02449naa a2200337 a 450000100080000000500110000800800410001902200140006002400570007410000230013124500960015426000090025052014880025965000150174765000300176265000090179265000100180165000260181165000140183765000140185165000160186565000170188165300290189865300140192765300140194165300240195570000180197970000200199770000160201777300780203312082802022-04-07       2000    bl uuuu     u00u1 u    #d  a0100-204X7 ahttps://doi.org/10.1590/S0100-204X20000010000042DOI1 aPINHEIRO, B. da S.  aCarbon isotope discrimination and yield of upland rice as affected by drought at flowering.  c2000  aField experiments involving upland rice genotypes, sown in various dates in late season, were carried out to assess the relationship of carbon isotope discrimination with grain yield and drought resistance. In each one of the three years, one trial was kept under good water availability, while other suffered water shortage for a period of 18-23 days, encompassing panicle emergence and flowering. Drought stress reduced carbon isotope discrimination measured on soluble sugars (Ds) extracted from stem uppermost internode at the end of the imposition period, but had relatively less effect on bulk dry matter of leaves, sampled at the same period, or that of uppermost internodes and grains, sampled at harvest. The drought-induced reduction in Ds was accompanied of reduced spikelet fertility and grain yield. In the three trials subjected to drought, genotypes with the highest yield and spikelet fertility had the lowest Ds. However, this relationship was weak and it was concluded that Ds is not a sufficiently reliable indicator of rice drought resistance to be useful as a screening test in breeding programs. On the other hand, grain yield and spikelet fertility of genotypes which were the soonest to reach 50% flowering within the drought imposition period, were the least adversely affected by drought. Then, timing of drought in relation to panicle emergence and to flowering appeared to be a more important cause of yield variation among genotypes than variation in Ds.  aInternodes  aOryza sativa endornavirus  aRice  aArroz  aDeficiência Hídrica  aEntrenós  aEspigueta  aFertilidade  aOryza Sativa  aFertilidade da espigueta  aFertility  aSpikelets  aSpikelets fertility1 aAUSTIN, R. B.1 aCARMO, M. P. do1 aHALL, M. A.  tPesquisa Agropecuária Brasileiragv. 35, n. 10, p. 1939-1947, out. 2000.