Elsevier Science Publishers B.V., Amsterdam - - Printed in The Netherlands
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I n f l u e n c e of L i g h t on the G r o w t h of Y o u n g Tomato, Cucumber and S w e e t P e p p e r P l a n t s in t h e Greenhouse: Effects on R e l a t i v e G r o w t h Rate, Net A s s i m i l a t i o n Rate and L e a f Area Ratio
G.T. BRUGGINK and E. HEUVELINK
Department of Horticulture, Agricultural University, P.O. Box 30, 6700 AA Wageningen (The Netherlands)
Publication No. 526 (Accepted for publication 22 October 1986 )
ASR C BT A T
Bruggink, G.T. and Heuvelink, E., 1987. Influence of light on the growth of young tomato, cucumber and sweet pepper plants in the greenhouse: effects on relative growth rate, net assimilation rate and leaf area ratio. Scientia Hortic., 31: 161-174. Tomato, cucumber and sweet pepper were sown in a greenhouse at regular intervals throughout the year. A relationship between the relative growth rate (RGR) of these young plants and the mean daily light integral ( PAR incoming per unit ground area) could be calculated for each species. A growth analysis was made over 4 dry-weight intervals between 20 and 2460 rag. RGR for cucumber and tomato were about the same; RGR for sweet pepper was about 25% lower. RGR can be regarded as the product of net assimilation rate (NAR) and leaf area ratio (LAR). NAR appeared to be almost the same for all three species in our experiment. At low light intensities, the NAR of tomato plants reacted the most strongly to changes in light intensity (highest light-use efficiency). The lower relative growth rate for sweet pepper was due to its lower LAR value, caused by the fact that it has thicker leaves than cucumber and tomato. NAR was at its maximum level when the mean daily light integral was approximately 400 J cm-2 day-~ or more (light saturation). RGR reached a maximum level at a mean daily light integral of about 300 J cm- 2 day- i. This difference was caused by
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