Effects of different nitrogen forms on photosynthetic rate and the chlorophyll fluorescence induction kinetics of flue-cured tobacco

Abstract

Net photosynthetic rate (P N ) of tobacco plants grown with NH 4 -N as the only N source was the lowest all the times, while P N grown only with NO 3 -N was the greatest until 22 nd day, and P N grown with both NO 3 -N and NH 4 -N (1 : 1) was the greatest. Maximal photochemical efficiency of photosystem 2 (PS2), F v /F m , and actual quantum yield of PS2 under actinic irradiation ( PS2 ) in plants grown with only NH 4 -N were greatest at early stage and then decreased and were smaller than those of other treatments. Photochemical quenching coefficient (q P ) and non-photochemical quenching coefficient (q NP ) in the NH 4 -N plants were the greatest at all times. Hence excessive NH 4 -N can decrease not only photochemical efficiency but also the efficiency of utilization of photon energy absorbed by pigments for photosynthesis. Therefore, excessive NH 4 -N is a hindrance to photosynthesis of flue-cured tobacco. On the other hand, tobacco cultured with an appropriate mixture of NO 3 -N with NH 4 -N can sufficiently utilize photon energy and increase the efficiency of energy transformation.Additional key words: actual quantum yield of PS2; Nicotiana; photochemical and non-photochemical quenching; photosystem 2. --Photosynthesis is a basic physiological process in crop production. In order to increase output, diversified cultivation measures are adopted to improve photosynthetic capability of crops (Dong et al. 1991). Nitrogen is the main constituent of proteins, chlorophyll (Chl), and enzymes involved in photosynthesis. Therefore, nitrogen affects photosynthesis of crops. The nitrogen absorbed by plants mostly includes NO 3 -N and NH 4 + -N, and their uptake, deposition, and assimilation in crops are different. There have been many studies on the effects of N forms on photosynthesis, growth, yield, and quality of tobacco, but the relationship of nitrogen forms to energy conversion and distribution in photosynthesis has rarely been researched (Han 1996, Feng and Peng 1998, Yang et al. 1999. In order to provide a theoretical basis for the cultivation techniques of good quality and high yield tobacco, we studied the effects of N forms on Chl fluorescence and photosynthesis.Tobacco seedlings (cv. K326) having 8 leaves were cultured in the nutrient solution [g m -3 ] N 40,

Comparative photosynthesis characteristics of Calycanthus chinensis and Chimonanthus praecox

“…High q P is advantageous for the separation of electric charge in the RC, and the ability to transport electrons and the quantum yield of PS2 are enhanced (Guo et al 2006). According to our results, the values of q P of the two species were both about 1.0.…”

“…The higher q NP in C. praecox showed that the energy absorbed in the physiological range of irradiances might be much higher than photochemical utilization. The lower q NP in C. chinensis indicated that this species can effectively reduce the thermal dissipation and utilize energy absorbed by antenna pigments in PS2 for photosynthesis (Guo et al 2006). Thus, compared with C. praecox, C. chinensis was more appropriate to the thermal dissipation and had more advantages under the same irradiance.…”

Shading tolerance in rice is related to better light harvesting and use efficiency and grain filling rate during grain filling period

“…This might be due to the reduction in efficiency of excitation capture (Dai et al, 2009), as exemplified by the sharp decreased in J max under the shading conditions. Dai et al (2009) and Mao et al (2007) suggested that it was beneficial for electric charge separation in the reaction center to have a higher qP, and that a more efficient use of the absorbed energy in PSII was indicated by a lower NPQ (Guo et al, 2006). In this study, the chlorophyll fluorescence characteristics were closely related to rice variety.…”

Effects of nitrogen addition on growth and photosynthetic characteristics of Acer truncatum seedlings

“…However, our study did not support this expectation, as Yield was comparatively stable under moderate and high nitrogen conditions when qN increased. This may be due to the increase of qP, since high qP is advantageous for the separation of the electric charge in the reaction center, and is beneficial to electron transport and PSII yield (Dai et al 2009;Guo et al 2006). This observation was confirmed by the relatively high Etr of high and moderate nitrogen addition seedlings.…”