Diel (24 h) leaf growth patterns were differently affected by temperature variations and the circadian clock in several plant species. In the monocotyledon Zea mays, leaf elongation rate closely followed changes in temperature. In the dicotyledons Nicotiana tabacum, Ricinus communis, and Flaveria bidentis, the effect of temperature regimes was less obvious and leaf growth exhibited a clear circadian oscillation.These differences were related neither to primary metabolism nor to altered carbohydrate availability for growth. The effect of endogenous rhythms on leaf growth was analysed under continuous light in Arabidopsis thaliana, Ricinus communis, Zea mays, and Oryza sativa. No rythmic growth was observed under continuous light in the two monocotyledons, while growth rhythmicity persisted in the two dicotyledons. Based on model simulations it is concluded that diel leaf growth patterns in mono- and dicotyledons result from the additive effects of both circadian-clock-controlled processes and responses to environmental changes such as temperature and evaporative demand. Apparently very distinct diel leaf growth behaviour of monocotyledons and dicotyledons can thus be explained by the different degrees to which diel temperature variations affect leaf growth in the two groups of species which, in turn, depends on the extent of the leaf growth control by internal clocks.

This work evaluates the phenotypic response of the model grass (Brachypodium distachyon (L.) P. Beauv.) to nitrogen and phosphorus nutrition using a combination of imaging techniques and destructive harvest of shoots and roots. Reference line Bd21-3 was grown in pots using 11 phosphorus and 11 nitrogen concentrations to establish a dose-response curve. Shoot biovolume and biomass, root length and biomass, and tissue phosphorus and nitrogen concentrations increased with nutrient concentration. Shoot biovolume, estimated by imaging, was highly correlated with dry weight (R(2) > 0.92) and both biovolume and growth rate responded strongly to nutrient availability. Higher nutrient supply increased nodal root length more than other root types. Photochemical efficiency was strongly reduced by low phosphorus concentrations as early as 1 week after germination, suggesting that this measurement may be suitable for high throughput screening of phosphorus response. In contrast, nitrogen concentration had little effect on photochemical efficiency. Changes in biovolume over time were used to compare growth rates of four accessions in response to nitrogen and phosphorus supply. We demonstrate that a time series image-based approach coupled with mathematical modeling provides higher resolution of genotypic response to nutrient supply than traditional destructive techniques and shows promise for high throughput screening and determination of genomic regions associated with superior nutrient use efficiency.

In laboratory and greenhouse experiments with potted plants, shoots and roots are exposed to temperature regimes throughout a 24 h (diel) cycle that can differ strongly from the regime under which these plants have evolved. In the field, roots are often exposed to lower temperatures than shoots. When the root-zone temperature in Ricinus communis was decreased below a threshold value, leaf growth occurred preferentially at night and was strongly inhibited during the day. Overall, leaf expansion, shoot biomass growth, root elongation and ramification decreased rapidly, carbon fluxes from shoot to root were diminished and carbohydrate contents of both root and shoot increased. Further, transpiration rate was not affected, yet hydrostatic tensions in shoot xylem increased. When root temperature was increased again, xylem tension reduced, leaf growth recovered rapidly, carbon fluxes from shoot to root increased, and carbohydrate pools were depleted. We hypothesize that the decreased uptake of water in cool roots diminishes the growth potential of the entire plant -especially diurnally, when the growing leaf loses water via transpiration. As a consequence, leaf growth and metabolite concentrations can vary enormously, depending on root-zone temperature and its heterogeneity inside pots.

New approach to determine the inorganic carbon permeability across the chloroplast envelope, and to measure the role of aquaporin Pip1,2 on CO2 permeability.