On the features of seasonal water storage and heavy metals accumulation in the leaf phytomass of the genus Acer L. plants
Authors: Kavelenova Lyudmila , Prokhorova Nataly , Rozno Svetlana 
Published: March 2022

&lt;p&gt;&lt;br&gt;In the conditions of the temperate continental climate, which extends to the Middle Volga region (Russia), the growing seasons often show more or less prolonged periods of droughts. Seasonal retention of moisture reserves by the leaf mass of trees and shrubs, ensures the functional activity of their photosynthetic organs, contributes to the &amp;#8220;spatial fixation&amp;#8221; of water as an exclusively mobile component of the biosphere.&lt;/p&gt;&lt;p&gt;One of the forest-forming species of the Samara region is Acer platanoides L., whereas A. tataricum L. participates in the undergrowth and shrub thickets formation. These two &amp;#160;species by now &amp;#160;are &amp;#160;suppressed by A. negundo L. introduced from North America, that occupies anthropogenic environs and comes to natural communities. The dendrological collection formed in the Botanical Garden of Samara University includes, among about 1300 taxa totally, 26 taxa of the genus Acer. The multi-year evaluation of the water content of leaves by months &amp;#160;revealed the dependence of the data on the hydrothermal season conditions. &amp;#160;We use data from the &amp;#160;season not associated with high aridity. The aboriginal Acer platanoides and A. tataricum found water content &amp;#160;50...60% with average values of 56.2 and 54.3%, respectively. The species introduced from Western Europe &amp;#160;had water content values above 60% (A. campestre L, A. pseudoplatanus L., A. opalus Mill., A. obtusatum Waldst. ), A. pseudoplatanus was in the lead with average rates of 68%. The f North American species turned out to be functionally heterogeneous. Here, species with increased leaf water content (A. negundo, A. circinatum Pursh, - up to 70%) and with reduced leaf water content (A. saccharinum L., A. glabrum Torr. - less than 60%) are represented. The species from Central Asia showed the lowest level of water content &amp;#160;(A. ginnala Maxim., A. semenovii Regel &amp;#160;- average of 50.9 and 55.8, respectively). Under conditions of favorable moisture supply, the plants showed differences associated with their origin. Under conditions of stress, they actively use adaptive properties that are less involved in conditions of &quot;comfort&quot;.During the onset of drought, A. negundo, reducing the water content of the leaves, demonstrates an attempt to avoid excessive water losses by rolling the leaf blades.&lt;/p&gt;&lt;p&gt;For the most common &amp;#160;A. platanoides, A. tataricum, A. negundo, the accumulation of heavy metals (Cr, V, Co, Ni, Cu, Zn, Pb) in leaves was quantified by characteristic X-ray radiation (PIXE). The Cr content varied from 0.78 to 11.92 ppm, the minimum Cr concentration was found in the leaves of A. negundo, &amp;#160;the maximum &amp;#160;- A. tataricum. The V accumulation &amp;#160;varied from 12.38 to 31.38 ppm, with a minimum &amp;#160;for A. platanoides and a maximum - for A. tataricum. The species-specific metal accumulation was revealed for: &amp;#160;Co (from 0.75 to 2.46 ppm), Ni (2.44-3.06 ppm), Cu (11.84 -24.01 ppm), Zn ( 20.52-39.95 ppm), Pb (0.30-0.63 ppm). The maximum accumulation of these elements was in the leaves of A. negundo, the average level - A. platanoides, and the minimum - A. tataricum. We assume that more active &amp;#160;water accumulation in phytomass also contributes to a more active accumulation of heavy metals.&lt;/p&gt;