Maize water content and solute potential at three stages of development

Maize (Zea mays L.) productivity is highly sensitive to water stress at flo wering, but selection for water stress tolerance might be performed more ef ficiently during vegetative growth. To test the consistency of rank for rel ative water content (RWC) and solute potential (Psi(s)) at different stages of development, 15 S-4 and 2 inbred maize lines were sampled for midday RW C determined by a modified method (mRWC) and solute potential normalized to 100% mRWC (Psi(s100), = Psi(s) X mRWC / 100) at vegetative, flowering, and kernel development. Both mRWC and Psi(s100) varied significantly among gen otypes. Midday mRWC was significantly correlated between vegetative and flo wering (r = 0.72**, P = 0.01), but not between vegetative and kernel develo pment or flowering and kernel development stages. However, there was no sig nificant correlation of Psi(s100) among vegetative, flowering, and kernel d evelopment stages. Date of anthesis was used as an index of maturity and wa s significantly correlated with mRWC and Psi(s100) at certain stages (mRWC: vegetative r = 0.27*, kernel development r = -0.50** and Psi(s100): vegeta tive r = -0.30*, flowering r = 0.39**, kernel development r = 0.54**). In a related experiment, 48 S-4 and four inbred lines were sampled for change i n RWC Delta mRWC and change in Psi(s100) (Delta Psi(s100)) by detached leav es of field-grown plants. The Delta Psi(s100) and Delta mRWC varied signifi cantly among lines. Date of anthesis was correlated with Delta mRWC (r = -0 .19*), but not Psi(s100). We conclude that the rank of maize genotypes for mRWC and Delta Psi(s100) may be affected by the degree of development and s election should be performed on plants sampled at equivalent maturities.