Comparative analysis of growth and photosynthetic characteristics of (Populus simonii × P. nigra) × (P. nigra × P. simonii) hybrid clones of different ploidides.

To evaluate differences among poplar clones of various ploidies, 12 hybrid poplar clones (P. simonii × P. nigra) × (P. nigra × P. simonii) with different ploidies were used to study phenotypic variation in growth traits and photosynthetic characteristics. Analysis of variance showed remarkable differences for each of the investigated traits among these clones (P < 0.01). Coefficients of phenotypic variation (PCV) ranged from 2.38% to 56.71%, and repeatability ranged from 0.656 to 0.987. The Pn (photosynthetic rate) photosynthetic photon flux density (PPFD) curves of the 12 clones were S-shaped, but the Pn-ambient CO2 (Ca) curves were shaped like an inverted "V". The stomatal conductance (Gs)-PPFD and transpiration rate (Tr)-PPFD curves had an upward tendency; however, with increasing PFFD, the intercellular CO2 concentration (Ci)-PPFD curves had a downward tendency in all of the clones. The Pn-PPFD and Pn-Ca curves followed the pattern of a quadratic equation. The average light saturation point and light compensation point of the triploid clones were the highest and lowest, respectively, among the three types of clones. For Pn-Ca curves, diploid clones had a higher average CO2 saturation point and average CO2 compensation point compared with triploid and tetraploid clones. Correlation analyses indicated that all investigated traits were strongly correlated with each other. In future studies, molecular methods should be used to analyze poplar clones of different ploidies to improve our understanding of the growth and development mechanisms of polyploidy

Pair-wise correlation coefficients of different traits.

<p>**Correlation is significant at the 0.01 level (2-tailed).</p><p>Pair-wise correlation coefficients of different traits.</p

Pn-Ca simulated curve of clone sn3.8 (left) and sn2.3 (right). Solid lines are the simulated curves and white circles are the observed data.

<p>Pn-Ca simulated curve of clone sn3.8 (left) and sn2.3 (right). Solid lines are the simulated curves and white circles are the observed data.</p

Ci-Par curves of poplar clones of different ploidies.

<p>Ci-Par curves of poplar clones of different ploidies.</p

Pn-PPFD curves of poplar clones of different ploidies.

<p>Different ploidy clones are shown by different line types and identification. Triploids are shown by solid lines, diploid and tetraploid are shown as different types of dotted and dashed lines.</p

Clone sn3.8 (left) and sn2.3 (right) Pn-PPFD simulated curve (solid lines are simulated curves and white circles are the observed data).

<p>Clone sn3.8 (left) and sn2.3 (right) Pn-PPFD simulated curve (solid lines are simulated curves and white circles are the observed data).</p

DNA content of sn2.1 (a: the main peak at channel 100), sn3.8 (b: the main peak at channel 150) and sn4.1 (c: the main peak at channel 200).

<p>The ordinate (count) represents the relative value of the cell population, the abscissa (FL1) represents the passageway value of fluorescence. The abscissa location which peak point corresponding were the ploidy of test sample.</p