Germination response of Phalaris paradoxa L. seed to different light qualities

Abstract

The influence of different light regimes on the germination of Australian and English populations of Phalaris paradoxa L. (awned canary-grass) seed was investigated to determine the impact of changing tillage practices on weed infestation. Seeds of all biotypes were highly viable, but differed in levels of innate dormancy (26-99%). In one experiment seed from a single Australian biotype, either enclosed in the spikelet glumes or having the spikelet glumes removed, were exposed to nine light treatments. Germination was stimulated by red and white light, but was inhibited by far-red light. Time to 50% germination was less for seed enclosed in the spikelet glumes than for naked caryopses, although the final percentage of seed germinating when still enclosed in the spikelet glumes was significantly lower than for naked caryopses. In another experiment, six Australian and English biotypes with varying dormancy characteristics were exposed to eight light treatments. Red light did not stimulate germination in the deeply dormant biotype, however stimulated all other biotypes. Germination in darkness was below 20% in all biotypes except for one where germination was 51%. To overcome dormancy seeds were imbibed and placed in darkness at 16°C for either 7 or 14 days prior to exposure to red or white light for a single 15-min period. Dormancy in all biotypes was overcome indicating that a period of burial may decrease the dormancy level and increase seed sensitivity to light. This increased light sensitivity suggests that exposure to light during tillage may stimulate germination in P. paradoxa seed.

Implications of Behavior and Gut Passage for Seed Dispersal Quality: The Case of Black and Gold Howler Monkeys

“…Germination patterns were evaluated following recommendations by Taylor et al (2004) and Vila‐Aiub et al (2005). Randomly selected sub‐groups of 50–60 seeds from each species (sub‐groups numbers for each species in Table 1) were fitted to a sigmoid function, where the parameters a, x 50 and b represent the maximal percentage of germination, time (days) at which 50 percent of seeds had germinated, and slope around x 50 , respectively (Taylor et al 2004, Vila‐Aiub et al 2005). Parameter b provides an indication of the distribution of seed germination over time.…”

“…The experiment was ended after 30 d without new germinations. Germination patterns were evaluated following recommendations by Taylor et al (2004) and Vila-Aiub et al (2005). Randomly selected sub-groups of 50-60 seeds from each species (sub-groups numbers for each species in Table 1) were fitted to a sigmoid function,…”

“…where the parameters a, x 50 and b represent the maximal percentage of germination, time (days) at which 50 percent of seeds had germinated, and slope around x 50 , respectively (Taylor et al 2004, Vila-Aiub et al 2005. Parameter b provides an indication of the distribution of seed germination over time.…”

Burial depth and cultivation influence emergence and persistence of Phalaris paradoxa seed in an Australian sub‐tropical environment

“…The aim of this present study was to determine the influence of reduced tillage systems and seed burial depth on the periodicity of seedling emergence and seed persistence in soil. Brief exposures of buried P. paradoxa seed to light, such as experienced during soil tillage, can greatly increase germination (Taylor et al. , 2004), which could have implications for improved weed control.…”

Luz e KNO3 na germinação de sementes de Ageratum conyzoides L. sob temperaturas constantes e alternadas

“…Sementes de Eupatorium adenophorum apresentaram apenas 17% de germinação no escuro, enquanto na presença de luz, a germinação foi de 93% (Lu et al, 2006). Taylor et al (2004) constataram que em sementes de Phalaris paradoxa a germinação no escuro foi menor do que 20% em todos os biótipos testados exceto em um que apresentou germinação de 51%. Na presença de luz, a germinação foi de 91% a 97% entre os biótipos avaliados, com exceção de um que apresentou 27%.…”