Polarity of root statocytes--relevance for graviperception

Area of Science:

• Plant biology
• Cell biology
• Gravitational biology

Background:

• Statocytes in cress (Lepidium sativum L.) root caps exhibit structural polarity during radicle outgrowth.
• This polarity involves specific positioning of the nucleus and endoplasmic reticulum (ER) complex.
• Amyloplasts sediment on the ER complex, a key feature in gravity sensing.

Purpose of the Study:

• To investigate the development and regulation of structural polarity in plant root cap statocytes.
• To determine the role of the cytoskeleton in establishing and maintaining this polarity.
• To assess the impact of altered polarity on the plant's ability to perceive gravity.

Main Methods:

• Utilized clinostats (fast and slow rotating) to simulate microgravity conditions.
• Grew cress roots under actual microgravity in orbit.
• Applied drugs affecting microtubules and microfilaments to disrupt cellular structures.
• Observed statocyte structure and polarity using microscopy.

Main Results:

• Statocyte structural polarity develops independently of gravitational forces.
• Cytoskeleton (microtubules and microfilaments) plays a vital role in positioning the ER.
• Disrupting structural polarity via drugs or mechanical stimuli (rotation, centrifugation) impairs gravity perception.

Conclusions:

• Plant root cap statocyte polarity is an intrinsic developmental process, not solely gravity-dependent.
• The cytoskeleton is essential for establishing and maintaining the polarized structure of statocytes.
• Altering statocyte polarity directly affects the root's gravitropic response, highlighting its functional significance.