An Ecological Perspective on Root Physiology and Dynamics.

Many aspects of root physiology, growth and turnover can be better understood by using ecological principles, including optimization to minimize costs and maximize benefits and trade-offs associated with a particular growth strategy.  For example, root construction to produce surface area varies widely among species.  This may lead to trade-offs in mycorrhizal colonization or in the ability to proliferate in resource-rich patches.  Evidence for this trade-off can be found in citrus rootstocks, grape rootstocks and native tree species in the forest.  Roots also may be constructed to be well defended and live a long time, which may influence how these roots expend carbon for maintenance and defense.  This may influence resources expended to enhance specific nutrient and water absorption rates relative to that expended for defense against herbivores and pathogens. Such patterns of resource expenditure can be studied as a function of root age.  Short-lived roots may have high nutrient absorption rates initially, but decline rapidly with age.  Longer-lived roots may exhibit a lower, more stable pattern of nutrient absorption.  An ecological perspective is not only useful in understanding variation in root traits in wild species, but in many of our crop cultivars as well.