From Cell Division to Organ Shape: Nitric Oxide Is Involved in Auxin-Mediated Root Development - Communication in Plants: Neuronal Aspects of Plant Life - page 133

in cucumber explants since the effect of both auxins and NO is abolished
when one of them is compromised (Fig. 9.3).
9.4
Conclusions and Future Perspectives
We are clearly taking the first steps in order to describe at what different
levels NO modulates root morphology and physiology. Nevertheless, the
major challenge will be the integration of the myriad of signals involved
in root development and the linkage between them and the different enzy-
matic and nonenzymatic NO sources in roots.
Considerable effort and imagination will be necessary to design innova-
tive approaches and experimental models which should include different
factors affecting the signals associated with root growth. The availability
of water, oxygen and nutrients, the interaction with soil microorganisms
(pathogens and nonpathogens), the production and modification of plant
growth-promoting compounds by those organisms together with the ge-
neticbackgroundofeachplantspeciesshouldbeconsideredandintegrated
in the near future. The application of genetic tools and the analysis of root
growth behavior under different soil conditions will surely contribute to
deciphering the participation of root systems in plant productivity. In turn,
NO which has been postulated as a key player in many of the known auxin-
mediated processes associated with root development, should be consid-
ered as a mammalian-like neurotransmitter when describing its behavior
in future discussions.
The basic knowledge discussed in this review will clearly have a tremen-
dous impact owing to its potential application for improving programs of
rooting that are actually being used in nurseries. Undoubtedly, NO actions
should be taken into account when studying the specific requirements of
each plant species that determines its root growth pattern.
Acknowledgements. This work was supported by ANPCyT, CONICET, Fun-
dación Antorchas and UNMdP, Argentina.
References
Baluška F, Šamaj J, Menzel D (2003) Polar transport of auxin: carrier-mediated flux
across the plasma membrane or neurotransmitter-like secretion? Trends Cell Biol 13:
282-285
Baluška F, Mancuso S, Volkmann D, Barlow P (2004) Root apices as plant command centres:
the unique 'brain-like' status of the root apex transition zone. Biologia 59:7-19