Complex, non-monotonic dose-response curves with multiple maxima: Do we (ever) sample densely enough?

Area of Science:

• Plant biology
• Biochemistry
• Cellular signaling

Background:

• Biological dose-response curves are typically expected to be monotonic or have a single peak.
• Deviations from simple curves are often dismissed as experimental noise.
• Previous studies have hinted at complex dose-response patterns in various biological systems.

Purpose of the Study:

• To investigate the detailed dose-response relationships of plant tissue cultures to various exogenous substances.
• To determine if complex, non-monotonic dose-response curves are reproducible and statistically significant.
• To explore the implications of these complex curves for understanding biological phenomena.

Main Methods:

• Utilized plant primary tissue cultures (kale and tobacco stem pith explants).
• Exposed cultures to varying concentrations of sucrose, cytokinins (benzyladenine [BA], kinetin), and auxins (indole-3-acetic acid [IAA], naphthaleneacetic acid [NAA]).
• Measured growth and several biochemical parameters to construct dose-response curves.

Main Results:

• Observed multiple, reproducible, and statistically significant maxima in dose-response curves for growth and biochemical parameters.
• Demonstrated complex, non-monotonic dose-response patterns across a wide range of tested substance concentrations.
• These complex patterns were consistent across different plant species and tested substances.

Conclusions:

• The findings suggest a previously underappreciated class of biological phenomena characterized by periodic patterns in dose-response curves.
• These complex curves, with multiple maxima and minima, challenge traditional dose-response expectations.
• Further research is needed to elucidate the underlying mechanisms driving these complex biological responses, potentially requiring higher sampling frequencies in studies.