Vegetative Plant Growth Analysis in Controlled Environments

Current techniques for analysing growth are compared using datafrom young plants grown in artificially-lit growth cabinets.A statistical method of fitting curves to log dry weight andlog leaf areas led to values which often diverged from biologicalexpectation. It was more satisfactory to make the calculationsassuming that a quadratic relation always applied. It appears that the statistical methods cannot be used unmodifiedfor experiments involving comparisons between artificially-litcabinets. Cabinet environments are seldom replicated and thereforethe consequences of isolated anomalies in either the environmentor in a particular harvest are not allowed for and are reproducedin the final curves. In addition the statistical method assumesthat all the growth curves are entirely independent, whereasthere is a tendency for the opposite to be true.     

Photoperiod Responses of Corchorus olitorius L. in Controlled Environments

Controlled environments were used to establish the base-linegrowth and to evaluate the photoperiodic response of two Tossajute (Corchorus olitorius) cultivars. Fresh and dry weightsof shoots and roots, leaf areas and stem lengths were much greaterat long day (LD) 12·5, 11·5 than LD 11·5,12·5 photoperiods for both cultivars. Root lengths weregreater at LD 12·5, 11·5 initially but were longestat LD 11·5, 12·5 at 35 days from emergence. Meanrelative growth rates (MRGR) were similar irrespective of photoperiodor cultivar but declined with plant age. The superior growthof cultivar ‘Yaya’ at LD 12·5, 11·5was due to more growth in the first 7 days, while, for cultivar‘Angbadu’ it was a combination of growth for 7 days,and higher MRGR up to 21 days. Stomatal density was greaterat LD 12·5, 11·5 than LD 11·5, 12·5. Corchorus olitorius L., Tossa jute, photoperiodism, relative growth rate     

Stress: a Factor to be Considered in Heterotrophic Microorganism Enumeration from Aquatic Environments

Heterotrophic microorganisms in water samples are susceptible to the transient stress of warmed agar used in the standard methods pour plate procedure, causing significantly decreased recoveries in comparison with a spread plate technique. Microbial starvation can increase susceptibility to a transient warming stress. The standard plate count procedure, as presently described, should not be considered for quantitation of microorganisms from aquatic environments.     

Telomerase as a Growth-Promoting Factor

Beyond its role in telomere maintenance, telomerase provides additional functions in tumorogenesis, DNA repair, and cell survival. Telomerase protects cells from apoptosis and necrosis, and stimulates growth in adverse conditions. Furthermore, gross overexpression of the catalytic subunit of telomerase (hTERT) may act as a hyperproliferative signal to induce a senescence-like phenotype in normal fibroblasts, which is similar to the senescence induced by overexpression of oncogenes. As some of these functions can be dissociated from telomere lengthening, the question arises as to how the mere presence of telomerase can serve as a survival and growth-promoting factor.     

Flowering of Contrasting White Clover Varieties in Relation to Temperature in Controlled Environments

Effects of temperature on floral initiation of ten white clovervarieties growing in controlled environments are described.Plants grown under long days (16 h) were subjected to constanttemperatures of 26, 18 and 10 ^°C. Relationships betweenmorphological and physiological traits and flowering were examined. Most plants flowered at the two higher temperatures but only10 per cent of plants flowered at 10 ^°C. Larger leaved typestended to produce more reproductive buds per stolon at the highertemperatures than did smaller leaved varieties. Of the floral characters studied, floret number was least affectedby temperature. Ovule number and peduncle length were greatestat 18 ^°C. Variation in, and absolute level of nectar secretionwas greatest at the highest temperature. Trifolium repens, white clover, flowering, temperature     

The Repertoire and Dynamics of Evolutionary Adaptations to Controlled Nutrient-Limited Environments in Yeast

The experimental evolution of laboratory populations of microbes provides an opportunity to observe the evolutionary dynamics of adaptation in real time. Until very recently, however, such studies have been limited by our inability to systematically find mutations in evolved organisms. We overcome this limitation by using a variety of DNA microarray-based techniques to characterize genetic changes—including point mutations, structural changes, and insertion variation—that resulted from the experimental adaptation of 24 haploid and diploid cultures of Saccharomyces cerevisiae to growth in either glucose, sulfate, or phosphate-limited chemostats for ∼200 generations. We identified frequent genomic amplifications and rearrangements as well as novel retrotransposition events associated with adaptation. Global nucleotide variation detection in ten clonal isolates identified 32 point mutations. On the basis of mutation frequencies, we infer that these mutations and the subsequent dynamics of adaptation are determined by the batch phase of growth prior to initiation of the continuous phase in the chemostat. We relate these genotypic changes to phenotypic outcomes, namely global patterns of gene expression, and to increases in fitness by 5–50%. We found that the spectrum of available mutations in glucose- or phosphate-limited environments combined with the batch phase population dynamics early in our experiments allowed several distinct genotypic and phenotypic evolutionary pathways in response to these nutrient limitations. By contrast, sulfate-limited populations were much more constrained in both genotypic and phenotypic outcomes. Thus, the reproducibility of evolution varies with specific selective pressures, reflecting the constraints inherent in the system-level organization of metabolic processes in the cell. We were able to relate some of the observed adaptive mutations (e.g., transporter gene amplifications) to known features of the relevant metabolic pathways, but many of the mutations pointed to genes not previously associated with the relevant physiology. Thus, in addition to answering basic mechanistic questions about evolutionary mechanisms, our work suggests that experimental evolution can also shed light on the function and regulation of individual metabolic pathways.     

