Figure 1. Abiotic stress – phenotypic responses. (a) Drought-induced extreme leaf rolling in maize in the field (courtesy of Dr. RL Nielsen, Purdue University). (b) Storage of NaCl in modified trichomes (‘hairs’, termed epidermal bladder cells) induced by high salinity in the common ice plant.

Figure 2. A cellular view of salinity stress components. For an explanation of terms see the text (modified after Bohnert et al., 1995).

Figure 3. A unifying view – responses to abiotic stress. Acute stress is sensed by cells. Sensing follows a timeline, with very fast initial responses that initiate signalling events, which then establish the connection to altered gene transcription, changes in membrane trafficking of proteins, restructuring of metabolic pathway and altered hormonal and metabolic states. Recent studies have shown a completely new aspect of stress biology: plants express ‘antisense genes’ (siRNAs), which leads to the destruction of other transcripts whose presence would not be beneficial during stress (Borsani et al., 2005). Stresses also cause injuries, measured by independent signalling pathways, which lead to reactions for damage control and repair. Cell division and growth are reduced or continue, depending on the severity of a stress. Severe injury leads to the initiation of cell death-promoting programmes.