RESUMEN

Aerial seed banks facilitate population persistence by extending the temporal range of seed dispersal. Knowing the temporal range of germination will improve our understanding of the relationship between seed germination dynamics and aerial seed bank storage duration. We tested the effects of temperature (12/12 h of 5/10, 10/20, 20/30 and 25/35 °C) and light variation (12 h light/12 h darkness and 24 h darkness per day) on germination of Rumex obtusifolius L. seeds retained in an aerial seed bank for 0, 2, 4, 6, 8 and 10 months. Freshly harvested R. obtusifolius were non-dormant and exhibited germination rates of up to 92%. Overall, seeds of R. obtusifolius germinated reliably at all but the lowest temperature (5/10 °C). Seeds maintained high viability throughout the collection period, indicating that fluctuating weather conditions had little influence on seed germination. Thus, the species can maintain viable seeds in aerial storage for up to 10 months and contribute viable seeds to the soil seed bank year-round. This ability to maintain a renewed soil seed bank contributes to the species' strong resilience in colonizing disturbed areas and makes it a difficult weed to control.

RESUMEN

The high-throughput analysis of respiratory activity has become an important component of many biological investigations. Here, a technological platform, denoted the "MultiSense tool," is described. The tool enables the parallel monitoring of respiration in 100 samples over an extended time period, by dynamically tracking the concentrations of oxygen (O2) and/or carbon dioxide (CO2) and/or pH within an airtight vial. Its flexible design supports the quantification of respiration based on either oxygen consumption or carbon dioxide release, thereby allowing for the determination of the physiologically significant respiratory quotient (the ratio between the quantities of CO2 released and the O2 consumed). It requires an LED light source to be mounted above the sample, together with a CCD camera system, adjusted to enable the capture of analyte-specific wavelengths, and fluorescent sensor spots inserted into the sample vial. Here, a demonstration is given of the use of the MultiSense tool to quantify respiration in imbibing plant seeds, for which an appropriate step-by-step protocol is provided. The technology can be easily adapted for a wide range of applications, including the monitoring of gas exchange in any kind of liquid culture system (algae, embryo and tissue culture, cell suspensions, microbial cultures).

Asunto(s)

Brassica napus/metabolismo , Ensayos Analíticos de Alto Rendimiento/métodos , Brassica napus/crecimiento & desarrollo , Calibración , Respiración de la Célula , Fluorescencia , Germinación , Concentración de Iones de Hidrógeno , Oxígeno/metabolismo , Estándares de Referencia , Semillas/crecimiento & desarrollo

RESUMEN

• Here the relationship was investigated between metabolic activity, state of hydration and seed viability in the desiccation-intolerant (recalcitrant) seeds of Idiospermum australiense, a rare and primitive angiosperm tree restricted to wet tropical forest. • Seed CO2 evolution rate, R, was monitored in fully hydrated (control) seeds and seeds that were allowed to desiccate under ambient conditions over a period of c. 90 d. • During desiccation R increased dramatically toward a peak at a seed relative water content of 39 ± 3% (relative to maximum water content, which corresponded to 0.45 ± 0.03 g water g-1 d. wt) followed by a decline toward zero with total desiccation. This peak constituted a 10-fold increase in mean R, relative to the control. Exposing seeds to O2 -free air at this peak induced a further large, but transient, increase in CO2 evolution, indicating that the peak developed in the presence of oxidative phosphorylation, rather than due to the absence of it. • The magnitude and mode of the observed increase in CO2 evolution in response to desiccation is unlike any reported so far and thus adds new information about metabolic changes that may occur as the water content of desiccation-intolerant seeds declines.

RESUMEN

We examine the relationship of seed oxygen consumption rate (V̇o2 ) to seed moisture content, seed mass, and seed age in 22 ecologically diverse tropical species. These seeds vary greatly in moisture content, age, mass, mechanism of dormancy and length of viability. We quantify each relationship with a power equation, V̇o2 =aXb , where X is the independent variable. Seed moisture content (MC) explains 80% of the variation in mass-specific V̇O2 (ml O2 g-1 h-1 ) among seeds of all species, whereas seed mass explains < 1%. However, when seeds are reclassified as moist (> 28% MC) or dry (≤ 28% MC), seed mass explains 54% of the variation in mass-specific V̇o2 (ml O2 g-1 h-1 ) within dry seeds, but no significant variation within moist seeds. In dry seeds, seed age explains only 27% of the variance in mass-specific Vo2 , although seed age and moisture content are negatively correlated. On a per seed basis, seed mass explains 54% of the variation in mass-specific V̇o2 (ml O2 h-1 per seed) in dry seeds and 83 % of the variation in moist seeds: the exponents of the power function, 0.54 in dry seeds and 0.78 in moist seeds, are within the range reported for the allometric relationship of oxygen consumption and body size in animals and prokaryotes. We present a framework for future studies that recognizes seed respiration as an important, yet unstudied, component of tropical seed ecophysiology. We discuss the ecological significance of seed respiration in three groups of tropical species which differ in seed moisture content, mass, viability, and post-dispersal moisture regimes: (1) shade-intolerant pioneer species with small, dry, orthodox seeds; (2) seasonally dormant species; and (3) shade-tolerant primary forest species with large, moist recalcitrant seeds.