Mesophyll resistance to CO(2) uptake was calculated from gas exchange data on intact leaves of 12 species of woody plants. Plants studied were native to habitats ranging from streamsides to deserts. Gas exchange measurements were made at light saturation and constant temperature to eliminate possible effects of light and temperature on estimates of mesophyll resistance. Cuticular transpiration ...

Willow (Salix babylonica L.) is representative of a large group of plants that have extensive plasmodesmatal connections between minor vein phloem and adjoining cells. Because plasmodesmata provide a diffusion pathway for small molecules, it is unclear how sucrose could be loaded from the mesophyll into the phloem against a concentration gradient. In the studies reported here, the minor vein ph...

Container-grown black spruce (Picea mariana (Mill.) B.S.P.) seedlings were planted in trays containing a sand and peat mixture, and placed in a climate-controlled greenhouse. One group of seedlings was kept well-watered, and another group was subjected to three cycles of drought. Gas exchange analysis showed that mesophyll photosynthetic function was largely unimpaired by drought. In contrast, ...

A technique is described for the separation of mesophyll and bundle sheath cells from Digitaria sanguinalis leaves and evidence for separation is given with light and scanning electron micrographs. Gentle grinding of fully differentiated leaves in a mortar releases mesophyll cells which are isolated on nylon nets by filtration. More extensive grinding of the remaining tissue yields bundle sheat...

Stomata control gaseous fluxes between the internal leaf air spaces and the external atmosphere. Guard cells determine stomatal aperture and must operate to ensure an appropriate balance between CO2 uptake for photosynthesis (A) and water loss, and ultimately plant water use efficiency (WUE). A strong correlation between A and stomatal conductance (gs ) is well documented and often observed, bu...

In the C4 plant maize, three photosynthetic cell types differentiate: C4 bundle sheath, C4 mesophyll, and C3 mesophyll cells. C3 mesophyll cells represent the ground state, whereas C4 bundle sheath and C4 mesophyll cells are specialized cells that differentiate in response to light-induced positional signals. The Golden2 (G2) gene regulates plastid biogenesis in all photosynthetic cells during ...

C4 photosynthesis depends on the strict compartmentalization of CO2 assimilatory enzymes. cis-regulatory mechanisms are described that ensure mesophyll-specific expression of the gene encoding the C4 isoform of phosphoenolpyruvate carboxylase (ppcA1) of the C4 dicot Flaveria trinervia. To elucidate and understand the anatomy of the C4 ppcA1 promoter, detailed promoter/reporter gene studies were...

Water use efficiency (WUE) is considered as a determinant of yield under stress and a component of crop drought resistance. Stomatal behavior regulates both transpiration rate and net assimilation and has been suggested to be crucial for improving crop WUE. In this work, a dynamic model was used to examine the impact of dynamic properties of stomata on WUE. The model includes sub-models of stom...

The intercellular distribution of the enzymes and metabolites of assimilatory sulfate reduction and glutathione synthesis was analyzed in maize (Zea mays L. cv LG 9) leaves. Mesophyll cells and strands of bundle-sheath cells from second leaves of 11-d-old maize seedlings were obtained by two different mechanical-isolation methods. Cross-contamination of cell preparations was determined using ri...

To determine the driving forces for symplastic sugar flux between mesophyll and phloem, gradients of sugar concentrations and osmotic pressure were studied in leaf tissues of two Scrophulariaceae species, Alonsoa meridionalis and Asarina barclaiana. A. meridionalis has a typical symplastic configuration of minor-vein phloem, i.e. intermediary companion cells with highly developed plasmodesmal c...