Figure 2.

Photograph of transgenic poplar plantation (A), and the regulation of tree growth by LSD1, EDS1 and PAD4 (B). Percentage changes in growth parameters are presented in relation to wild-type trees (T89). Lower expression of LSD1 and PAD4, but not EDS1, increased biomass accumulation, measured as stem length and diameter, stem dry weight and xylem accumulation. Higher cell numbers and improved diameters were observed in young parts of the stems of PAD4-RNAi trees, while LSD1-RNAi trees also displayed a higher diameter of the older part of the stem, accompanied by higher stem length. Fluorescent microscopy of stem cross-sections demonstrate: Pi = pith, X = xylem; Δ = cambium, P = phloem. Based on these results the following model was suggested: PAD4 deregulates (inhibits) periclinal cell division. LSD1 has a significant effect upon both periclinal and anticlinal divisions, on cell elongation and differentiation, while EDS1 is a positive regulator of cell division and differentiation in poplars [38,48].