Maize leaf rolling initiation

Maize plants of CPB2 and CPB8 hybrids were kept under water deficit for 22 d, In the CPB8 hybrid, leaf rolling initiated at the 9(th) d of water deficit period, while in CPB2 hybrid it was at the 15(th) d, Both hybrids showed leaf rolling initiation at the same leaf water potential, Psi(w) of -0.480+/-0.095 MPa. At leaf rolling initiation, the leaf osmotic potential, Psi(s) was -0.730+/-0.085 MPa in CPB8 and 0.630+/-0.110 MPa in CPB2, The leaf temperature and stomatal conductance were higher in CPB8 than in CPB2. Values of leaf Psi(w), ribulose-1,5-bisphosphate carboxylase activity, chlorophyll content, and specific leaf area were similar in both hybrids. Phosphoenolpyruvate carboxylase activity and protein content were lower in the CPB2 hybrid than in CPB8, In both hybrids leaf rolling initiation was associated with: (1) higher leaf temperature, with leaf rolling effect related to leaf temperature reduction, and (2) lower leaf Psi(s), related to osmotic adjustment as an additional component of drought-tolerance strategy.