Freezing avoidance mechanisms in juveniles of giant rosette plants of the genus Espeletia

Abstract

Along soil-air gradients in tropical high mountains, plants growing at soil level tolerate frost while those growing well above ground, including all species in the genus Espeletia, use freezing avoidance mechanisms to survive low nighttime temperatures. The question that arises and the objective of this work were: What are the low temperature resistance mechanisms in giant rosettes when they are within the juvenile stages, i.e. closer to the ground? Juveniles of Espeletia spicata and Espeletia timotensis, dominant plants of the high Venezuelan Andes, were chosen for this study. To determine resistance mechanisms for these species, air and leaf temperatures were recorded in the field in 24 h cycles, while thermal analysis and injury temperature were determined in the laboratory. Both E. spicata and E. timotensis juveniles depend on avoidance mechanisms through a high supercooling capacity, permitting leaves to resist low nighttime temperatures. Minimum leaf temperatures were -4.9 and -5.1°C, for E. spicata and E. timotensis, respectively, occurring during the dry season. Ice formation occurred at -14.3 and -15.3°C for E. spicata and E. timotensis, respectively. Injury occurred at approximately -15°C in both species. Low temperature resistance mechanisms in juveniles are similar to those in adult plants.

Frost resistance in the tropical palm Euterpe edulis and its pattern of distribution in the Atlantic Forest of Argentina

“…Consequently, the initial rate of temperature decrease was not crucial for the process under study. Plants that supercool avoid the potentially damaging effects of cells dehydration during extracellular freezing (typical of plants that tolerate ice formation) but exhibit tissue damage when freezing occurs (Goldstein et al, 1985;Rada et al, 1985;Goldstein and Nobel, 1991;García-Varela and Rada, 2003). Consistent with this, the general pattern of damage and ice formation in plants that permanently supercool (sensu Larcher, 2003) ice formation in E. edulis was always followed by non-reversible tissue injury during the laboratory experiments.…”

Contribution of occult precipitation to the water balance of páramo ecosystems in the Colombian Andes

“…Their geographic location results in weather conditions dominated by low temperatures, high relative humidity, and low evapotranspiration, related to the low leaf area index (1.3 on average), permanence of low clouds, and frequency of fog (Azocar & Rada, ; Cavieres, Rada, Azócar, García‐Núñez, & Cabrera, ; García‐Varela & Rada, ; Rada, Azocar, Gonzalez, & Briceño, ). Because of the presence of low clouds, occult precipitation can be a significant water input to páramo ecosystems (Díaz‐Granados et al, ), therefore contributing to the high run‐off ratio recognized from these ecosystems (Tobón, ), understanding the run‐off ratio as the proportion between total inputs and the water yield from the basin (Hino, Odaka, Nadaoka, & Sato, ).…”

Does plant height determine the freezing resistance in the páramo plants?

“…The microclimate hypothesis is further compromised by the fact that even though adult individuals of the supposedly avoidant species experience milder microclimate they need to be able to survive the more extreme conditions near the ground as juveniles for many years. Although leaves of Espeletia juveniles resist lower freezing temperatures than the adult plants, they still use the same mechanism, that is, avoidance by supercooling (García-Varela & Rada 2003).…”