Photosynthetica

, Volume 49, Issue 4, pp 507–514

Differential responses of leaf water-use efficiency and photosynthetic nitrogen-use efficiency to fertilization in Bt-introduced and conventional rice lines

Original Papers

DOI: 10.1007/s11099-011-0060-9

Cite this article as:
Guo, R.Q., Ruan, H., Yang, W.J. et al. Photosynthetica (2011) 49: 507. doi:10.1007/s11099-011-0060-9

Abstract

Leaf stomatal conductance (gs), transpiration rate (E), and light-saturated net photosynthetic rate (PNmax) at three developmental stages (tillering stage, jointing-booting stage, and milking stage) and leaf total nitrogen concentration (LTNC) and δ13C value at milking stage were measured for a conventional rice line (Minghui 63) and its corresponding Bacillus thuringiensis (Bt)-gene [cry1A (b and c)] introduced line (Bt line) under three fertilizer levels. Compared to conventional line, Bt line showed lower gs, which was associated with lower PNmax and E, but instantaneous water-use efficiency (WUE), measured as the ratio of PNmax to E, was higher in the Bt line than in the conventional line, particularly in the jointing-booting stage. However, δ13C values were not significantly different across treatments, suggesting that intrinsic water-use efficiency (WUEin) might be indistinguishable between Bt and conventional lines. LTNC was higher but PNmax was lower in Bt line compared to conventional line, resulting in significantly lower photosynthetic nitrogen-use efficiency (PNUE). This might result from the additional cost of producing Bt protein in the Bt line due to the effect of competing nitrogen with photosynthetic machinery. Bt-gene introduction and expression does not significantly change WUEin but may significantly decrease leaf PNUE. Thus we suggest that Bt rice should be carefully examined in relation to environmental risks (e.g. water-body pollution) before planting commercially.

Additional key words

Bacillus thuringiensis rice δ13instantaneous water-use efficiency intrinsic water-use efficiency photosynthetic nitrogen-use efficiency stomatal conductance 

Abbreviations

Bt

Bacillus thuringiensis

E

transpiration rate

gs

stomatal conductance

LTNC

leaf total nitrogen concentration

PNmax

light-saturated net photosynthetic rate

PAR

photosynthetic active radiation

PNUE

photosynthetic nitrogen-use efficiency

RH

air relative humidity

WUE

instantaneous water-use efficiency

WUEin

intrinsic water-use efficiency

δ13C

the difference in 13C/12C ratio between sample material and standard material

Copyright information

© Springer Science+Business Media B.V. 2011

Authors and Affiliations

  1. 1.Department of BiologyNanjing UniversityNanjingChina
  2. 2.Nanjing Institute of Environmental SciencesMinistry of Environmental Protection of ChinaNanjingChina

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