Freeze-marking rodents with a pressurized refrigerant

The effectiveness of a pressurized refrigerant, dichlorodifluoromethane (CCl₂F₂) for the freeze-marking of rodents was investigated. Application for 4 sec or longer was equally effective in marking both shaven and unshaven laboratory mice (Mus musculus). Two species of wild iats, Rattus norvegicus and R. rattus, were also successfully marked by applying the refrigerant to unshaven animals for periods of 5–10 sec. Attempts at marking coypus (Myocastor coypus) were less successful. General anaesthesia was found to be unnecessary in the case of unshaven rats and mice since the refrigerant itself produced a local anaesthetic effect. The use of the refrigerant in conjunction with stencils to obtain more specific markings is discussed.     

Root-Shoot Interactions in Peach: The Function of the Root

Peach seedlings were grown in aerated nutrient solution in small(15 cm³) or large (500 cm³) containers. Subsequently, some plantswere removed from the small containers to the large, or werestressed by root pruning. Half the plants received a foliarspray of synthetic cytokinin 6-benzylaminopurine (BAP) every4 days. Analysis of all the results enabled correlations between functionand growth measurements to be made. Irrespective of the treatmentthe total water and the total nutrient uptake by the roots wasdirectly related to the total dry weight increment. This suggeststhat for both water and nutrient uptake a functional equilibriumexisted between the root and the shoot. Where BAP treatmentincreased the top: root ratio there was a corresponding increasein the rate of water uptake per unit length of root. The relationship between root number and leaf number and thecomplementary action of BAP suggests that the root tip and itsproduction of cytokinins exerts considerable control over topgrowth.