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UV and blue light control the expression of flavonoid biosynthesis genes in a range of higher plants. To investigate the signal transduction processes involved in the induction of chalcone synthase (CHS) gene expression by UV-B and UV-A/blue light, we examined the effects of specific agonists and inhibitors of known signaling components in mammalian systems in a photomixotrophic Arabidopsis cell suspension culture. CHS expression is induced specifically by these wavelengths in the cell culture, in a manner similar to that in mature Arabidopsis leaf tissue. Both the UV-B and UV-A/blue phototransduction processes involve calcium, although the elevation of cytosolic calcium is insufficient on its own to stimulate CHS expression. The UV-A/blue light induction of CHS expression does not appear to involve calmodulin, whereas the UV-B response does; this difference indicates that the signal transduction pathways are, at least in part, distinct. We provide evidence that both pathways involve reversible protein phosphorylation and require protein synthesis. The UV-B and UV-A/blue light signaling pathways are therefore different from the phytochrome signal transduction pathway regulating CHS expression in other species.

Empirical flow laws have been determined for Simpson quartzite samples deformed to mechanical steady state in the α‐quartz stability field using Griggs‐Blacic solid‐medium deformation apparatus. Experiments were conducted on samples both as received (“dry”) and with water added via the dehydration of a talc confining medium (“wet”). Best fits of the power law type yield a stress exponent of 2.72±0.19, an activation enthalpy of 134±32 kJ mol−1, and a preexponential constant of 1.16 [+1.15, −0.58] × 10−7 MPa−2.72 s−1 for the dry quartzite law; and are 2.61±0.15, 145±17 kJ mol−1, and 5.05 [±5.00] × 10−6 MPa−2.61 s−1 for the wet quartzite. The enhanced hydrolytic weakening of the wet experiments appears to affect the flow laws mostly in the preexponential constants, possibly as a defect concentration term that is higher in the wet than in the dry law. Over the range of experimental conditions (750°–900°C, 10−7 to 10−4 s−1, and 1.0–1.25 GPa confining pressure), dry specimens are 1.5–2.5 times stronger than wet samples deformed at the same conditions. The microstructures produced are analogous to those observed in many natural quartz tectonites. Recrystallization is well developed in the wet but not the dry specimens. At flow stresses below 500 MPa, microstructures indicative of recovery are well developed. A comparison of our creep activation enthalpies with those determined from diffusion experiments are consistent with deformation of wet Simpson quartzite that is limited by oxygen self‐diffusion. Inconsistencies between the present study and previous studies are probably the result of differences in sample material, sample treatment, and sample assemblies (chemical environment).