Can an increased copper requirement in copper-tolerant Mimulus guttatus explain the cost of tolerance? II. Reproductive phase

Circumstantial evidence suggests that plants that have evolved metal tolerance are at a disadvantage on normal soil, i.e. there is a cost of tolerance. One hypothesis for the cause of this cost is that individuals have a greater requirement for copper, and so suffer micronutrient deficiency on normal soils, as a result of a reduced uptake, distribution and/or utilization of copper. We provided highly and less copper-tolerant plants of Mimulus guttatus Fischer ex DC. (the common monkey flower) with sub-optimal copper, and demonstrated the importance of copper as an essential micronutrient during the reproductive phase, both in the production of viable pollen and in seed set. We also looked at the effect of sub-optimal copper supply on the growth of the microgametophyte, and the efficiency with which seed was set. No evidence was found that highly tolerant plants have an increased copper requirement during the reproductive phase. This is in agreement with earlier work on Mimulus guttatus , which investigated the copper requirement of highly tolerant plants during vegetative growth and found that any differences in copper requirement were small. The 'metal requirement hypothesis' is, therefore, not the sole explanation for the cost of copper tolerance in M. guttatus .     

Environmental constraints on the efficiency of selection for malting quality in barley

A range of screening tests has been applied to samples of barley from breeders' trials to evaluate the usefulness of rapid tests. The prediction of the malting potential of genotypes over seasons was best achieved by the use of hot water extract measurements. Environmental effects can result in a poor relationship between hot water extract and grain characters such as β-glucan content and thousand corn weight. Hot water extract varied considerably over sites, but results relative to a control cultivar were consistent provided that trials in which material malted poorly were eliminated from the comparisons.     

Trial Implantation of Heart Rate Data Loggers in Pinnipeds

ABSTRACT Pinnipeds are major consumers in marine ecosystems, and understanding their energy budgets is essential to determining their role in food webs, particularly where there is competition with fisheries. Food consumption and energy expenditure have been evaluated in pinnipeds using different methods, but the use of heart rate to estimate energy expenditure is potentially a very powerful tool suited to the life history of these animals. We tested a procedure for the subcutaneous implantation of heart rate data loggers to determine whether heart rate could be recorded for ≥1 year in free-ranging pinnipeds, as it has been in birds. We implanted 3 captive California sea lions (Zalophus californianus) and 3 captive northern elephant seals (Mirounga angustirostris) with heart rate data loggers and monitored their recovery and behavior in a controlled environment. In both species, the implantation site allowed for excellent detection of the electrocardiogram, and we observed heart rate signatures characteristic of behaviors such as resting and diving. Although all 3 sea lions recovered well from the implantation surgery, all 3 elephant seals showed a substantial inflammatory response for unknown reasons, and we removed the implanted data loggers. Subcutaneous implantation of data loggers is a powerful technique to study physiology, energetics, and behavior in California sea lions, but more work is required to realize the potential of this technique in northern elephant seals.     

The green-veined white (Pieris napi L.), its Pierine relatives, and the systematics dilemmas of divergent character sets (Lepidoptera, Pieridae)

The butterfly Pieris napi (L.) and relatives exemplify recently evolving taxa, exhibiting variation that makes their evolutionary dynamics interesting, but their systematics difficult. Wing-pattern characters commonly used to distinguish these Holarctic insects display both genetic polymorphism and environmentally-cued polyphenism. Often, these causes of variation are confounded, impairing the characters' phylogenetic usefulness. DNA sequences of four mitochondrial genes offer an independent view of pierine phylogeny. Sampling diverse relatives within family Pieridae assists resolution of the P. napi complex, suggests previous underestimation of clade diversity in subfamily Pierinae, and shows that other genera near Pieris also display confusions of wing-pattern-based phylogenetic inference. The European P. napi is sister to all North American taxa, and is well diverged from them all in sequences. The North American taxa comprise a northern subclade including Pieris oleracea , and questionably distinct Pieris ' angelika ', and a southern subclade including distinct Pieris virginiensis , Pieris marginalis , and Pieris macdunnoughii , and other regional entities yet to be clarified. Weak bootstrap support for some nodes in this group arises from a closeness of sequence identity rather than character conflict; more sequence data and denser geographical sampling may resolve these nodes more clearly. Evidence of reproductive isolation, from other experimental hybridization studies, agrees with the DNA results where these conflict with other divergent character sets. The system offers much promise for a deeper understanding of character evolution in relation to phyletic differentiation.  © 2006 The Linnean Society of London, Biological Journal of the Linnean Society , 2006, 88 , 413–435.     

Embryoid Formation in Pollen Grains of Nicotiana tabacum

Anthers of Nicotiana tabacum (n = 24) were cultured on nutrientagar and examined at intervals for pollen embryoids. Embryoidswere formed in anthers of varying developmental stage, the youngestof which coincided with the liberation of free microspores fromtetrads, and the oldest with the formation of bicellular grains.This period in the development of the anther occupied 4–5days. Older anthers within this range were more successful thanyounger anthers. The first mitosis of the pollen was typicallyasymmetric and resulted in the formation of unequal generativeand vegetative cells. Some of the grains then went into a lagphase for at least 5–6 days, after which the mitotic conditionwas restored. Embryoids were formed by repeated division ofthe vegetative cell. If the generative cell divided, it didso only once or twice. Occasionally the first mitosis was symmetricand gave rise to equal cells, and in these instances both cellsprobably participated in embryoid formation. The youngest anthersexamined were probably less successful because fewer grainssurvived to enter mitosis. The number of embryoids produced varied considerably from oneanther to another both within the same bud and between differentbuds: values ranging from less than 400 to 10 000 per antherwere encountered. Most of these degenerated after the firstfew divisions, partly because they burst prematurely from thepollen grain wall. Embryoids which continued to develop formedplantlets and/or callus. The largest number of plantlets obtainedfrom one anther was 32. Haploid plantlets were also regeneratedfrom callus by transferring it to a low-sugar medium withoutauxin. The behaviour of grains not forming embryoids was also noted.     

THE APPLICATION OF THE DYNAMIC TRIANGLE OLFACTOMETER TO THE EVALUATION OF ORAL ODOR

The Dynamic Triangle Olfactometer, an instrument which measuresodor thresholds by a system functionally based on the principlesof steady state dynamic flow, dilution and forced choice triangledesign, was evaluated and found to be most acceptable for itsutility in appraising the efficacy of breath freshening formulationsin relieving or controlling extrinsic (onion) oral malodor. Initially, the olfactory acuity of a panel of novice judgeswas ascertained by the development of thresholds for hydrogensulfide and methyl mercaptan, both compounds related to oralmalodor, especially extrinsic as induced by an aqueous suspensionof onion oil used in this study. The threshold for onion oilwas also established. Several breath freshening formulationswere demonstrated to be effective in controlling extrinsic oralmalodor under the conditions of this study. The operational parameters of the DTO system were uncomplicatedand the data so obtained was reproducible. The panel of judgesapproximated the distribution of olfactory sensitivity of anormal population; therefore, the performance of the formulationsas measured in this system should be, and is, reasonably predictiveto a consumer population.