Summary Blood oxygen affinities, erythrocytic nucleoside triphosphate concentrations (NTP) and other hematological parameters were measured in facultative air-breathing fish from the Amazon after acclimation to well aerated ("normoxic") and hypoxic water (PO2 = 125 to 135 and 20 to 25 mm, respectively). In the armored catfish Hypostomus sp, and Pterygoplichthys sp., hypoxia induces intermittent surfacing to gulp air and results in lower NTP levels, chiefly through significant decreases in guanosine triphosphate (GTF). The subsequent increases in blood O2 affinity appear adaptive to lowered time average internal O2 tensions. No similar changes were seen in the eel Synbranchus which breathes air almost continuously when kept in hypoxic water. The results are discussed in terms of their adaptive significance, and compared with data on temperate fish. | Resumo Afinidades pelo oxigênio do sangue, concentrações eritrocíticas de nucleosídeo trifosfato (NTP) e outros parâmetros hematológicos, foram medidos em peixes de respiração aérea facultativa do Amazonas, depois da aclimatação em água oxigenada ("normóxica") e água hipóxica (PO2 = 125 a 135 e 20 a 25 mm Hg, respectivamente). No bagre, Hipostomus sp. e Pterygoplichtys sp. a hipoxia leva a interminentes subidas à superfície para tomar ar, resultando em níveis mais baixos de NTP, principalmente pelo significativo decréscimo de guanosina 3-fosfato (GTF). Os subseqüentes aumentos na afinidade pelo O2 do sangue aparecem adaptados às tensões de O2 internas médias em tempos mais baixos. Nenhuma troca semelhante foi vista na enguia Synbranchus, a qual respira quase que continuamente ar, quando mantida em água hipóxica. Os resultados, são discutidos em termos de sua significância adaptativa e comparada com os dados sobre a temperatura do peixe.

Grain and aerial dry matter production and the number of pods per plant were found to be maximum in the '27-R' cultivar of Phaseolus vulgaris L, a red bean grown in the tropics, when the maximum soil moisture suction was 0.8 bars at 5 cm depth or 0.6 bars at 15 cm depth. The experiment was carried out in 26 liter pots of fumigated soil in a greenhouse at CATIE, Turrialba, Costa Rica, with plant spacing similar to field conditions. When the maximum suctions were greater or lesser than the optimum yield value, there was a reduction in yield. It was found that grain production loss per unit bar of suction change when the cyclic maximum suctions were less than the optimum value, were 15 times greater than the rate of production loss when the values were greater than the optimum. No disease nor pest problems were encountered during the study. Potential evapotranspiration increased to a maximum at the eight week and subsequently decreased. Evapotranspiration decreased with increasing maximum suction.