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The nature of the design process and how to develop this skill in novice designers has been of considerable interest to technology educators. The relationship between workplace and school-based design is one area in which a need for further research has been identified by Hill and Anning (2001, "International Journal of Technology and Design Education" 11, 111-136). The research project described in this article had two aims. The first was to compare the workplace practice of six experienced designers with their practice when working on a technological assessment task as part of a pre-service teacher education programme. The second aim was to investigate their experience on teaching practicum in developing design skills with secondary school students. Findings from the research are described and the paper concludes with a discussion of the implications for teaching technology education.

The potential for thermal acclimation of photosynthetic electron transport by guard cell chloroplasts (GC ch) was assessed in epidermal peels taken from the abaxial side of Saxifraga cernua leaves grown at 20°C and 10°C. Chlorophyll a fluorescence induction kinetics measured in pairs of guard cell in individual stomata from tissue grown at 10°C demonstrated a rise in the fluorescence to a maximum and a larger amplitude in variable fluorescence when measured at temperatures below 18°C than was seen in GC ch from tissue grown at 20°C. The rates of fluorescence quenching in 10°C- grown tissue were also faster than in 20°C-grown tissue when measured at temperatures below 18°C State 1-State 2 transitions by GC ch were measured at selected temperatures between 5 and 25°C as changes in the magnitude of the fluorescence emission maxima at 685, 695 arid 730 nm (F685, F695 and F730) measured at 77K At measuring temperatures of 5 and 10°C, GC ch in tissue grown at 10°C showed a greater transition to State 2 (a larger F730/F695 ratio) than did GC ch in tissue grown at 20°C. At measuring temperatures of 20 and 25°C, there was no difference in either the kinetics or the magnitude of the State 1 to State 2 transition in the two tissues. The ultrastructure of GC ch from tissues grown at 10 and 20°C was also examined using transmission electron microscopy. Less than half (48%) of the grana from the higher temperature grown tissue had more than nine thylakoids/grana Grana in GC ch which had developed at 10°C showed a dramatic reduction in stacking, such that 85% of the grana contained no more than two thylakoids. The reduction in grana stacking was also accompanied by a decrease in the degree of appression of thylakoid membranes. The results demonstrate a capacity for thermal acclimation of GC ch function to low temperature. This acclimation is associated with alterations in the chloroplast ultrastructure. [ABSTRACT FROM AUTHOR]

This article mentions people that the author would like to thank for the skillful leadership and drive in the launching of the journal.

Chlorophyll a fluorescence transients from mesophyll and single guard cell pairs of Vicia faba were measured by microspectrofluorometry. In both chloroplast types, fluorescence induction (O to P) was similar under actinic blue and green light. In slow transients from mesophyll cell chloroplasts, blue and green light induced identical, typical rapid quenching from P to S, and the M peak. In contrast, the P to S transient from guard cell (GC) chloroplasts irradiated with blue light showed a much slower quenching rate, and the P to T transition showed no M peak. Actinic green light induced mesophyll-like transients in GC chloroplasts, including rapid quenching from P to S and the M peak. Detection of these transients in single pairs of GC and isolated protoplasts ruled out mesophyll contamination as a signal source. Green light induced a rapid quenching and the M peak in GC chloroplasts from several species. The effect of CO(2) concentration on the fluorescence transients was investigated in the presence of HCO(3) (-) at pH 6.8 and 10.0. In transients induced by green light in both chloroplast types, a pH increase concomitant with a reduction in CO(2) concentration caused an increase in the initial rate of quenching and the elimination of the M peak. Actinic blue light induced mesophyll-like transients from GC chloroplasts in the presence of 10 micromolar KCN, a concentration at which the blue light-induced stomatal opening is inhibited. Addition of 100 to 200 micromolar phosphate also caused large increases in fluorescence quenching rates and a M peak. These results indicate that blue light modulates photosynthetic activity in GC chloroplasts. This blue light effect is not observed in the absence of transduction events connected with the blue light response and in the presence of high phosphate concentrations.

Fluorescence emission spectral peaks at 685, 695 and 730 nanometers (F685, F695, and F730) were recorded 77 K from diluted leaf tissue and epidermal powders prepared from Saxifraga cernua. The time course for state 1 to state 2 transitions was monitored as changes in the ratios of the three emission peaks. During illumination with light 2 (580 nm) the F730/F695 and F730/F685 ratios increased within minutes to establish a condition characteristic of state 2. A major difference between the two chloroplast types was the more rapid establishment of state 2 by mesophyll chloroplasts. An increase in light 2 intensity caused an increase in the magnitude of the F730/F695 ratio for both chloroplast types and, for guard cell chloroplasts, a decrease in the time required to establish the new ratio. The role of reversible phosphorylation of the light-harvesting chlorophyll a/b protein complex in regulating state transitions for both mesophyll and guard cell chloroplasts was assessed using DCMU and sodium fluoride, a specific phosphatase inhibitor. DCMU-treated mesophyll and epidermal tissues failed to show a state 1-state 2 transition. NaF-treated tissues attained state 2 but lacked the ability to revert back to state 1.

