Análisis de la productividad en caña de azúcar. III. Respiración en la oscuridad de hojas y tallos de cinco variedades de caña de azúcar y pérdidas nocturnas de materia seca

Abstract

Daily respiration rates of leaves and stems of the sugar cane varieties ´B 49119´, ´B 4362´, ´B60125´, ´B 54124´and ´PR 980´were not significantly different. Varieties ´PR 980´and ´B 4362´had higher night respiration rates, therefore and increase in yield is to be expected when they are cultivated in zones with a wide daily temperature amplitude. The respiration rate of leaves and stems strongly decreased with crop age. Leaves of the same age produced at different times during the year showed a characteristic reduction in respiration rate. The leaves in sugar cane PR 980´ had a negative photosynthetic balance when under the 10 per cent level of day light. The stems of ´PR 980´also showed a reduction in respiration rate during the growth period. Respiration or internodes diminished with their age and that of the whole plant. The node zone had a respiration rate 2-3 times higher than that of the internodes, this contribution was not taken into account in the computation of respirational losses of organic matter. Nevertheless, the computations were a good estimate of those losses. The variation in organic matter losses through respiration during the growth period is indicated; only after 280 days the losses reached the 60 per cent levels. When the maximun growth rate was reached, night respiration losses of organic matter determined a reduction of about 60 per cent of the total production