Department of Plant Sciences, Horticultural Supply Chains Group, Wageningen University, Wageningen, the Netherlands.
Physiol Plant. 2010 Mar;138(3):289-300. doi: 10.1111/j.1399-3054.2009.01333.x. Epub 2009 Nov 19.
Mathematical models of light attenuation and canopy photosynthesis suggest that crop photosynthesis increases by more uniform vertical irradiance within crops. This would result when a larger proportion of total irradiance is applied within canopies (interlighting) instead of from above (top lighting). These irradiance profiles can be generated by Light Emitting Diodes (LEDs). We investigated the effects of interlighting with LEDs on light interception, on vertical gradients of leaf photosynthetic characteristics and on crop production and development of a greenhouse-grown Cucumis sativus'Samona' crop and analysed the interaction between them. Plants were grown in a greenhouse under low natural irradiance (winter) with supplemental irradiance of 221 micromol photosynthetic photon flux m(-2) s(-1) (20 h per day). In the interlighting treatment, LEDs (80% Red, 20% Blue) supplied 38% of the supplemental irradiance within the canopy with 62% as top lighting by High-Pressure Sodium (HPS)-lamps. The control was 100% top lighting (HPS lamps). We measured horizontal and vertical light extinction as well as leaf photosynthetic characteristics at different leaf layers, and determined total plant production. Leaf mass per area and dry mass allocation to leaves were significantly greater but leaf appearance rate and plant length were smaller in the interlighting treatment. Although leaf photosynthetic characteristics were significantly increased in the lower leaf layers, interlighting did not increase total biomass or fruit production, partly because of a significantly reduced vertical and horizontal light interception caused by extreme leaf curling, likely because of the LED-light spectrum used, and partly because of the relatively low irradiances from above.
光衰减和冠层光合作用的数学模型表明，作物光合作用会随着冠层内更均匀的垂直辐照度而增加。当更多的总辐照度应用于冠层内（内透光）而不是来自上方（顶光）时，就会产生这种辐照度分布。这些辐照度分布可以通过发光二极管（LED）产生。我们研究了 LED 内透光对光截获、叶片光合作用特性垂直梯度以及温室种植的黄瓜（Cucumis sativus 'Samona'）作物的生长发育的影响，并分析了它们之间的相互作用。在冬季低自然光照条件下，在温室中种植植物，用 221 微摩尔光合光子通量 m(-2) s(-1)（每天 20 小时）补充光照。在内透光处理中，LED（80%红，20%蓝）提供了冠层内 38%的补充光照，62%的光照由高压钠（HPS）灯提供顶光。对照处理是 100%顶光（HPS 灯）。我们测量了不同叶片层的水平和垂直光衰减以及叶片光合作用特性，并确定了总植物产量。内透光处理的叶面积质量和干物质分配到叶片的比例显著增加，但叶出现率和植株长度较小。尽管下部叶片的光合作用特性显著提高，但内透光并没有增加总生物量或果实产量，部分原因是由于叶片极度卷曲导致垂直和水平光截获显著减少，这可能是由于使用的 LED 光光谱，部分原因是来自上方的相对低辐照度。
