Morphometric variations as acclimation mechanisms in Zostera noltii beds (original) (raw)
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Helgoland Marine Research, 2000
The morphological and physiological differences between two morphotypes of Z. noltii Hornem. were studied in the intertidal meadows on the south-western Iberian Peninsula (Palmones river estuary and Ria Formosa). A small-leaved morphotype (SM) grows mainly at high intertidal sites, meadow edges or in recently deposited sandbanks, whereas a large-leaved morphotype (LM) generally thrives in well-structured beds or in deeper places. This study deals with the morphological, biochemical and physiological differences between these morphotypes as well as the ecological implications of the occurrence of different morphotypes in the same meadow. Shoot length, leaf width, rhizome internode length, roots per node, root length, leaf nutrient and pigment contents, and photosynthetic rates of both morphotypes were compared. The below-ground architecture (root and rhizome complex) of both morphotypes was more developed in sites characterized by higher hydrodynamics and/or a lower nitrogen content in sediments. Both morphotypes showed similar values for photosynthetic efficiency, dark respiration rate and compensation irradiance. On the other hand, the net photosynthetic capacity was much greater (5-fold) for the SM. This difference could explain the greater growth rate and faster leaf turnover rate of the SM compared with the LM. The occurrence of the SM in newly settled areas (and in the meadow edges) could be explained on the basis of its higher growth rate, which would allow a faster spreading of the meadow and/or better recovery after burial resulting from stormy weathers.
Biological Journal of The Linnean Society, 2002
Plants from four populations of Hordeum spontaneum originating in distinct environments of Israel were compared for stress induced phenotypic plasticity. The environments ranged along a gradient of increasing rainfall amount and predictability from low (desert) to moderate (semi-steppe batha) to high (Mediterranean grassland and mountain, the latter also experiencing frost stress). The plants were exposed to a set of four treatments: no stress (optimum water and nutrients), water, nutrient and both water and nutrient stress. Plants from the four populations (or ecotypes) exhibited different patterns of plasticity in response to the different stresses (water and nutrients) and in different trait categories (reproductive, fitness and resource allocation). The importance of plasticity in response to water stress appears to decrease, and to nutrient stress appears to increase along the increasing rainfall gradient. The mountain ecotype, growing in an area with high potential productivity (amount of rainfall) but experiencing periodic frosts, was the most plastic among ecotypes in resource allocation under both water and nutrient stress, but exhibited low plasticity in other trait categories. In contrast, the desert ecotype had low plasticity in resource allocation under water stress and the lowest plasticity among the 4 ecotypes in all trait categories in response to nutrient stress. The ecotype originating in Mediterranean grassland, a predictable and most favorable environment, was highly plastic in fitness and allocation traits in response to low nutrient levels which is likely to occur due to competition in productive environment. We discuss the observed differences in ecotype plasticity as part of their environmentally induced adaptive 'strategies'. We found no support for the hypothesis that plants originating in environments with greater variation and unpredictability are more plastic.
Scientific reports, 2017
The present study aims to assess the plastic response of Zostera noltei meadows traits under spatio-temporal shifts in salinity combined with sediment environmental variables (temperature; pH; loss-on-ignition (LOI); carbon (C) and nitrogen (N) pools (top 5 cm)). Z. noltei biomass, C and N pools, leaf photosynthetic performance and esterified fatty acid (FA) profile were assessed within a temperate coastal lagoon during winter and late spring, along sites spatially distributed. None of the surveyed traits for Z. noltei displayed a clear spatial trend. Z. noltei proved to be euryhaline, whose biology was only slightly affected within this salinity range, in each season (14-39 in winter; 33-41 in late spring). Seasonal differences in salinity and environmental parameters explain the differences recorded in Z. noltei traits (aboveground biomass, N and C pools; photosynthetic performance). Spatio-temporal salinity shifts did not significantly affect the pool of FA present in Z. noltei. ...
Hydrobiologia, 1993
Apparent photosynthetic rates (APS) of two Zostera noltii Hornem. morphotypes were measured in air and in water at different temperatures with a closed infra-red gas analysis system (IRGA). Hyperbolic functions accurately described the photosynthesis-CO2 relationships when the leaves were exposed to air. The photosynthetic behaviour in water, on the contrary, could not be described by Michaelis type kinetics, due to the existence of a rapid transition from the initial slope to the saturation phase. Both morphotypes (narrow-leaved, NLM and large-leaved, LLM) showed higher APS rates in water than in air, although the highest APS rates, in air as well in water, were recorded for the NLM. Temperature had a significant influence on the photosynthetic parameters: APSmax (maximum photosynthetic rate) decreased (in air and in water) with increased temperature in both morphytypes; compensation points (CP) in air increased at high temperature, especially in the LLM. NLM specimens showed enhanced affinity (lower Km) with increasing temperature in air. On the contrary, Km values in water were not significantly affected by temperature. The results suggest that NLM specimens are better adapted than the LLM to occur exposed to air. The distributional pattern of the two morphotypes in the Palmones Estuary is discussed on the basis of their photosynthetic behaviour.