High Temperatures and Net CO2 Uptake, Growth, and Stem Damage for the Hemiepiphytic Cactus Hylocereus Undatus

• Published in: Biotropica Vol. 34; no. 2; pp. 225 - 231
• Main Authors: Nobel, P S, De la Barrera, E
• Format: Journal Article
• Language: English
• Published: 01.06.2002
• Subjects: Hylocereus
• ISSN: 0006-3606
• DOI: 10.1043/0006-3606(2002)034(0225:HTANCU)2.0.CO;2

Hylocereus undatus, which is native to tropical forests experiencing moderate temperatures, would not be expected to tolerate the extremely high temperatures that can be tolerated by cacti native to deserts. Nevertheless, total daily net CO2 uptake by this hemiepiphytic cactus, which is widely cultivated for its fruits, was optimal at day/night air temperatures of 30/20 degree C, temperatures that are higher than those optimal for daily net CO2 uptake by cacti native to arid and semiarid areas. Exposure to 35 /25 degree C for 30 weeks led to lower net CO2 uptake than at 10 weeks; exposure to 40/30 degree C led to considerable necrosis visible on the stems at 6 weeks and nearly complete browning of the stems by 19 weeks. Dry mass gain over 31 weeks was greatest for plants at 30 /20 degree C, with root growth being especially noteworthy and root dry mass gain representing an increasing percentage of plant dry mass gain as day/night air temperatures were increased. Viability of chlorenchyma cells, assayed by the uptake of the vital stain neutral red into the central vacuoles, was decreased 50 percent by a one-hour treatment at 55 degree C compared with an average of 64 degree C for 18 species of cacti native to deserts. The lower high-temperature tolerance for H. undatus reflected its low high-temperature acclimation of only 1.4 degree C as growth temperatures were raised by 10 degree C compared with an average acclimation of 5.3 degree C for the other 18 species of cacti. Thus, this tropical hemiepiphytic cactus is not adapted to day/night air temperatures above ca 40/30 degree C, although its net CO2 uptake is optimal at the relatively high day /night air temperatures of 30/20 degree C.Original Abstract: Cabe esperar que Hylocereus undatus, una especie nativa del bosque tropical expuesta a temperaturas moderadas, no sea capaz de tolerar las temperaturas extremadamente altas que toleran los cactus nativos del desierto. Sin embargo, la asimilacion diaria neta optima de CO2 de esta cactacea hemiepifita, ampliamente cultivada por sus frutos, ocurrio a temperaturas ambiente de 30/20 degree C (diurna /nocturna); mismas que son mayores que las de los cactus nativos de zonas aridas y semiaridas. Un regimen de temperaturas de 35/25 degree C durante 30 semanas condujo a una asimilacion neta de CO2 menor que aquella registrada a las 10 semanas; un regimen de 40/30 degree C condujo a una necrosis considerable, visible en los tallos a partir de la sexta semana, que se extendio hasta cubrirlos casi totalmente a las 19 semanas. Despues de 31 semanas el incremento en peso seco fue mayor en las plantas sometidas a 30/20 degree C, el crecimiento de la raiz fue especialmente notable y represento una proporcion creciente del peso seco conforme las temperaturas diurna/nocturna se elevaron. La viabilidad de las celulas del clorenquima, determinada mediante la incorporacion in vivo de la tincion rojo neutro en las vacuolas centrales, disminuyo 50 por ciento despues de una hora a 55 degree C, comparada con el promedio de 64 degree C registrado para las otras 18 cactaceas nativas del desierto. La escasa tolerancia de H. undatus a temperaturas elevadas se reflejo en una aclimatacion minima de solo 1.4 degree C, cuando la temperatura se elevo 10 degree C durante su crecimiento; las otras 18 especies de cactus presentaron una aclimatacion promedio de 5.3 degree C. Por lo tanto, esta cactacea hemiepifita, no esta adaptada a temperaturas diurna/nocturna superiores a los 40/30 degree C, a pesar de que su asimilacion neta optima de CO2 ocurre a temperaturas relativamente altas de 30/20 degree C.