Oggi 21/09/2019 ore 15:38

Adaptations to the environment


Adaptations to the environment

The Etna has two faces, two landscapes that could not be more contrasting. One is the happy "campus aetneus" so praised by the ancients for its extraordinary fecundity.
"The branches are heavy with fruit" (Ovid).
The other is the squalor of "sciara" in the lava deserts of slag, blackened iron lava, sometimes inaccessible for centuries to the vegetation, scorched by the summer sun, places that seem doomed to desolation.
A certain uniformity of the landscape here and there interrupted by scattered clumps of plants, which in periods of full bloom illuminate life on the most monotonous and inhospitable places.
Here we can see one of the many unique aspects of the interactions of the Etna flora, including genetic traits and environmental characteristics.
It is the case of a Composita of the type Senecio, where the conditions of adaptation to changing pedoclimatic factors, leading the species to take over, with the gradual change of altitude, certain phenotypic characteristics of the alpine entities.
Senecio_dell_etnaThe Senecio (Senecio aetnensis jan), glaucous Senecio, below the upper limit of the Etna’s vegetation, in the lower marginal aspects of the Astragaleto Altomonte or in its dilated aspects, presents the leaf surface covered with abundant wax, an entire leaf margin or just pronged, a more pronounced succulence of the epigean parts, a reduction in the number of stomata per unit area and finally a series of physiological mechanisms that give the species a strong resistance to water and heat stress.

This polymorphism of the species is easily evidenced by the biometric studies undertaken to the populations of the Senecio gender found at the highest altitudes (Senecio aetnensis), at the intermediate altitudes and at the lowest altitudes.
Furthermore, with these studies, it is possible to highlight the obvious contribution of environmental factors and their correlation with the expression of certain phenotypic characters, whose plasticity changes due to the diversity of characters and altitudinal distribution against those three distinct and certainly questionable taxonomic entities. Staying on the theme of the interaction between genotype and environment may be interesting to see what happens when you reverse the environmental conditions of Senecio aetnensis, which is losing its taxonomic characters, when the mountain area is gradually brought down until the environment best suited to other populations.

A consequence of the adaptation to the environment of the high parts of Mount Etna is a calcareous grasslands (ability to survive in drought conditions) more or less marked, and a typical morphology of entities, grouped in highly specialized plant associations to the pedoclimatic consequences, and consequent tendency to assume the same posture pulviniforme and somewhat prickly, by reduction and transformation of leaves.
It, thus, creates the conditions most suitable for an efficient resistance to the deficit between availability of water from soil and leaf loss by transpiration.
Other characters such as the impressive development of radical volcanic body aimed at finding a sufficient amount of water from deeper soil layers also, the significant reduction and flattening of the ground portion of the entire air (pulvini vegetation), the metamorphosis of the leaf apparatus is capable of reducing water loss by transpiration, a strict metabolic control is particularly specialized in the photosynthetic cycle and respiration, made of the plants of this particular environment of the Mount Etna an unequal source of data for the study of the adaptations to the environment of the vegetables of dry areas and their productivity in extreme resistance conditions.

Very often, unfortunately, we do not pay attention to a responsible behaviour or attention to a vegetable that just asks to be left on the place that has conquered. We miss humbleness at the time of recognising, due to the more sophisticated technical and scientific progresses, our smallness in front of the marvellous things that are created, day after day, season after season, where the most humble vegetable essences conquer their peculiar environments.
Thanks to this well-concealed ignorance, shall be preferred, because of big economic interests and the influence of certain fashion in the selection of ornamental species, those entities most obvious and striking.
The result of this choice is the tendency in our villas and gardens, to play anonymous and monotonous patterns with lush tropical vegetation, in striking contrast to the examples of local vegetation, which seems insignificant to most, but for which it is known the great potential and the proper naturalistic sense.
Who would think to grow on the slopes of Sciara_con_fioritura_di_camomilla_sull_etnaEtna Bagolaro instead of Araucaria, an oak or an oak instead of a spruce, a broom instead of a Yucca Etna or simply the grassy "lawn" with a plebeian fescue (Festuca circummediterraneaPattzke).
These grasses, somewhat modest, when seen in the distorted perspective of a utilitarian narrow sector, forms in the Etna extending mono specific populations on unstable slopes, windswept and subject to heavy erosion, exerting an irreplaceable colonizing and stabilizing action.

In these environments, certainly not the most hospitable ones, its heads, green for only a few months each year, determine the soil and give to the landscape plant of that altitudinal range, attributable to the portion of a higher altitude with vocation for forestry or to the less altitude of the Astragaleto, that typical aspect that is reflected in similar aspects found in other surveys in the Mediterranean.
Even for Festuca Etna is able to enhance correlations between phenotype and environment, subjecting the species cultivated in irrigated fields appropriately.
Subjected to these experimental conditions, the fescue tend to take a vegetative luxuriance of its assets accompanied by a drastic change in the biological cycle (total absence of flowering), unchanged as a result of soil conditions as well as thermal and photoperiod.

Through this example you can easily guess, once again, the role played by environmental factors, which in the territory under consideration help to regulate the cycle of fescue and contribute to confer, along with other plant species in association to other species of the place, those peculiar characters plant physiognomy to that vegetable group enclosing an absolute perfect harmony and balance in rigorous equilibrium with the features of the surrounding environment.