A System for Continuous Monitoring of Whole Shoot CO2 Exchange as an Adjunct to Growth Analysis Experiments in Controlled Environments

A multichannel system is described in which continuous CO₂ exchangemeasurements of whole shoots can be made on plants grown incontrolled environments such as growth cabinets, glasshouses,or plastic houses. The shoot enclosure is made from a coatedpolypropylene film which not only combines excellent light transmittancewith poor permeability to CO₂ but can also be tailored easilyto individual shoot systems of various sizes ensuring a rapidresponse time for CO₂ exchange measurements. Air speeds withinthe enclosure are regulated precisely; temperature and relativehumidity are also controlled to within narrow limits, duringdaylight hours and at night. Thus, the aerial environment ofenclosed shoots parallels closely that of non-enclosed plants. The system compliments a root respiration chamber designed earlier;used in conjunction with growth analysis data, the two systemsfacilitate quantitative determinations of the carbon economyof entire plants throughout all stages of growth.     

Metamaterial-Based Energy Harvesting for Detectivity Enhanced Infrared Detectors

Plasmonics - In this paper, we propose new detectivity enhanced infrared detectors in which metamaterial cells are used to harvest the IR energy. Analytical models are developed and numerically...     

DNA as a Flocculation Factor in Pseudomonas sp.

A component responsible for flocculation was extracted from Pseudomonas strain C-120 by treating the cells with 3 M guanidine hydrochloride. The guanidine hydrochloride-extracted cells were reflocculated, not only with the guanidine hydrochloride extract but with DNA prepared from various bacteria. The reconstituted flocs were deflocculated by deoxyribonuclease or guanidine hydrochloride which indicated that the reconstituted flocs closely resembled natural flocs. In reconstitution experiments using Escherichia coli DNA at different molecular weights, it was found that DNA with a molecular weight higher than about 6 × 10⁶ was required to flocculate the guanidine hydrochloride-extracted cells. Heat-denatured DNA did not flocculate the guanidine hydrochloride-extracted cells. DNA with a high molecular weight was detected in the guanidine hydrochloride extract. It was concluded that the component involved in flocculation of this organism was highly polymerized double stranded DNA.     

Chick Embryo Extract, Muscle Trophic Factor and Chick and Horse Sera as Environments for Chick Myogenic Cell Growth

Chick myogenic cells grew in a medium composed of Eagle's minimum essential medium (MEM), horse serum (HS), and one of the essential factors needed for myogenic cell growth (EFMG), that is, chick embryo extract (EE), chick serum (CS), or the muscle trophic factor (MTF). But they did not grow in the absence of the EFMG. In the absence of HS, they scarcely grew in a medium composed of MEM, and EE or MTF. They grew in a medium composed of MEM and CS; they grew much better in a medium composed of MEM, CS, and HS.
In the presence of one of the EFMG, the optimal HS concentration for growth varied depending on its lot. At higher HS concentrations, growth was suppressed. Further, it was suggested that an inhibitory substance(s) for myogenic cell growth was present in HS. The inhibitory effects can usually be minimized by diluting the serum with an artificial medium.     

The Effect of Temperature on Vegetative Growth in Climatic Races of Dactylis glomerata in Controlled Environments

The growth patterns in two natural populations of Dactylis glomeratafrom contrasting climatic regions, Norway and Portugal, werestudied at four constant temperatures (5, 10, 20, and 30°C) in a 16-h photoperiod. Marked changes in relative growth-rateat different temperatures were positively correlated with changesin both net assimilation rate and leaf-area ratio, whereas differencesbetween the populations in the relative growth-rate were theresult of differences in net assimilation rate, and were negativelycorrelated with differences in leaf-area ratio. The changesin leaf-area ratio at different temperatures were correlatedwith changes in leaf morphology and distribution of assimilateswithin the plant. The possible adaptive advantage of these vegetativegrowth patterns is discussed in relation to the survival ofthe plants in the original environments.