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Soil moisture conditions affect the sensitivity of Bromus catharticus dormant seeds to light and the emergence pattern of seedlings

Published online by Cambridge University Press:  01 June 2009

Federico P.O. Mollard  and
Pedro Insausti
Federico P.O. Mollard*
Affiliation:
IFEVA-CONICET, Facultad de Agronomía, UBA, Av. San Martín 4453, C1417DSEBuenos Aires, Argentina
Pedro Insausti
Affiliation:
IFEVA-CONICET, Facultad de Agronomía, UBA, Av. San Martín 4453, C1417DSEBuenos Aires, Argentina
*
*Correspondence Fax: +54 11 4514-8730 Email: fmollard@ifeva.edu.ar
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Abstract

The soil moisture regime may affect dormancy of seeds and their sensitivity to signals that promote germination. We studied the effect of moisture regime on the sensitivity to light of dormant Bromus catharticus seeds, and on the emergence pattern of seedlings. Seeds were incubated under continuously hydrated, continuously dehydrated, or fluctuating moisture regimes in a controlled environment (25°C, darkness) for 2 months. After moisture treatments, seeds were exposed to red or far-red light pulses, or to darkness, to determine germinability. In addition, grassland mesocosms with intact seed bank and vegetation were irrigated or subjected to a drought regime in a glasshouse at summer temperatures. After 2 months, the temperature was reduced to correspond to grassland temperatures in autumn; the canopy was removed and half of the mesocosms were covered with filters that exclude red light. Density of B. catharticus seedlings was evaluated after 2 weeks. Dormancy decreased in continuously hydrated seeds but they still required red light for germination. In contrast, an important fraction of seeds that experienced continuously dehydrated or fluctuating moisture regimes germinated in darkness or after far-red light pulses. In the mesocosms that had experienced a soil drought, a higher density of seedlings emerged in the absence of red light than in the daily irrigated mesocosms. This indicates that a fraction of B. catharticus seeds acquired the capability to germinate under the canopy, especially in the drought moisture regime. Results indicate that the soil moisture environment experienced during dormancy affects the sensitivity to light of B. catharticus seeds, as well as the emergence pattern of seedlings.

Keywords

Bromus catharticusgerminationgrasslandslightred:far-red ratioseed dormancysoil water availability
Type
Research Article
Information
Seed Science Research , Volume 19 , Issue 2 , June 2009 , pp. 81 - 89
Copyright
Copyright © Cambridge University Press 2009

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