THE EVOLUTIONARY TRENDS IN THE CHANGES OF PHOTOSYNTHETIC
APPARATUS IN GENUS TRITICUM L.
Khramtsova E.V., Kiselyova I.S.
The Ural State University named after A.M.Gorky, Ekaterinburg, Russia
The speciation in the genus Triticum L. is immediately related to alloploidy due to the
spontaneous hybridization of 14-chromosome species of Triticum L. (T. beoticum и T. urartu,
the ancestors of subgenome Ab и Au, relatively) and Aegilops and their subsequent evolution.
During the evolution the significant structural-functional differences in photosynthetic
apparatus of ancient and modern wheat species have occurred. The objective of this study was
to investigate the evolutionary trends in the changes of photosynthetic apparatus in genus
Triticum L.
In evolution of genus Triticum L. the increase of plant productivity was marked
against the decrease of photosynthetic rate per unit leaf area (the so called “paradox of
Evans”). One of its reasons is the genetic changes in photosynthetic activity of a single
chloroplast caused by adding of Aegilops subgenomes to wheat genome. The other reason is
the changes in interior organization of mezophyll: the decrease of chloroplast number per unit
leaf area and interior assimilation area in leaf. From one hand these changes were caused by
the intensification of plant growth and the formation of a larger leaf area according to nuclear
ploidy, that gives more advantages to modern alloploid forms compared to ancient diploid
species. From the other hand they have led to the decrease of photosynthetic rate per unit leaf
area in polyploids due to the worse conditions for СО2 diffusion to carboxylation centers in
leaf. The study of the structural-functional leaf organization in plants with different genomes
have shown the non-sufficient approach in analyses of alloploids from the position of
polyploidy as the diverse origin of the genome strongly imprint the formation of
photosynthetic parameters. The changes in leaf photosynthetic apparatus of alloploid species
were often the same, as in autopolyploids. Mainly it relates to groups of species that
originated from one ancestral form. In the majority of cases genome constitution influenced
on the structure of photosynthetic apparatus and its functional characters.