Germination responses of a non‐dormant seed population of Amaranthus patulus Bertol. to constant temperatures in the sub‐optimal range

Abstract

The germination responses of a nondortnant seed population of Amaranthus patulus Bertol. at constant sub-optimal temperatures in the range of I0-34°C wete analysed through a detailed time-course study. Although a final germination percentage of nearly 100% was attained at temperatures above 18°C, it fell abruptly to zero with decreasing temperature frotn 17 to 10°C. The final germination percentage v. temperature plotted on a normal probability scale yielded a straight line, indicating normality of the lower limit temperature within seed population with an estimated mean of 13.75°C and a standard deviation of 1.50°C. Simple linear relationships were obtained between the temperature and the germination rates, i.e., the reciprocals of the time taken to germinate by the subpopulations with 20-80% germination. The linear relationships were characterized by similar base temperatures or theoretical litnit temperatures of about 11°C but there was a variation in the required 'thermal times' {Q), the distribution of which could be approxitnated for the seed population by the following distribution function: i/.n3 1 iv 1/ 2 where m is the median of the distribution and A is a parameter characterizing the pattern of the distribution. When the gertnination rates were calculated after subtracting 10-14 h ftom the time actually consutned in gertnination, linear Arrhenius relationships were obtained. The appatcnt activation energy estimated from the linear regression of Arrhenius plots was approximately lOOkJmol"' with all 20-80% subpopulations.

Germination responses of a seed population of Taraxacum officinale Weber to constant temperatures including the supra‐optimal range

“…Experimental procedures wete the same as described in the previous paper (Washitani & Takenaka 1984a), and time eourses ofthe cutnulative germination of six replieations of 50 seeds utider the various constant temperatures of 7-34 °C were measured using temperature-eontrolled incubators in which tetnperature variation was less than +0.1 "C.…”

“…To analyse the temperature-dependency of the germination rate and its spread among the seeds, subpopulations were identified and characterized by cumulative percentages of 20-80% (Washitani & Takenaka, 1984a), The rate of germination was increased linearly from 10 to 18"C for every subpopulation germinated at 20-80% gertnination (Fig. 2, Table 1); thus the relationship between tetnperature and the gertnination rate of eaeh subpopulation could be characterized by a required 'thermal time', whieh is the reeiprocal of the slope of the regression line and a base temperature, the temperature-axis intercept of the line.…”

“…Although both the required thermal titne and the base temperature varied among the subpopulations, the linear relationships for the 20-60% subpopulation with higher r^ were eharacterized by relatively constant base temperatures. The distribution of the required thermal time within the seed population eould be approxitnated by the same distribution function as used for the seeds of A, patulus Bertol, in the sub-optitnal range (Washitani & Takenaka, 1984a): where the paratneter m is the median of the distribution, i.e. the required thermal time for the seeds germinating at a germination percentage of 50%, and the spread of the distribution pattern is characterized by the shape parameter A (Fig, 3).…”

Seed germination responses of Monochoria korsakowii Regel et Maack, a threatened paddy weed, to temperature and soil moisture

“…To analyze the temperature-dependency of the rate of germination and its spread among the seeds, subpopulations were identified and characterized by cumulative percentages of 10-80% (Garcia-Huidobro et al . 1982;Washitani & Takenaka 1984). Germination rate was plotted against temperature in the suboptimal range for the subpopulations with cumulative percentages of 10-80%.…”

Germination Responses of Cañahua (Chenopodium pallidicaule Aellen) to Temperature and Sowing Depth: A Crop Growing Under Extreme Conditions

“…Cold temperatures reduce germination percentage of the related herbaceous species Amaranthus patulus Bertol. (Washitani and Takenaka 1984). In experiment 1, 98% of the seeds of the cultivar Warikunca germinated at 3°C (Fig.…”