Adams, S. R. (Steven R.), Valdes, V. M. and Langton, F.A. (2008) Why does low intensity, long-day lighting promote growth in Petunia, Impatiens, and tomato? Journal of Horticultural Science and Biotechnology, Vol.83 (No.5). pp. 609-615. ISSN 1462-0316.

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Abstract

Numerous reports demonstrate that low intensity, long-day (LD) lighting treatments can promote growth. However,
there are conflicting suggestions as to the mechanisms involved. This study examines the responses of Petunia,
Impatiens, and tomato to LD lighting treatments and concludes that no single mechanism can explain the growth
promotion observed in each case. Petunia showed the most dramatic response to photoperiod; up to a doubling in dry
weight (DW) as a result of increasing daylength from 8 h d–1 to 16 h d–1.This could be explained by an increase in specific leaf area (SLA) comparable to that seen with shading. At low photosynthetic photon flux densities (PPFD), the increased leaf area more than compensated for any loss in photosynthetic capacity per unit leaf area. In Petunia, the response may, in part, have also been due to changes in growth habit. Impatiens and tomato showed less dramatic increases in DW as a result of LD lighting, but no consistent effects on SLA or growth habit were observed. In tomato, increased growth was accompanied by increased chlorophyll content, but this had no significant effect on
photosynthesis. In both species, increased growth may have been due to a direct effect of LD lighting on photosynthesis.
This is contrary to the generally held view that light of approx. 3 – 4 μmol m–2 s–1 is unlikely to have any significant impact on net photosynthesis. Nevertheless, we show that the relationship between PPFD and net photosynthesis is non-linear at low light levels, and therefore low intensity LD lighting can offset respiration very efficiently.
Furthermore, a small increase in photosynthesis will have a greater impact when ambient light levels are low.

Item Type:	Journal Article
Subjects:	S Agriculture > SB Plant culture
Divisions:	Faculty of Science, Engineering and Medicine > Science > Life Sciences (2010- ) > Warwick HRI (2004-2010)
Library of Congress Subject Headings (LCSH):	Plant photoperiodism, Plants -- Effect of light on, Photosynthesis
Journal or Publication Title:	Journal of Horticultural Science and Biotechnology
Publisher:	Headley Bros. Ltd.
ISSN:	1462-0316
Official Date:	September 2008
Dates:	Date Event September 2008 Published
Volume:	Vol.83
Number:	No.5
Page Range:	pp. 609-615
Status:	Peer Reviewed
Access rights to Published version:	Open Access (Creative Commons)
Funder:	Great Britain. Dept. for Environment, Food & Rural Affairs (DEFRA)
Grant number:	HH3603SPC

Data sourced from Thomson Reuters' Web of Knowledge

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