Abscisic acid (AbA) treatments of concentrations of up to 135 micromolar did not inhibit photosynthesis in enzymatically isolated leaf mesophyll cells of Phaseolus vulgaris, Nicotiana tabacum, and Lycopersicum esculentum over periods of up to 5 hours. Thin slices of leaves preincubated in hypertonic solutions identical to those used to isolate cells were shown to synthesize AbA rapidly, although accumulation of AbA in the cells was low due to extensive release of the newly synthesized AbA into the medium. The levels of endogenously made AbA in leaf cells of Phaseolus vulgaris rose from a low of 0.27 micromolar to a high of 6.74 micromolar during 2 hours preincubation. Exogenously applied AbA can be taken up by the cells as was demonstrated using (14)[C]AbA. Thus, AbA applied at concentrations 19 times higher than endogenous levels does not change the rate of photosynthesis.

Thermal acclimation by Saxifraga cernua to low temperatures results in a change in the optimum temperature for gross photosynthetic activity and may directly involve the photosynthetic apparatus. In order to test this hypothesis photosynthetic electron transport activity of S. cernua thylakoids acclimated to growth temperatures of 20 degrees C and 10 degrees C was measured in vitro. Both populations exhibited optimum temperatures for whole chain and PSII electron transport activity at temperatures close to those at which the plants were grown. Chlorophyll a fluorescence transients from 10 degrees C-acclimated leaves showed higher rates in the rise and subsequent quenching of variable fluorescence at low measuring temperatures; 20 degrees C-acclimated leaves showed higher rates of fluorescence rise at higher measuring temperatures. At these higher temperatures, fluorescence quenching rates were similar in both populations. The kinetics of State 1-State 2 transitions in 20 degrees C- and 10 degrees C-acclimated leaf discs were measured as changes in the magnitude of the fluorescence emission maxima measured at 77K. Leaves acclimated at 10 degrees C showed a larger F730/F695 ratio at low temperatures, while at higher temperatures, 20 degrees C-acclimated leaves showed a higher F730/F695 ratio after the establishment of State 2. High incubation temperatures also resulted in a decrease in the F695/F685 ratio for 10 degrees C-acclimated leaves, suggesting a reduction in the excitation transfer from the light-harvesting complex of photosystem II to photosystem II reaction centers. The relative amounts of chlorophyll-protein complexes and thylakoid polypeptides separated electro-phoretically were similar for both 20 degrees C- and 10 degrees C-acclimated leaves. Thus, photosynthetic acclimation to low temperatures by S. cernua is correlated with an increase in photosynthetic electron transport activity but does not appear to be accompanied by major structural changes or different relative amounts in thylakoid protein composition.

The chlorophyll fluorescence induction curves from mesophyll and guard cell chloroplasts of Saxifraga cernua, including both the fast (O to P, the transients involved in the rise in variable fluorescence) and slow (P to steady state fluorescence due to quenching) components, were characterized over a range of excitation intensities using microspectrophotometry (with epi-lumination) equipped with apertures designed to eliminate cross contamination of the fluorescence signal between the two chloroplast types. At low excitation intensities, the fast fluorescence kinetics from guard cell plastids showed an extended I to D phase and a more rapid appearance of P while minimal quenching from P to steady state fluorescence was observed compared to the transients from mesophyll chloroplasts suggesting a lower activity of photochemical (electron movement via carriers between donor and acceptor sites) and nonphotochemical (such as membrane conformational changes) events which regulate the fluorescence induction curve kinetics. As the excitation intensity was increased, the quenching rates of guard cells were faster at initiating conditions for photophosphorylation and the fast and slow fluorescence kinetics from guard cells resembled those of the mesophyll cells.Guard cell chloroplasts of S. cernua from intact epidermal peels showed a low temperature (77 K) fluorescence emission spectrum having three major peaks (at 685, 695, and 730 nanometers when excited at 440 nanometers) which were qualitatively similar to those in the spectrum obtained from mesophyll tissue.These data suggest that S. cernua guard cell chloroplast photosystems I and II contribute to light-dependent stomatal activity only at high light intensities.