Screening of Genotypes ofBrassica junceaL. for Leaf Conductance under Field Conditions

Abstract

Twenty-three genotypes of Indian mustard were studied for leaf conductance (K1) at the floral bud initiation stage under non-stress conditions. The comparison of leaf conductance and of several other measurements in the standard cultivar ‘Prakash’ demonstrated that a screening procedure could be developed for leaf conductance prior to the flowering stage of mustard grown in the field. Errors due to short term environmental fluctuations and to ontogenetic drift in conductance can be reduced if the measurements are made on both the ad- and abaxial surfaces of the uppermost expanded leaf between 1200 h and 1400 h on clear days. Irradiance levels can be neglected once a value of photosynthetically active radiation (PAR) of about 1000 μE m−2 s−1 at the adaxial surface or of 1200 μE m−2 s−1 at the crop canopy has been reached. The water status of the plants is of no importance as long as the plants are not under undue stress. The different genotypes showed a genetic variability of 243% in leaf conductance.