Conversion efficiency and maintenance coefficient in the whole plant, roots and tops in maize and rice under aluminum stress

Abstract

The effects of aluminum (AD on the conversion efficiency and maintenance respiration coefficient of whole structure planta and their organs, roots and tops, were studied in two rice cultivars (Oryza sativa L.), IAC- 165 (tolerant) and IAC-899 (sensitive), and two maize hybrids (Zea mays L.), HS1227 (tolerant) and HS7777 (sensitive), through the carbon balance technique. Under Al stress the sensitive cultivars had a reduction of approximately 20% in the gross photosynthesis production and growth rate; for the tolerant plants such parameters practically were not affected. Under Al stress, all cultivars, both sensitive and tolerant, had the plants, roots and tops' respirations reduced in comparison with the non stressed ones. The root conversion efficiency (YR), in all cultivars under Al stress, increased by 12% to 16%, while the top conversion efficiency (A) practically was not affected. The increase in YR was about the same, both for tolerant and non tolerant cultivars, and for such it was not possible to use it for screening plants. The maintenance respiration coefficient also showed no relationships with tolerance to Al toxicity.