The influence of urban surrounding on the integument and the water content in the needles of the species of the family Pinaceae Lindl

Changes of the water regime (the quantities of free and bound water and the concentration of the cellular fluid) and those of the integument of four species of conifers of the family Pinaceae Lindl. (Archangel fir – Pinus sylvestris L., Siberian cedar – Pinus sibirica L., Siberian spruce – Picea obovata Ledeb., Siberian fir – Abies sibirica Ledeb) in the polluted areas of the town of Gorno-Altaisk (Republic Altai) were shown. Partial decomposition of the elements of the integument of the needles was found. Thus, toxic substances may affect the thickness of the cuticle, either making it decrease (as is the case with Siberian cedar and the fir), or increase (the spruce), or it remains as thick as that of the control set (Archangel fir). The cuticle of the fir is thinner by 1.12 μm, the other parameters differing very little from those of the control set. The cuticle of the fir increases under urban conditions 1.43 times. Both types of the pine demonstrate a greater variety of the structure parameters. It is worth noting that the thickening of the cuticle of the fir does not increase the protection from the toxins of the urban surrounding. Though the cuticle becomes thicker, it often becomes undulate, flexuous, parted, and even broken interrupted, which makes it easier for toxic agents to penetrate into the inner tissues of the needle. As it is known, the cuticle, while being a protective layer, is still quite penetrable for some substances, including gases and water. Changes of free and bound water ratios are found, i.e. those towards the increase of the proportions of more ordered forms, which, in its turn, results in the decrease in the runout under the influence of adverse factors of the surrounding. The concentration of the cellular fluid varies, depending on the season and the levels of pollution. All those changes are closely related to the resistant qualities of plants. The most resistant to the gas pollution of Gorno-Altaisk are the Siberian cedar (Pinus sibirica) and the Archangelfir (P. sylvestris), while the Siberian spruce (Picea obovata) and the Siberian fir (Abies sibirica) turn out to be the least resistant species.

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