Synthetic autotetraploid plants of Phlox drummondii exhibit significantly higher photosynthetic rate at C11 generation than teh diploid progenitor

Abstract

Multiplication of genome has significant roles in the adaptation and evolution of plants and is accompanied by various physiological changes. Synthetic autotetraploids and its diploid progenitor in Phlox drummondii (Polemoniaceae) have given us a unique opportunity to effectively study the effect of gene dosage on biochemical and physiological activities of the plants. The entire genome was doubled by colchicine and now the synthetic autotetraploids are running into 11th generation (C11). They are not only morphologically healthier than their diploid progenitor but are also photosynthetically more efficient on leaf area basis. Moreover, using different generations of tetraploid plants, we are able to study whether the better growth and physiological performance is the result of only genome duplication or the product of genome dosage combined with gradual environmental adaptation over the years. The increase in leaf dry weight is 55% and 80% in C0 and C11 generations, respectively. The increase in chlorophyll content is about 18% in C0 generation while it is 110% in C11 generation over the diploid progenitors. The light saturation point of tetraploids of both the generations is much higher. The stomatal conductance is only little higher at C0 generation while it has increased 2.75 times in C11 generation. Net photosynthetic assimilation is increased by about 43% in C0 generation (12 µmol CO2 m-2s-1) and more than doubled in C11 generation (17 µmol CO2 m-2s-1). We intend to present the anatomical details, quantification of enzymes, DNA and chlorophyll per cell and, assess the response of photosynthesis to CO2 concentration on per cell and per unit DNA basis and discuss its theoretical and practical implications.