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Canopy photosynthesis of CO 2 ‐enriched lettuce ( Lactuca sativa L.). Response to short‐term changes in CO 2 , temperature and oxides of nitrogen
Author(s) -
CAPORN S. J. M.,
HAND D. W.,
MANSFIELD T. A.,
WELLBURN A. R.
Publication year - 1994
Publication title -
new phytologist
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.742
H-Index - 244
eISSN - 1469-8137
pISSN - 0028-646X
DOI - 10.1111/j.1469-8137.1994.tb07528.x
Subject(s) - lactuca , photosynthesis , compensation point , respiration , canopy , chemistry , horticulture , nitrogen , botany , analytical chemistry (journal) , biology , environmental chemistry , transpiration , organic chemistry
SUMMARY The canopy net photosynthesis (P n ) of lettuce ( Lactuca sativa L. ev.‘Ambassador’) was analyzed under controlled conditions simulating the winter glasshouse atmosphere. Prior to measurements the plants were grown in CO 2 ‐enriched air of 1000 μmol mol −1 , at a photosynthetic photon flux density (PPFD) of 280 μmol m 2 s −1 (400–700 nm) and a day/night air temperature of 16/13 °C. Short‐term changes in CO 2 concentration significantly changed the initial gradient of the photosynthetic response to incident PPFD. Maximum photosynthetic efficiency of the crop increased from 0·041 mol CO 2 mol photons −1 (equivalent to 8·2 μg CO 2 J −1 and 9·4% on an energy basis) at 350 μmol mol −1 to 0·055 mol CO 2 photons −1 (10·9 μg CO 2 J −1 and 12·7% on an energy basis) at 1000 μmol mol −1 . Transfer from low to high CO 2 also lowered the light compensation point, but did not affect dark respiration. The large response of P n to transient changes in CO 2 indicated that the lettuce canopy did not acclimate to growth in 1000 μmol CO 2 mol −1 , in contrast with the effect of growth in high CO 2 on P n in single mature leaves reported earlier. A reduction in air temperature from 16 to 6 °C at a concentration of 1000 μmol CO 2 mol −1 halved the rate of dark respiration and reduced the light compensation point, but had no direct effect on the maximum efficiency with which the crop utilized light. Subsequently at low light (below 200 μmol m −1 s −1 ) P n was greater at 6 than 16 °C. Between a PPFD of 250 and 300 μmol m −2 s −1 canopy P n was similar at all temperatures. Addition of 2·0 μmol mol −1 nitric oxide to an atmosphere of 1000 μmol CO 2 mol −1 caused a rapid and reversible reduction of canopy P n , which was greater at the lowest temperatures. The average inhibition was 6·6 at 16 °C and 28·8% at 6 °C; this was not explained by differences in the rate of pollutant uptake, which was less in the cooler conditions. The results are discussed in relation to development of optimal growing conditions for production of glasshouse lettuce at low light and low temperature during winter in the UK.