Seed germination of Echinopsis schickendantzii (Cactaceae): the effects of constant and alternating temperatures

PABLO ORTEGA-BAES; GUADALUPE GALÍNDEZ; SILVIA SÜHRING; MARIANA ROJAS-ARÉCHIGA; MATTHEW I. DAWS; HUGH W. PRITCHARD

SEED SCIENCE AND TECHNOLOGY

ISTA-INT SEED TESTING ASSOC

Año: 2011 vol. 39 p. 219 - 224

0251-0952

The effects of constant and alternating temperatures on seed germination in the Cactaceae have been reported to vary, probably as a result of the different temperature regimes used and the species considered. We determined the cardinal temperatures and evaluated the effects of constant and alternating temperatures on seed germination of the South American cactus, Echinopsis schickendantzii Web, considering a wide range of constant and alternating temperatures. The base, optimum and maximum temperatures were 7ºC, 26.8ºC and 49ºC, respectively. Seed germination proportions and germination rates were not only significantly different at constant and alternating temperatures but also among all temperature regimes considered. The highest proportions occurred at 15°, 20°, 30º and 30/15ºC w hereas the highest germination rates occurred at 25º, 30º, 30/20º, 35/20º and 40/25ºC, with no significant differences between the highest values at constant and alternating temperatures. In the sub-optimal temperature range for germination rate, the thermal time to 50% germination was 98°C-days. The results indicate the seeds have no obligate requirement for alternating temperature for germination.