The impact of cardinal temperature variation on the germination of Haloxylon aphyllum L. seeds

Abstract

Seed germination is a biological process that is affected by a variety of genetic and environmental factors. The cardinal temperature and thermal time are required for germination. The principal objective of this study was to identify and characterize variations in the base, optimum, and maximum germination temperatures of Haloxylon aphyllum L. from two seed sources, in order to establish models for use in predicting seeding dates. Mature H. aphyllum seeds were germinated at temperatures between 5 and 35ºC. The germination behavior of H. aphyllum seeds to different temperature regimens in light was evaluated over a temperature range of 5-35ºC at intervals of 5ºC. The rate of germination increased between base and optimum thermal conditions, and decreased between optimum and maximum thermal conditions; the germination rate varied in a linear fashion at both sub-optimal and supra-optimal temperatures. The linear regression fit the range of germination rates at 5ºC to 25ºC and 25ºC to 30ºC, and thus the base temperature, optimum temperature, and maximum temperature for the germination of H. aphyllum were measured to be 0.6ºC, 25.69ºC, 37.90ºC, and 1.76ºC, 21.56ºC, 37.90ºC for Qom and the Fars dune desert respectively.

CARDINAL TEMPERATURES FOR GERMINATION OF THE MEDICINAL ANDDESERT PLANT, Calotropis procera

“…Taghvaei et al (2010) reported similar results about the germination rate responses of Haloxylon aphyllum Khaef et al (2010) reported that the optimal temperature for the germination of Calotropis procera was 25 o C, and pointed out that germination increased until 35 o C and then decreased.…”

“…The base temperatures were 20 o C and 19 o C in the Zahedan and Fars desert regions, respectively (Table 3). The range in base temperatures between two seed lots of milkweed (Calotropis procera) was 0.62 o C and 1.76 o C, but was not statistically significant, although it may be biologically significant (Taghvaei et al, 2010). Cardinal temperatures for germination of the medicinal and ...…”

“…Cardinal temperature was calculated on the basis of the responses of the germination rate to temperature (Taghvaei et al, 2010). An intersecting-line model (Al-Sobhi et al, 2006) was employed.…”

“…Hardegree (2006) predicted the cardinal temperatures of germination for four rangeland grass species using a regression method. Taghvaei et al (2010) generated a model for predicting the cardinal temperature of milkweed (Calotropis procera). The cardinal temperatures for germination have been determined via the use of germination rate for different plants (Rizzardi et al, 2009).…”

“…Regression analysis is generally recognized as the best statistical tool for the investigation of relationship among these variables. The data collected at sub-optimal and supra-optimal temperatures was used to construct two linear regressions to describe the increases and decreases in the germination rate at suboptimal and supra-optimal temperatures, respectively by Taghvaei et al (2010). The optimum temperature is the temperature at which these two lines intersect (Covell et al, 1986).…”