Ungerminated Rice Grains Observed by Femtosecond Pulse Laser Second-Harmonic Generation Microscopy

Area of Science:

• Plant Science
• Biophysics
• Materials Science

Background:

• Rice grain composition influences germination and nutritional value.
• Understanding starch and sugar distribution is crucial for plant science.
• Nonlinear optical microscopy offers novel imaging capabilities for biological tissues.

Purpose of the Study:

• To demonstrate the utility of second-order nonlinear optical microscopy for rice grain analysis.
• To visualize the distribution of starch types and sugars in rice grains.
• To investigate the role of sugars in rice germination.

Main Methods:

• Second-harmonic generation (SHG) microscopy was employed to image rice grains.
• Images were compared with traditional iodine staining of starch granules.
• Amylose-free glutinous and amylose-containing nonglutinous rice varieties were analyzed.

Main Results:

• SHG microscopy successfully differentiated starch types in rice grains.
• Distinct distributions of starch and sugars were observed in the embryo-facing endosperm region (EFR).
• Crystallized glucose or maltose were detected on the testa side of the embryo, suggesting their role in germination.

Conclusions:

• SHG microscopy is a powerful tool for rice grain science.
• The distribution of sugars and amylopectin in rice grains can be monitored using SHG.
• Findings provide insights into the initial stages of rice germination.