Question

On which factors does the reflectance from vegetation depend? Explain.

Hint:

Remember the 3 biological layers: The surface color (pigments), the inside structure (cells), and the plant's "thirst" (water).

Answer 1

Step 1: Concept
Spectral reflectance from vegetation is the cornerstone of agricultural remote sensing, allowing satellites to monitor crop health.

Step 2: Meaning
The amount of electromagnetic radiation (EMR) reflected by a plant changes dramatically depending on the plant's internal biology and physical structure across different wavelengths.

Step 3: Analysis

• Pigmentation (Visible Light): The presence of chlorophyll heavily dictates reflectance in the visible spectrum. Chlorophyll strongly absorbs blue and red light for photosynthesis, while reflecting green light, which is why healthy plants appear green.
• Internal Cell Structure (Near-Infrared): The structure of the spongy mesophyll cells inside the leaf strongly scatters and reflects Near-Infrared (NIR) energy. High NIR reflectance is the primary indicator of a healthy plant structure.
• Moisture Content (Shortwave Infrared): The amount of water stored in the plant tissues controls reflectance in the Shortwave Infrared (SWIR) bands. Higher water content leads to high absorption (and lower reflectance) of SWIR energy.

Step 4: Conclusion
Vegetation reflectance is governed by three primary biological factors: pigments, cell structure, and water. Final Answer: It depends on leaf pigmentation (chlorophyll for visible light), internal cellular structure (mesophyll for Near-Infrared), and moisture content (water for Shortwave Infrared).