Systems for inter-organ communication

In order to successfully survive, all living organisms require a system to respond to the continuously changing environment, and to regulate the various developmental processes in cells and organs at different locations in the body. The following discussion highlights the communication systems in plants with special emphasis on reproductive aspects.

In animals, two major systems are involved in inter-organ communication, i.e. the nervous system and the hormone system. In addition, the immune system uses different classes of chemical messengers (e.g. interleukins, interferons, nitric oxide) to coordinate the defence response (Norman & Litwack, 1987; Roitt, Brostaff & Male, 1993). Although the metabolism of individual plant and animal cells may show many similarities, there is no a priori reason why the mechanisms, involved in the responses to environmental cues and in communication between different organs should in any way be the same. However, systems showing some similarities to the animal nervous system have been found in plants. For instance, mechanisms have evolved to respond within seconds to mechanical perturbation in Drosera (sundew) and Mimosa pudica. The movements of the leaves of Mimosa pudica are regulated by motor organs (pulvini) and are the result of turgor variations in the cortical (motor) cells of these organs. It has been shown that ionic migration, in particular of K+ and C1−, appears in the pulvinus, concomitant with the turgor changes (Satter & Galston, 1981; Fleurat-Lessard et al., 1988).