Rice germination and seedling growth in the absence of oxygen.
BACKGROUND
Higher plants are aerobic organisms which suffer from the oxygen deficiency imposed by partial or total submergence. However, some plant species have developed strategies to avoid or withstand severe oxygen shortage and, in some cases, the complete absence of oxygen (tissue anoxia) for considerable periods of time.


METHODS
Rice (Oryza sativa) is one of the few plant species that can tolerate prolonged soil flooding or complete submergence thanks to an array of adaptive mechanisms. These include an ability to elongate submerged shoot organs at faster than normal rates and to develop aerenchyma, allowing the efficient internal transport of oxygen from the re-emerged elongated shoot to submerged parts. However, rice seeds are able to germinate anaerobically by means of coleoptile elongation. This cannot be explained in terms of oxygen transport through an emerged shoot. This review provides an overview of anoxic rice germination that is mediated through coleoptile rather than root emergence.


CONCLUSIONS
Although there is still much to learn about the biochemical and molecular basis of anaerobic rice germination, the ability of rice to maintain an active fermentative metabolism (i.e. by fuelling the glycolytic pathway with readily fermentable carbohydrates) is certainly crucial. The results obtained through microarray-based transcript profiling confirm most of the previous evidence based on single-gene studies and biochemical analysis, and highlight new aspects of the molecular response of the rice coleoptile to anoxia.
Magneschi
Leonardo
L
Plant & Crop Physiology Lab, Scuola Superiore Sant'Anna, Piazza Martiri della Libertà 33, 56127 Pisa, Italy.
Perata
Pierdomenico
P
D015687:Cell Hypoxia; D018525:Germination / Q000502:physiology*; D053858:Metabolic Networks and Pathways; D012275:Oryza / Q000166:cytology / Q000201:enzymology / Q000502:physiology*; D010100:Oxygen / Q000378:metabolism*; D036226:Seedlings / Q000166:cytology / Q000201:enzymology / Q000254:growth & development* / Q000378:metabolism
D010100:Oxygen