Photosynthetic and growth characteristics of flue-cured tobacco seedlings in well-cellar style transplanting
The well-cellar style transplanting (WCST), widespread in China, was an original transplanting method of flue-cured tobacco, and had obvious advantages when compared to conventional transplanting (CT). WCST accelerated the growth of tobacco seedlings; however, it is necessary to study the characteristics of photosynthetic physiology of tobacco seedlings in WCST. Combined with the field and pot experiments, the study examined photosynthetic active radiation (PAR) level, plant height, leaf length, leaf width and chlorophyll content, and the leaf photosynthesis and maximal photochemical efficiency (Fv/Fm) of photosynthetic system II (PSII) were analyzed in WCST, compared with CT. The results showed that PAR levels in WCST were decreased (i.e, such that PAR levels were 72.60% and 52.85% at 4 cm and 8 cm in WCST respectively, compared with the CT). Plant height, leaf length and leaf width of tobacco seedlings were improved, but the leaf chlorophyll contents were reduced in WCST. In WCST, the maximum net photosynthetic rates (Pmax) and the light saturation points (LSP) were decreased and the light compensation points (LCP) and dark respiration rates (Rd) were reduced by 20.43% and 17.78% respectively. The apparent quantum yield (AQY) was improved by 4.44%, compared to CT. PSII maximal photochemical efficiency (Fv/Fm) of tobacco seedlings was reduced when transplanted in WCST or CT, but the Fv/Fm of transplanted seedlings was significantly (P < 0.05) higher by 5% to 9% in WCST than in CT. The growth of tobacco seedlings transplanted by WCST was accelerated in WCST. The self-adaptation and the enhanced light use efficiency in a weak light environment may provide a physiological basis to promote tobacco growth.