Seed germinability and longevity influences regeneration of Acacia gerrardii

Acacia gerrardii is the only native tree species of the Kuwaiti desert ecosystem. However, anthropogenic disturbances and harsh arid climate have contributed towards the disappearance of this keystone species from its habitat. In this study, effects of different seed pretreatments to break dormancy, water entry pathway, and ecology (seasonal timing) of dormancy loss and germination of A. gerrardii were investigated. Effects of mechanical scarification, hot water treatment (30 s, 1, 2, and 5 min), and concentrated acid scarification (10, 20, and 30 min) on germination percentage and rate (time to 50% germination and final germination) were also examined. Pretreatment with mechanical scarification produced the highest germination in the least time and 20 °C, 40% RH with 12 h of light (2370 Lux) were found to provide the best germination environment. Seeds were rapidly aged at 60% RH and 45 or 50 °C to determine longevity, and the results were analyzed using probit analysis. Times taken for viability of A. gerrardii seeds aged at 45 and 50 °C to fall to 50% (p50) were 38.6 and 9.3 days, respectively, and therefore the seeds can be considered to have medium longevity. Experiments to find the water entry pathway in A. gerrardii indicated that the micropyle region was the primary point of water entry into the seed. Seed burial experiments indicated that though seed retention decreased over time, there was no significant decrease in number of viable seeds after 31 weeks. The findings of this study are important to nursery managers, seed banks, and those involved in conservation and restoration activities

Modelling Weed Seedbank Dormancy and Germination

Weeds are usually more vulnerable to control practices at the seedling stage or at early stages of their growth. Therefore, developing models to predict the timing and extent of weed emergence is useful to assist farmers and agronomist to time pre- and post-emergence control practices to increase their efficacy. However, many important weeds forming persistence seedbanks in agricultural fields present dormancy. In those species, the number of established seedlings is strongly related to the dormancy level of the seedbank, and the timing of seedling emergence depends on the seasonal variation in seedbank dormancy level. Therefore, if we pretend to predict timing and extent of seedling emergence, we should include the regulation of the seedbank dormancy level in our predictive models. In this chapter, we present a conceptual framework to understand how dormancy and germination of weed seedbanks are regulated by the environment. This framework is based on the distinction between those factors that regulate seasonal changes in the seedbank dormancy level (i.e. temperature in interaction with seed moisture content) and those factors that terminate dormancy (i.e. light and alternating temperatures). Changes in the seedbank dormancy level are related to changes in the range of environmental conditions permissive for seed germination, as, for example, the thermal range permissive for germination which is defined by the lower and the higher limit temperatures. Seeds germinate when environmental conditions are within the permissive range, for example, seeds begging to accumulate thermal time towards germination once soil temperature overlaps the permissive thermal range. We present examples of how these concepts can be used to establish functional relationships between dormancy and germination regulating factors (i.e. temperature) and changes in seedbank population dormancy level and germination dynamics in order to develop mechanistic models to predict the timing and extent of weed seedling emergence in the field.Fil: Batlla, Diego. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura. Universidad de Buenos Aires. Facultad de Agronomía. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura; ArgentinaFil: Malavert Pineda, Cristian Jonatan. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura. Universidad de Buenos Aires. Facultad de Agronomía. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura; ArgentinaFil: Fernández, Rocío Belén. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura. Universidad de Buenos Aires. Facultad de Agronomía. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura; ArgentinaFil: Benech-Arnold, Roberto Luis. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura. Universidad de Buenos Aires. Facultad de Agronomía. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura; Argentin