SUMMARYFive short varieties of spring wheat derived from Norin 10: Lerma Rojo 64A (R), Penjamo 62 (P), Sonora 64 (S), Mexico 120 (M), and an unnamed selection obtained from Mexico (X), had grain yields equal to, or only slightly less than those of the taller European spring varieties Kloka (K) and Jufy I (J). Yields ranged from 500 to 580 g/m2 of dry matter. The short variety NBJ115 (N) was severely infected with yellow rust and yielded only 290 g/m2. Total dry weight (excluding roots) of the short varieties was less than of J and K; hence grain accounted for 49 % of the total for the short varieties and 42 % for J and K. Most of the short varieties had fewer ears than the tall ones because sowing difficulties and poor germination produced fewer plants. The relative yields of X, P, R and S seemed to be correlated with their plant and ear densities.Leaf area duration after flowering (D), based either on total green area or on green area above the flag‐leaf node only, was less for the short varieties than for J and K. The apparent mean efficiency of this area in grain production (grain yield divided by D) was 50% greater for the short than for the tall varieties.The height of the short varieties ranged from 43 cm (M) to 79 cm (N). K was 92 cm and J 97 cm tall. Differences in height depended on the lengths of the top four internodes and not on number of internodes. Main shoots of all varieties produced seven or eight leaves. All varieties initiated spikelets 45–48 days after sowing. The short varieties flowered 103 days and matured 155 days after sowing; J and K flowered and matured about 1 week earlier.
Summary
Changes in nitrate reductase activity in response to nitrogen treatment were measured in vivo in the basipetal part of the youngest ligule emergent leaf of wheat plants during early development. The relationship between these measurements and grain yield is reported for some spring wheats grown in a growth room and some field‐grown winter wheats. In both situations the c correlation of a linear regression of yield parameters and single measurements of nitrate reductase was found to be significant. Where split dressings of nitrogen were applied the seasonal mean nitrate reductase activity correlated well with yield.
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