On the relation between photo- and gravitropically induced spatial memory in maize coleoptiles

Area of Science:

• Plant biology
• Tropism research
• Gravitational biology

Background:

• Phototropism and gravitropism are key plant growth responses.
• Understanding their interaction is crucial for plant development.
• Maize coleoptiles exhibit complex responses to directional stimuli.

Purpose of the Study:

• To investigate the interaction between phototropic and gravitropic stimulation in maize coleoptiles.
• To analyze the stability and directionality of tropistic responses.
• To explore gravity-induced inhibition of phototropic responses and directional memory.

Main Methods:

• Analyzing coleoptile curvature under rotation on horizontal clinostats.
• Applying phototropic (blue light) and gravitropic (gravity) stimuli.
• Varying time intervals between gravistimulation and photostimulation.
• Testing directional memory using sequential light pulses.

Main Results:

• Gravitropic curvature was transient and reoriented towards the caryopsis.
• Phototropic stimulation resulted in stable curvature and orientation.
• Gravistimulation inhibited phototropic responses after 90 minutes, but only within the plane of gravity stimulation.
• Gravity appeared to induce a directional memory distinct from phototropic memory.

Conclusions:

• Gravitropism in maize coleoptiles is unstable and influenced by nastic curvature.
• Phototropism is a stable response, but can be inhibited by prior gravistimulation.
• Distinct mechanisms likely mediate gravi- and phototropic directional memories, diverging early in signal transduction.