Coordination Between Shoots and Roots

Publisher Summary This chapter explores the differences between the shoot and root environment and the relationship that exists between shoots and roots. Communication among partners is paramount for such a relationship to flourish or even survive. The success of plants on land attests to the effectiveness of this shoot/root communication over long distances, and the evolutionary trend is for greater differentiation between shoots and roots. Successful coordination among dissimilar partners is complicated, and many aspects about shoot/root communications remain unresolved. Shoots and roots of higher plants are distinct in form and function. They coordinate their activities achieving a functional equilibrium between the two organs through several mechanisms. Translocation of carbohydrates from shoots to roots and water and nutrients from roots to shoots are balanced according to the resource needs of the exporting organ. Phytohormones such as cytokinins and auxins and amino acids such as asparagine, glutamine, and glutamate act as messengers between the two organs and regulate shoot versus root growth. Atmospheric levels of CO 2 are rising at an unprecedented rate, and shoots are more sensitive than roots to such changes. As a result, the terrestrial flora may experience major shifts.