Two sets of disomic substitution lines, derived from the cultivars ÔPrestoÕ and ÔRhinoÕ of triticale, with rye chromosome pairs replaced by their wheat D-genome homoeologues, were tested in hydroponic culture for nitrogen and phosphorus uptake and utilization efficiency. The effect of a substitution on the amount of absorbed nutrients was predominantly negative and proportional to the effect on plant dry matter. Significant decreases were found for the substitutions 5D(5R), 6D(6R) of both cultivars, 2D(2R), 4D(4R) of ÔPrestoÕ and 3D(3R) of ÔRhinoÕ. On the other hand, the nitrogen utilization efficiency was significantly increased in all substitution lines, with the exception of the 1D(1R) ones. The differences in phosphorus utilization were generally positive, but less pronounced, and significant only in the lines 2D(2R) and 6D(6R). The data suggest that presence of both rye and D-genome chromosomes is conducive for the best effect of the applied N and P fertilizers.

No abstract

Iron starved dicotyledonous plants undergo several modification aimed at increasing iron assimilation, including enhanced plasma-membrane linked redox activities in roots (1). Monocots are known to regulate their iron requirement mainly by release of phytosiderophores. However a plasma-membrane associated Fe3+-ehelate reduetase activity exists in maize and is modulated by iron starvation. This increase is partly a consequence of the more abundant plasma membrane material found as part of an iron starvation syndrome affecting also root morphology (fresh mass +30 %). Molecular mass determinations of solubilized plasma-membrane or microsomes by means of FPLC size-exclusion chromatography identify a 210 kDa protein in both control and stressed material solubilized with 2 % (m/v) lysopbophatidylcholine. This protein appears to be very sensitive to freezing-thawing, high salt and dilution. After exposure to such conditions the activity is partially recovered (25 %) associated to 43 and 26 kDa forms tentatively identified as subunits of the 210 kDa (see also refs. 2,3). Other detergents directly give rise to such low molecular mass forms. These are also found in the supernatant fraction.

The accumulation and utilization efficiency of nitrogen and phosphorus were studied using hydroponic cultures of seedlings of the ‘Presto’ and ‘Rhino’ D(A) and D(B) substitution lines of hexaploid triticale. The results were significantly affected by homoeology group of chromosomes participating in a substitution, the A or B genome origin of replaced chromosome and genetic background of triticale cultivar. The substitutions 4D(4B) and 5D(5B) resulted in an increase of plant dry matter in relation to the non-substituted cultivars. The significant increase of N accumulation was found in 3D(3A) and 4D(4B) of ‘Rhino’, and 5D(5B) and 4D(4B) of ‘Presto’. The improvement of N utilization efficiency was recorded for 2D(2A) and 1D(1B) of ‘Presto’, and 5D(5B), 7D(7A) and 5D(5A) of ‘Rhino’. The P accumulation was distinctly improved in ‘Presto’ 5D(5B) substitution. The P utilization efficiency was improved in all substitutions containing 4D or 6D as well as in ‘Presto’ 2D(2B) and 5D(5B).