Question

Select the CORRECT option that shows the match between spectral bands and the factors affecting the spectral signature of vegetation at the leaf level.

Spectral bands	Factors affecting the spectral signature of vegetation at the leaf level
(P) Green	(i) Water content in the leaf
(Q) Red	(ii) Internal structure of the leaf
(R) Near Infrared	(iii) Absorption from chlorophyll
(S) Shortwave Infrared	(iv) Reflectance from chlorophyll

• A. (P)-(iv), (Q)-(iii), (R)-(ii) and (S)-(i)
• B. (P)-(iii), (Q)-(iv), (R)-(ii) and (S)-(i)
• C. (P)-(iv), (Q)-(iii), (R)-(i) and (S)-(ii)
• D. (P)-(iii), (Q)-(iv), (R)-(i) and (S)-(ii)

Hint:

Remember the leaf-level rule of thumb: SWIR relates to leaf water content, NIR relates to internal leaf structure, and the visible bands relate to chlorophyll, with red being absorbed strongly and green reflected relatively more.

Answer 1

The Correct Option is A

Step 1: Recall what controls leaf-level spectral response in each band.
At the leaf level, reflectance in the visible bands is controlled mainly by leaf pigments (chlorophyll a and b, carotenoids), reflectance in the near infrared (NIR) is controlled mainly by the internal cellular structure of the leaf (mesophyll cell walls and air spaces), and reflectance in the shortwave infrared (SWIR) is controlled mainly by the water content of the leaf.
Step 2: Assign the Shortwave Infrared (S) band.
Water has strong absorption bands in the SWIR region (around 1450 nm, 1950 nm and 2500 nm), so leaf reflectance here is governed by the leaf's water content. So \((S)\)-\((i)\).
Step 3: Assign the Near Infrared (R) band.
In the NIR region there is very little pigment or water absorption, so the high reflectance seen here is caused by multiple scattering of light at the cell wall to air-space interfaces inside the leaf. So \((R)\)-\((ii)\).
Step 4: Assign the Red (Q) band.
Chlorophyll a and b absorb strongly around 660 to 680 nm (the red region), which is why reflectance is very low there. So \((Q)\)-\((iii)\), absorption from chlorophyll.
Step 5: Assign the Green (P) band.
Chlorophyll absorbs comparatively less green light than red or blue light, so more green light is reflected back, producing the small green reflectance peak and the green color of healthy leaves. So \((P)\)-\((iv)\), reflectance from chlorophyll.
Step 6: Combine.
\((P)\)-\((iv)\), \((Q)\)-\((iii)\), \((R)\)-\((ii)\), \((S)\)-\((i)\), which is option (A). \[ \boxed{\text{Option (A)}} \]