FIGURE 5.

Intercepted photosynthetic photon flux density (PPFD) of lettuce canopy grown at three planting densities (low, middle, and high being 23, 37, and 51 plants m^–2). Solid lines represent with far-red radiation (FR) treatment (52 μmol m^–2 s^–1 FR) and dashed lines indicate treatment without FR. Light was cumulated from 14 to 28 DAT. Bars on top of each day represent least significant difference. Significant FR effect: ^∗P < 0.10, ^∗∗P < 0.05 and, ^∗∗∗P < 0.01. Data are means of two blocks (n = 2) each with four–six replicate plants.