Hyperpolarization-activated K channels (KH channels) in the plasmalemma of guard cells operate at apoplastic pH range of 5 to over 7. Using patch clamp in a whole-cell mode, we characterized the effect of varying the external pH between 4.4-8.1 on the activity of the KH channels in isolated guard cell protoplasts from Vicia faba leaves. Acidification from… (More)
Previous studies reveal that the pH of the apoplastic solution in the guard cell walls may vary between 7.2 and 5.1 in closed and open stomata, respectively. During these aperture and pH changes, massive K+ fluxes cross the cellular plasma membrane driving the osmotic turgor and volume changes of guard cells. Therefore, we examined the effect of… (More)
The mechanism by which the mature leaf of certain plants reorients its lamina to face the sun throughout the day was studied in Lavatera cretica L. The photoreceptor for this response differs fundamentally from the one involved in the phototropic growth response, by sensing light as a vector, rather than as a difference in luminous flux. The photoreceptor… (More)
Photosensitive caged compounds have enhanced our ability to address the complexity of biological systems by generating effectors with remarkable spatial/temporal resolutions. The caging effect is typically removed by photolysis with ultraviolet light to liberate the bioactive species. Although this technique has been successfully applied to many biological… (More)
On a clear day, leaf laminas of Lavatera cretica tracked the solar position throughout the day. The laminar azimuth did not diverge from the solar azimuth by more than 12 degrees from sunrise to sunset. Tracking of the solar elevation started 1 to 2 hours after sunrise and ceased 1 to 2 hours before sunset. On an overcast day, the laminas reoriented… (More)
Tendon attaches to bone across a functionally graded interface, "the enthesis". A gradient of mineral content is believed to play an important role for dissipation of stress concentrations at mature fibrocartilaginous interfaces. Surgical repair of injured tendon to bone often fails, suggesting that the enthesis does not regenerate in a healing setting.… (More)
Stomatal movements depend on both ion influx and efflux; attainment of steady state apertures reflects modulation of either or both processes. The role of Ca(2+) in those two processes was investigated in isolated epidermal strips of Commelina communis, using the Ca(2+) chelator EGTA to reduce apoplastic [Ca(2+)]. The results suggest that a certain… (More)
and anonymous referees for the BJPS. Arlin Stolzfus and Mark Ragan provided extremely helpful clarification of Haeckel's evolutionary claims. The National Science Foundation (SES-9906997) provided financial support.