Changes in IAA responsiveness in the elongation region of graviresponding mung bean roots.

IAA responsiveness of sections of root tissue taken from the top and bottom of mung bean roots was assessed prior to and at varying times following gravistimulation. Prior to gravistimulation, root tissue sections from the sides of the elongation zone responded similarly to IAA. After gravistimulation (within 5 min), root sections from the bottom of the elongation zone became more responsive to IAA than sections collected from the upper side of the elongation zone.

The effects of asymmetric calcium application on primary root curvature of ageotropum pea mutant.

Recent studies indicate that roots of ageotropum seedlings can be used to study the hydrotropic response of roots independent of physiological events related to the gravity response of roots. There is evidence that Ca2+ ions are important in both the gravitropic and hydrotropic response of roots. In this study, we have compared three fully graviresponsive pea cultivars and the ageotropum mutant with regard to: 1) general root anatomy, 2) the effects of unilateral Ca application to both the root cap and DEZ region on root curvature, and 4) effects of unilateral application of EGTA to the DEZ region.

Characterization of hydrotropism: the timing of perception and signal movement from the root cap in the agravitropic pea mutant ageotropum.

In recent years, experiments have demonstrated that the gravity response of roots can be separated from the hydrotropic response by using the agravitropic pea mutant ageotropum. Though this mutant has been a useful tool for demonstrating the existence of the hydrotropic response of roots, little is known about how perception, transduction, transmission, and the growth response is accomplished. In this study, we have used the ageotropum mutant to investigate both the threshold time for perception of an osmotic stimulation and the minimum time required for signal transduction and transmission in roots following an osmotic stimulation at the root cap.

Characterization of hydrotropism: the timing of perception and signal movement from the root cap in the agravitropic pea mutant ageotropum.

In this study, ageotropum pea mutant was used to determine the threshold time for perception of an osmotic stimulation in the root cap and the time requirement for transduction and transmission of the hydrotropic signal from the root cap to the elongation region. The threshold time for the perception of an osmotic stimulation was compared to current estimates of threshold times for graviperception in roots. The time required for transduction and transmission in the hydrotropic response of ageotropum was compared to the time requirement in the gravity response of Alaska pea roots.

Effect of calmodulin antagonists on the growth and graviresponsiveness of primary roots of maize.

We examined the effect of calmodulin (CaM) antagonists applied at the root tip on root growth, gravity-induced root curvature, and the movement of calcium across the root tip and auxin (IAA) across the elongation zone of gravistimulated roots. All of the CaM antagonists used in these studies delayed gravity-induced curvature at a concentration (1 micromole) that did not affect root growth. Calmodulin antagonists (> or = 1 micromole) inhibited downward transport of label from 45Ca2+ across the caps of gravistimulated roots relative to the downward transport of 45Ca2+ in gravistimulated roots which were not treated with CaM antagonists.