**2.10 Effect of rice husk biochar on proline of maize under drought stress**

Proline is a kind of stress protein. Proline accumulation under stress condition occurred because the Calvin cycle of photosynthesis is affected by drought; as a result N content could not be properly metabolized. In drought soil biochar increases photosynthesis and proper metabolism of N content. Proline content of maize varied significantly with different doses of biochar under drought conditions (**Figure 4**).

Under control condition (80% of FC), 60% of field capacity, and 40% of field capacity, lowest proline contents were 1.1, 1.1, and 3.2 μ mole/g, respectively, when biochar was applied at 20 t/ha, and highest proline contents were 1.8, 2.9, and 6.1 μ mole/g, respectively, when no biochar was applied. [40] reported biochar decreased proline content in plants. [41] marked drought stress caused overproduction of proline content. [42] also reported biochar increased photosynthesis in grape leaves.
