Stomatal conductances of Vicia faba leaves were recorded over a day. Coordinately, (a) guard cells dissected from leaflets were assayed, providing total sucrose content, and (b) guard cells dissected from rinsed epidermes were also assayed, providing symplastic sucrose content. Compared with that of pre-dawn samples, apoplastic sucrose content increased 4.8-5.2 × (2 experiments), reaching 1,130-1,300 fmol.guard-cell-pair -~ at midday, when conductance was highest (ca. 0.13 mol.m-2.s-~); symplastic sucrose content increased 2.5-3.5 ×, reaching 350-390 fmol" guard-cell-pair -1. Thus, there is a correlation between transpiration and guard-cell sucrose content, particularly that portion localized to the apoplast. Moreover, apoplastic sucrose is apparently a source of guard-cell nutrition and, possibly, osmoticum.

, in the estimated aqueous volume of the guard-cell wall. The conclusion is that mannitol, a xenobiotic with structural similarity to sucrose, can move throughout the apoplast of a transpiring leaflet and accumulate in an osmotically significant concentration in the guard-cell wall. These data therefore provide support for a new role for sucrose as a signal metabolite that integrates essential functions of the whole leaf. In addition, the results raise questions about the physiological or experimental accumulation of other guard-cell-targeted apoplastic solutes such as plant growth regulators, particularly abscisic acid, and ions.

A quantitative evaluation was made of a food puzzle designed to be a behavioral enrichment device for captive chimpanzees. Subjects were two social groups of chimpanzees housed in semifree-ranging conditions at the University of Texas Science Park in Bastrop. Subjects used the device for a mean of 91.6 minutes after it was filled with peanuts. Group levels of agonistic interactions, displays, coprophagy, regurgitation, excessive grooming, and consumption of wood were not significantly altered by the use of the peanut box. However, the data indicate that some of these categories of behavior were significantly increased or decreased in individual animals. Although the food puzzle box appears to be a promising behavioral enrichment tool, the necessity of recognizing individual differences in response to environmental manipulations must be emphasized.

No abstract

Apoplastic phloem loaders have an apoplastic step in the movement of the translocated sugar, prototypically sucrose, from the mesophyll to the companion cell-sieve tube element complex. In these plants, leaf apoplastic sucrose becomes concentrated in the guard cell wall to nominally 150 mM by transpiration during the photoperiod. This concentration of external sucrose is sufficient to diminish stomatal aperture size in an isolated system and to regulate expression of certain genes. In contrast to apoplastic phloem loaders and at the other extreme, strict symplastic phloem loaders lack an apoplastic step in phloem loading and mostly transport raffinose family oligosaccharides (RFOs), which are at low concentrations in the leaf apoplast. Here, the effects of the phloem-loading mechanism and associated phenomena on the immediate environment of guard cells are reported. As a first step, carbohydrate analyses of phloem exudates confirmed basil (Ocimum basilicum L. cv. Minimum) as a symplastic phloem-loading species. Then, aspects of stomatal physiology of basil were characterized to establish this plant as a symplastic phloem-loading model species for guard cell research. [(14)C]Mannitol fed via the cut petiole accumulated around guard cells, indicating a continuous leaf apoplast. The (RFO+sucrose+hexoses) concentrations in the leaf apoplast were low, <0.3 mM. Neither RFOs (<10 mM), sucrose, nor hexoses (all, P >0.2) were detectable in the guard cell wall. Thus, differences in phloem-loading mechanisms predict differences in the in planta regulatory environment of guard cells.