is probably the main source of human infections. The presence of C. jejuni in biofilms found in animal production watering systems may play a role in the colonization of these animals. We have determined that C. jejuni can form biofilms on a variety of abiotic surfaces commonly used in watering systems, such as acrylonitrile butadiene styrene and polyvinyl chloride plastics. Furthermore, C. jejuni biofilm formation was inhibited by growth in nutrient-rich media or high osmolarity, and thermophilic and microaerophilic conditions enhanced biofilm formation. Thus, nutritional and environmental conditions affect the formation of C. jejuni biofilms. Both flagella and quorum sensing appear to be required for maximal biofilm formation, as C. jejuni flaAB and luxS mutants were significantly reduced in their ability to form biofilms compared to the wild-type strain.     

Rhythmic Growth in Excised Sprout-leaves of Onion Bulbs

Sprout leaf preparations, consisted of the inner 6 or 7 sprout leaves attached to the base plate of bulbs of Allium cepa cv. Downy Yellow Globe. The preparations excised from dormant bulbs were capable of sprouting. The elongation of the sprout leaves in the light was inhibited by a field pretreatment of 2000 mg/1 M.H.-30 (30% maleic hydrazide) and stimulated by incubation in the dark. Rapid cooling of the bulbs prior to excising of the preparations had no effect on sprouting. The ability of the sprout leaf preparations to elongate followed a cyclical time course, displaying maxima 8 to 12 weeks apart. Pretreatment with M.H.-30 inhibited this periodicity.     

Turnover of Phospholipids in Bacillus cereus under Various Growth Conditions

As a search for natural antioxidants from plant materials, strong antioxidative activity was observed in leaf waxes extracted from Eucalyptus species. A novel type of antioxidant was isolated from the leaf wax of Eucalyptus globulus and identified as n-tritriacontan-16,18-dione. Antioxidative activities were determined by different methods; a thiocyanate method, a thiobarbituric acid method, a total carbonyl value method and a weighing test. The anti-oxidant showed remarkable antioxidative activity in a water/alcohol system and was more effective than α-tocopherol and BHA; however, it has no antioxidative activity in an oil system.     

Survival and Growth of Tree Species under Two Direct Seedling Planting Systems

Direct tree planting restoration systems are frequently used for recovering degraded tropical landscapes. Although manual planting tends to be more viable economically and logistically over small areas, in large restorations the use of agricultural equipment that optimizes effort is preferable. The aim of this study was to investigate the efficiency of the two native tree species planting systems—manual and mechanized—used in the restoration of Atlantic Forest landscapes that have been converted to pasture. In recently abandoned grazing areas with abundant cover of the exotic grass Brachiaria humidicola, 393 seedlings of 6 species were planted in two treatments: a mechanized planting system (soil prepared with a rotary tiller attached to a tractor; seedlings in polypropylene tubes) and a manual planting system (holes dug with a manual excavator; seedlings wrapped in polyethylene bags). After 12 months, survival (manual: 85%; mechanized: 71%) and growth rates (RGR_height: manual = 0.88 ± 0.06 and mechanized = 0.98 ± 0.06 cm/cm; RGR_diameter: manual = 0.77 ± 0.05 and mechanized = 0.86 ± 0.05 cm/cm) were high in both treatments, but no differences were found between them. Both planting systems proved efficient for planting native tree seedlings in pastures. The excellent results demonstrated in this study by the mechanized planting system are important because this cheap and readily available technique provides a good, but less frequently used, alternative to the manual planting system.     

Metabolite Profiling Uncovers Plasmid-Induced Cobalt Limitation under Methylotrophic Growth Conditions

Background

The introduction and maintenance of plasmids in cells is often associated with a reduction of growth rate. The reason for this growth reduction is unclear in many cases.

Methodology/Principal Findings

We observed a surprisingly large reduction in growth rate of about 50% of Methylobacterium extorquens AM1 during methylotrophic growth in the presence of a plasmid, pCM80 expressing the tetA gene, relative to the wild-type. A less pronounced growth delay during growth under non-methylotrophic growth conditions was observed; this suggested an inhibition of one-carbon metabolism rather than a general growth inhibition or metabolic burden. Metabolome analyses revealed an increase in pool sizes of ethylmalonyl-CoA and methylmalonyl-CoA of more than 6- and 35-fold, respectively, relative to wild type, suggesting a strongly reduced conversion of these central intermediates, which are essential for glyoxylate regeneration in this model methylotroph. Similar results were found for M. extorquens AM1 pCM160 which confers kanamycin resistance. These intermediates of the ethylmalonyl-CoA pathway have in common their conversion by coenzyme B₁₂-dependent mutases, which have cobalt as a central ligand. The one-carbon metabolism-related growth delay was restored by providing higher cobalt concentrations, by heterologous expression of isocitrate lyase as an alternative path for glyoxylate regeneration, or by identification and overproduction of proteins involved in cobalt import.

Conclusions/Significance

This study demonstrates that the introduction of the plasmids leads to an apparent inhibition of the cobalt-dependent enzymes of the ethylmalonyl-CoA pathway. Possible explanations are presented and point to a limited cobalt concentration in the cell as a consequence of the antibiotic stress.     

Interaction of Lactic Acid Bacteria under Different Conditions of Combined Growth

Biology Bulletin - In order to obtain starter cultures for new fermented milk products, the influence of growing conditions (temperature, the ratio of the number of lactic acid bacteria introduced...     

四种热带雨林树种光合和形态解剖特征对不同生长光强的适应

研究了西双版纳热带雨林2种喜光树种中平树(Macaranga denticulata)、倒樱木(Pnravallaris macrophylla)和2种耐荫树种云南肉豆蔻(Myristica yunnanensis)、金丝李(Garcinia paucinervis)幼苗叶片光合和形态解剖特征对3种不同生长光强(5％、25%和50％相对光强)的适应。研究结果表明,与强光下相比,弱光下生长的4种植物最大净光合速率、光饱和点、光补偿点、暗呼吸速率、叶绿素a／b、叶片和栅栏组织厚度、气孔密度和比叶重都降低,而海绵组织／栅栏组织和叶绿素含量升高。在相同光强下,与2种耐荫树种相比,2种喜光树种有较大的最大净光合速率、暗呼吸速率、气孔密度和较低的叶绿素含量。在不同光强下,4种植物均表现出了对光适应有利的生理和形态解剖可塑性,而喜光树种比耐荫树种有较大的生理和形态可塑性,表明喜光树种具有比耐荫树种对强光有更强的适应能力。4种植物的生理指标的可塑性均大于叶片解剖结构的可塑性。