Indigenous Australian grass seeds as grains: macrostructure, microstructure and histochemistry

Area of Science:

• Agricultural Science
• Botany
• Food Science

Background:

• Colonization has disrupted the traditional use of native Australian grasses for food by First Nations people.
• Revitalizing native grain systems requires understanding their unique properties for potential environmental, economic, nutritional, and cultural benefits.

Purpose of the Study:

• To characterize the grain structure and histochemistry of four Australian native grasses: Button Grass (Dactyloctenium radulans), Curly Mitchell Grass (Astrebla lappacea), Native Millet (Panicum decompositum), and Weeping Grass (Microlaena stipoides).
• To compare these properties with domesticated grains like wheat and sorghum.

Main Methods:

• Whole-grain imaging using stereo microscopy.
• Visualization of starch and embryo.
• Microscopic imaging (bright-field and fluorescence) of fixed grain sections.

Main Results:

• Native grains exhibited variations in shape, size, and color.
• Aleurone layer was typically one-cell thick, except in Weeping Grass (two-cell thick).
• Endosperm cell walls were thinner in native grains compared to wheat and sorghum; starch distribution varied, with most native grains having starch concentrated centrally, unlike Weeping Grass. Protein was abundant in aleurone/sub-aleurone layers, with Button Grass also showing protein-rich endosperm.
• Native species had proportionally larger embryos than wheat.

Conclusions:

• Significant differences in grain properties exist among native Australian grass species.
• These findings have implications for the agri-food industry, particularly in adapting to climate change and promoting Indigenous food systems.