UNTERSUCHUNGEN ÜBER DIE GESCHWINDIGKEIT DES WASSERAUFSTIEGES IM SPROFI UND DEN BLATTFLÁCHENZUWACHS VON COFFEA ARABICA L. UND CITRUS AURANTIUM SINENSIS ENGLER IN VERSCHIEDENEN KLIMAZONEN KOLUMBIENS

Abstract

The total increase of leaf area and the rate of water movement in the stems of Coffea arabica L. and Citrus aurantium sinensis Engler were deter- *) Gekürzte Fassung einer am 18. 12. 1969 von der Naturwissenschaftlichen Fakultat der Universitát Giessen als Dissertation angenommenen Abhandlung. mined in various climatic regions of Columbia. During the rain season the maximum rate of water transport decreased with increasing height above sea level. This effect was observed to be more evident in Citrus than in Coffea. At the end of the dry season however, the maximum rate of water movement was measured in 1250 m (Citrus) and 1850 m (Coffea) above sea level. In case of sunshine the maximum values were higher than in case of clouded sky. The most considerable increase of total leaf area was reached at Coffea in 1850 m and at Citrus in 1250 m respectively. With reference to the water economy the cultivation of Citrus could be forced in sea levels about 1250 m with simultaneous displacement of Coffea cultivation to colder climatic regions. Diurnal variations showed, that if the intensity of radiation increased suddenly, the rate of water movement in the stems of Citrus trees accordingly increased. With Coffea trees different results were obtained. During the morning the rate of water transport in trees always increased. At noon the values either remained high or varied in irregular intervals. Moreover, in the hot climatic regions diurnal variations sometimes showed two maximums of rate of water flow in the stems of Coffea arabica. Above all, the type of observed diurnal variations depended on the sea level distance of the measuring point, the season, the intensity of radiation and the species of plant.