We are presenting the results of our research on 20 both spontaneous and cultivated woody species (Gymnosperms and Angyosperms) found near several industrial areas in Romania: Borzesti, Bacau county where the pollutants are mainly gaseous (SO2, Cl, NH3) but also solid (coal and soot), Bicaz and Tasca, Neamt county where the pollutants are sedimentable powders of lime and cement. Even if the pollutants that are involved are chemically different from each other, the placing of the three industrial areas in depression areas with atmospheric calm causes the occurance of the strongest atmospheric pollutants – vegetation impacts in the discussed areas.
We mention the following reactions the investigated species had in common responding to the gaseous and solid industrial noxes: - the foliar surfaces’micromorphology alteration caused by the solid pollutant deposits that cause through their adherence inactivate the photosynthetically active parts of the leaves; - the obstruction of the breathing and perspiration of the leaves by obturing the ostiola of the stomata; - the weakening of the tree’s general state; the trees become vulnerable to late spring freezes and pathogenic fungi attack; - episodes of partial or total defoliation: there are plant species whose leaves show signs of sufferance (chloroses, necroses) but there are also species whose leaves don’t manifest visible symptoms but have partial or total defoliation episodes.
Our S.E.M. (Tescan Vega SBH, Faculty of Biology) research show the major role of foreign deposits in defoliation process.The installing on such solid deposits of a pathogen phyllosphere represents an indicator of the early ageing process of the leaves and also a possible cause of the defoliation or even death of the trees.
The identification of the polyphenolic compounds in the leaves of the species that don’t show visible foliar sufferance signs through histo-chemical methods can be considered, according to our research, a true bioindicator that announces future defoliation phenomena.
Regardless of the chemical nature of the atmospheric pollutant, the structural changes of the leaves are almost the same as the epidermis (upper and lower), the mesophyll and the vascular tissues are affected; as a particularity there are changes in the secretory ducts of the needles of the Gymnosperms and in the Caspary endodermis around vascular tissues.
In conclusion, when it comes to chronically aggression from the atmospheric pollutants, regardless of their nature, the responses can be extremely different but very similar at the same time.