Abstract
Centaurea glomerata Vahl is an annual, monoecious and herbaceous member of Asteraceae, found in some localities of different topographic features/habitat conditions along the Mediterranean coastal region of Egypt. This study aimed to investigate some environmental gradients including edaphic and climate criteria on morphological, reproductive traits as well as phenolic and flavonoid metabolites in this species. Three distinct populations were selected. Two of them were located in coastal sand dunes (found in Rosetta region in Egypt); one was located on flat sand dunes, whereas the other grown on sloping ones. Meanwhile, the third population was represented in the rocky hillside of Burg El Arab region. The population detected in the sloping sand dunes showed best morphological and reproductive features, whilst the opposite was true for that represented on the rocky hillside. Moreover, the free phenolic and flavonoid compounds prevailed in the later. The meteorological data revealed that the rocky hillside received relatively lower minimum temperature and higher solar irradiance, while the sand dunes of Rosetta showed more warmer conditions. Light intensity and wind speed were reduced on the sloping sand dunes. The Canonical Correspondence Analysis (CCA) exhibited a clear correlation between most of metabolites detected and the population found on the rocky hillside along with higher solar irradiance prevails. The morpho-reproductive traits were related to climatic gradients and some soil criteria. These results revealed that the changes in micro-topography, that may lead to change in soil and climate variables, is the most important environmental gradient that controls the morphological and biochemical features of C. glomerata. Solar irradiance and/or light intensity are key factors playing a role influencing the measured traits of this species. These findings suggest that accumulation of secondary metabolites could be a biochemical strategy and an adaptational criterion for such species under stress conditions.
Highlights
The ecological environments surrounding plant species are mostly heterogeneous, creating ecological variables that influence plant development along the prevailing environmental gradients (Bazzaz, 1996)
These criteria were more pronounced in individuals found on the flat sand dunes of Rosetta in comparison with those found on the rocky hillside
In terms of dry weights of heads in addition to seed numbers and mean seed mass per plant, the plant samples collected from the rocky hillside of Burg El Arab attained lower values compared with those located in both microsites of Rosetta (Table 2)
Summary
The ecological environments surrounding plant species are mostly heterogeneous, creating ecological variables that influence plant development along the prevailing environmental gradients (Bazzaz, 1996). The change in microtopography associated with varying edaphic and climatic factors may impose populations of some species to develop locally adaptable functional traits (Hegazy, 2001; Lobo et al, 2003). Several studies have revealed the significance of morphological, biochemical and reproductive traits to identify and interpret plant responses to environmental heterogeneity (Dujardin et al, 2011; Kahmen and Poschlod, 2008; Roux et al, 2017). Other plant species found in different habitats and/or microhabitats have not been explored yet, and studies are still lacking, under arid and semi-arid conditions where water economy amongst populations is a more influential factor. The common adaptations of some traits with respect to morphology, reproduction and biochemical activities of plant populations may be more obvious under these circumstances. It will be interesting to study additional missing plants and, fill this gap
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