Co-ordination in Morphological Leaf Traits of Early Diverging Angiosperms Is Maintained Following Exposure to Experimental Palaeo-atmospheric Conditions of Sub-ambient O2 and Elevated CO2

In order to be successful in a given environment a plant should invest in a vein network and stomatal distribution that ensures balance between both water supply and demand. Vein density (D_v) and stomatal density (SD) have been shown to be strongly positively correlated in response to a range of environmental variables in more recently evolved plant species, but the extent of this relationship has not been confirmed in earlier diverging plant lineages. In order to examine the effect of a changing atmosphere on the relationship between D_v and SD, five early-diverging plant species representing two different reproductive plant grades were grown for 7 months in a palaeo-treatment comprising an O₂:CO₂ ratio that has occurred multiple times throughout plant evolutionary history. Results show a range of species-specific D_v and SD responses to the palaeo-treatment, however, we show that the strong relationship between D_v and SD under modern ambient atmospheric composition is maintained following exposure to the palaeo-treatment. This suggests strong inter-specific co-ordination between vein and stomatal traits for our study species even under relatively extreme environmental change. This co-ordination supports existing plant function proxies that use the distance between vein endings and stomata (D_m) to infer plant palaeo-physiology.

How well do you know your growth chambers? Testing for chamber effect using plant traits

BACKGROUND

Plant growth chambers provide a controlled environment to analyse the effects of environmental parameters (light, temperature, atmospheric gas composition etc.) on plant function. However, it has been shown that a 'chamber effect' may exist whereby results observed are not due to an experimental treatment but to inconspicuous differences in supposedly identical chambers. In this study, Vicia faba L. 'Aquadulce Claudia' (broad bean) plants were grown in eight walk-in chambers to establish if a chamber effect existed, and if so, what plant traits are best for detecting such an effect. A range of techniques were used to measure differences between chamber plants, including chlorophyll fluorescence measurements, gas exchange analysis, biomass, reproductive yield, anatomical traits and leaf stable carbon isotopes.

RESULTS AND DISCUSSION

Four of the eight chambers exhibited a chamber effect. In particular, we identified two types of chamber effect which we term 'resolvable' or 'unresolved'; a resolvable chamber effect is caused by malfunctioning components of a chamber and an unresolved chamber effect is caused by unknown factors that can only be mitigated by appropriate experimental design and sufficient replication. Not all measured plant traits were able to detect a chamber effect and no single trait was capable of detecting all chamber effects. Fresh weight and flower count detected a chamber effect in three chambers, stable carbon isotopes (δ(13)C) and net rate CO2 assimilation (An) identified a chamber effect in two chambers, stomatal conductance (gs) and total performance index detected an effect only in one chamber.

CONCLUSION

(1) Chamber effects can be adequately detected by fresh weight measurements and flower counts on Vicia faba plants. These methods were the most effective in terms of detection and most efficient in terms of time. (2) δ(13)C, gs and An measurements help distinguish between resolvable and unresolved chamber effects. (3) Unresolved chamber effects require experimental unit replication while resolvable chamber effects require investigation, repair and retesting in advance of initiating further experiments.

A retrospective immunohistochemical study of type II avian adenoviral infection in turkey, pheasant, and chicken tissues

A retrospective study of avian cases submitted to the Michigan Animal Health Diagnostic Laboratory between 1986 and 1992 produced four pheasant, five turkey, and five chicken cases in which splenic tissue was positive for type II adenoviral antigen using an agar gel immunodiffusion assay. Tissue sections from these cases were evaluated microscopically using both routine hematoxylin and eosin (H&E) staining and an immunohistochemical staining technique for type II adenoviral antigen. Tissues from all four pheasant cases and four of five turkey cases, but none of the five chicken cases, stained positively by histochemistry. Five additional chicken cases, obtained from the U.S. Department of Agriculture Eastern Laboratory of the Food Safety Inspection Service, had splenic lesions of undetermined etiology; these were also evaluated. One of the five cases had splenic inclusions on H&E staining and had strong positive histochemical staining. The immunohistochemical staining technique was sufficiently sensitive for use on diagnostic tissues that have been routinely fixed in formalin and processed for histopathology, and it detected all three recognized type II adenoviruses.