PHYSIOLOGICAL ACTION OF THE GERMINATION INHIBITOR IN THE HUSK OF <i>AEGILOPS KOTSCHYI</i> BOISS

Wurzburger, Judith; Leshem, Y.

doi:10.1111/j.1469-8137.1969.tb06445.x

Cited by 39 publications

(23 citation statements)

References 11 publications

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“…On the other hand, improvement in germination through removal of the bract, glume or husk has been observed in other grasses (Fandrich and Mallory-Smith 2006;Wurzburger and Leshem 1969). We also observed an increase in both germination and synchrony for dehusked seeds (Fig.…”

Section: Discussionsupporting

confidence: 62%

Factors and mechanisms influencing seed germination in a wetland plant sawgrass

2008

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Sawgrass (Cladium jamaicense) is the predominant plant and vegetation community in the Florida Everglades. Germination of sawgrass seeds in the laboratory or nursery has been difficult and problematic, yet little is known about the physiological mechanistic regulation of the sawgrass seed germination process. In the present study, we examined the factors and mechanisms that influence sawgrass seed germination. We found that removal of seed husk and bracts, pre-soaking with bleach (hypochlorite), breaking the seed coat, or combinations of these treatments promoted the rate and success of germination, whereas presence of seedencasing structures or treatment with husk/bract extract inhibited germination. We further detected the presence of abscisic acid (ABA) in the husk and bract. Experiments with ABA and gibberellin biosynthesis inhibitors fluridone and tetcyclacis suggested that ABA already presented in the pre-imbibed seeds, and not derived through post-dormancy de novo synthesis, contributed to the inhibition of seed germination. Examination of bleach and mechanical treatments indicated the physical barrier presented by the seed-encasing structures provided additional mechanism for the long-term delay of seed germination. Based on the results of this study and others, we discussed the implications of sawgrass seed dormancy and germination in relation to its natural habitat and proposed a hypothesis that the protracted seed dormancy in sawgrass offered an adaptive advantage in the pre-anthropogenic Everglades environment, but may become a liability in the current man-managed Everglades water system.

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Section: Discussionsupporting

confidence: 62%

Factors and mechanisms influencing seed germination in a wetland plant sawgrass

2008

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“…A priori, allelopathic effects seem unlikely, because these are usually thought to be highly specific, but we observed germination inhibition in most species in each source community (D. E. Goldberg et al, unpublished data ), and the magnitude is highly consistent between source communities and years. On the other hand, germination inhibition from surficial chemicals on seed hulls is known from two grass genera that occur in our communities: Avena (Naylor and Christie 1956) and Aegilops (Wurzburger and Leshem 1969; ), providing some support for this mechanism, at least intraspecifically (Evenari 1949). Ongoing experiments are investigating the phenomenon.…”

Section: Discussionmentioning

confidence: 87%

Density Dependence in an Annual Plant Community: Variation Among Life History Stages

Goldberg

Turkington

Olsvig‐Whittaker

et al. 2001

Ecological Monographs

165

185

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Most studies of density‐dependent demography in plants consider the density only of the single focal species being studied. However, density‐dependent regulation in plants may frequently occur at the level of the entire community, rather than only within particular species. In addition, because density dependence may differ considerably (even in direction) among demographic parameters, generalizing about patterns of density dependence and extrapolating to lifetime fitness and to population dynamics require comparisons among life history stages, as well as among types of species and physical environments. We constructed seminatural communities of desert annuals composed of all the constituent species in the same relative proportions as found in the natural habitat. These experimental communities were planted at a range of densities that extended far above and below mean natural field density. We compared among physical environments (irrigation treatments), among communities from different physical environments, and among growth forms (dicot and graminoid) to search for generalizations about the magnitude and direction of density dependence. Strong evidence of community‐level density dependence was detected at all three life history stages studied in these desert annuals: emergence, survival, and final size. However, both the direction and degree of consistency of this density dependence varied considerably among the stages. The strongest and most consistent competitive effects were experienced at the emergence stage, where the mechanism is most likely a form of interference competition rather than exploitation competition. At the survival stage, the magnitude of effects was highly variable among physical environments and source communities, but negative effects were relatively rare, with either positive or no significant effects of increasing density. Thus, exploitation competition was also unimportant at the survival stage. In contrast, for growth, exploitation competition appeared to be the primary mechanism of interaction influencing growth. This variation in mechanism, direction, and magnitude of interactions among life history stages suggests that current models of plant community structure that are based largely on exploitation competition as it influences growth (with mortality a simple function of growth) are inadequate for even this simple annual plant community. We also compared growth forms and found that graminoids were superior competitors to dicots at the emergence and survival stages; they also had higher emergence and survival, regardless of density. Consistent with this result, grasses are always the numerical dominants in the source communities. In contrast, the two growth forms did not differ in competitive ability for growth, and dicots were consistently larger individuals, independent of density, even though grasses were also usually the biomass dominants in the source communities. These results suggest the importance of nontrophic mechanisms of interaction in controlling community structure an...

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“…Total neighbour seed biomass was not correlated with the mean time to N. pulchra emergence at either density nor overall. In contrast, germination experiments with species of Aegilops have shown very clear evidence of self‐inhibition via hormones on the surface of the spikelets (Wurzburger & Leshem 1969; Lavie et al . 1974).…”

Section: Discussionmentioning

confidence: 99%

Accelerated seedling emergence in interspecific competitive neighbourhoods

2000

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Seed dormancy models suggest that evaluation of environmental conditions should influence the decision to germinate and that waiting for more favourable conditions may increase potential fitness. However, because rapid emergence is often positively correlated with performance and survival, an alternative strategy to accelerate the rate of emergence may increase the potential for site pre-emption. This response is more likely to be found in seasonal environments with greater potential for rapid resource depletion in which early emergence may confer a competitive advantage. The experiments reported here found more rapid emergence in a perennial grass species when it was planted in potentially highly competitive interspecific neighbourhoods. This response suggests an inherent ability in seeds of this species to sense and respond to the competitive nature of the immediate neighbourhood.

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PHYSIOLOGICAL ACTION OF THE GERMINATION INHIBITOR IN THE HUSK OF AEGILOPS KOTSCHYI BOISS

Abstract: SUMMARYThe germination inhibitor contained in the glume and hull of Aegilops kotschyi, an IranoTuranian graminaceous species growing in Israel, was investigated. It appears to function via the gibberellin (GA) metabolism of the plant and is coumarin-or abscisin-like in action.

Cited by 39 publications

References 11 publications

Factors and mechanisms influencing seed germination in a wetland plant sawgrass

Factors and mechanisms influencing seed germination in a wetland plant sawgrass

Density Dependence in an Annual Plant Community: Variation Among Life History Stages

Accelerated seedling emergence in interspecific competitive neighbourhoods

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