Rice in deep water: "How to take heed against a sea of troubles"

 Plants are aerobic organisms for which oxygen shortage poses a severe problem. Waterlogging and flooding are the main causes of anaerobiosis and can lead to damage or even death of the plant. Rice is well adapted to semi-aquatic conditions. It is the only cereal that can be grown in flooded areas such as the great river deltas of Asia. In rice, two major strategies have evolved to cope with conditions of flooding. One is to escape submergence and thereby avoid anaerobiosis as much as possible. This is achieved through elongation growth and through extensive aeration of submerged plant parts by way of internal and external air spaces. The second adaptation is a metabolic one which includes the efficient use of carbohydrate resources and maintenance of energy charge when the cells do become anaerobic. The mainly ethanolic fermentation pathway found in anaerobic rice avoids acidification of the cytoplasm and thereby contributes to the maintenance of cell integrity. Genetic analysis indicates that the submergence tolerance trait, which is based on metabolic changes, is encoded by only one or a few as yet unidentified gene(s). Identifying these genes is a major goal in anaerobic stress research.     

Weaning in the guinea pig (<Emphasis Type="Italic">Cavia aperea</Emphasis> f. <Emphasis Type="Italic">porcellus</Emphasis>): Who decides and by what measure?

Offspring should be selected to influence maternal effort to maximize their own fitness, whereas mothers are selected to limit investment in present progeny. In mammals, this leads to a conflict over the amount of milk provided and the timing of weaning. The intensity and time course of such conflict has so far mostly been investigated experimentally in altricial rodents. However, it is expected that offspring options for conflict will depend on developmental state. We therefore investigated in the highly precocial domestic guinea pig (Cavia aperea f. porcellus) who decides over nursing performance and weaning and how pup state influences these decisions. Specifically, we tested whether a threshold mass of pups predicts weaning time. By exchanging older litters against neonates and vice versa, we produced a situation in which females differed in lactational stage from the cross-fostered pups. Our results indicate that females decide about the timing of weaning, as cross-fostered younger pups were weaned at a much younger age than controls and older pups benefited from continuing lactation of foster mothers. Growth rates did not differ in the treatment groups, and different weaning ages resulted in differing weaning mass refuting the hypothesis that weaning is based on a threshold mass of offspring. This constitutes clear evidence that in a precocial rodent, the guinea pig, decisions about maternal care are primarily determined by maternal state and little influenced by pup state despite the extreme precociality of offspring. We suggest that precocial pups show little resistance to early weaning when food is abundant, as they reach sufficient nutritional independence by the middle of lactation to enable independent survival.