The effect of water stress on the temperature range for germination ofOrobanche aegyptiacaseeds

Abstract

Link to this article: http://journals.cambridge.org/abstract_S0960258500000131How to cite this article: Ermias Kebreab and Alistair J. Murdoch (2000). The effect of water stress on the temperature range for germination of AbstractNon-dormant seeds of Orobanche aegyptiaca were incubated at water potentials of 0 to -1.33 MPa and at constant temperatures from 5 to 29°C. Effects of water potential and temperature on final germination were modelled. In general, germination increased with increased temperature from 5 to 20°C and decreased above 26°C. Maximum germination occurred at 20-26°C and 0 MPa. Germination was reduced as the water potential decreased. Water potential also affected the temperature range over which high germination was observed; at 0 MPa high germination occurred over 9°( 17-26°C) compared with 3°at Ϫ1.25 MPa (17-20°C). The optimum germination temperature also tended to decrease with a decrease in water potential. Final germination could be accounted for by seed-to-seed variation in the population assuming that each seed had a minimum temperature for germination and a maximum temperature above which it would not germinate. Seed-toseed variation in these characteristics was assumed to be normally distributed, and it was further assumed that the two characteristics were independent. Effects of water potential on these temperature requirements were quantified, and the resulting empirical model accounted for final germination with reasonable accuracy (R 2 = 0.96).

Metodologia Para Análise Da Dependência Térmica Da Germinação Pelo Modelo De Graus-Dia

“…Entretanto, podem existir casos em que T b varia dentro de um lote de sementes (Kebreab & Murdoch 2000), principalmente se essas apresentarem dormência. Nesses casos, adaptações são feitas ao modelo para se descrever o progresso da germinação (Kruk & Benech-Arnold 1998, Batlla & Benech-Arnold 2003, mas isso não será tratado no presente artigo.…”

Hydrothermal time analysis of seed dormancy in true (botanical) potato seeds

“…The C b (g) value varies among seeds in the population (generally, but not necessarily, in a normal distribution), while T b is assumed here to be the same for all seeds, which is not always the case (e.g. Kebreab and Murdoch, 2000;Batlla and Benech-Arnold, 2003;Steadman and Pritchard, 2004). u HT is a constant for all seeds in the population, so as C approaches the threshold value for a specific seed fraction [C b (g)], or T approaches T b , the time to completion of germination (t g ) increases proportionately.…”

Temperatura cardeal e potencial hídrico na germinação de sementes de corda-de-viola (Ipomoea triloba)

“…Variações nas temperaturas em estudo mostraram resposta diferenciada à condição de estresse hídrico imposta pelo PEG 8000. Variações similares também foram observadas por Roman et al (2000) e por Kebreab & Murdoch (2000). Entre as diferentes temperaturas testadas, o melhor potencial hídrico foi da testemunha (0), ao passo que os piores potenciais foram os de -0,6 e -0,9 MPa.…”