Figure 4.

Photosynthetic physiology of canopy basipetal three leaves of super early-season rice leaves under different nitrogen applications. (A, B) SPAD value; (C, D) net photosynthetic rate (Pn). Different letters show significant differences between nitrogen applications at 5% probability level. Tillering stage data was measured on May 22^nd, panicle initiation stage date was measured on June 4^th, grain filling stage date was measured on June 27^th. 6 replications were measured for each treatment.