Schipper R, van der Meer M, de Visser P H B, Heuvelink E, Marcelis L F M
Horticulture and Product Physiology, Wageningen University, Wageningen, Netherlands.
Business Unit Greenhouse Horticulture, Wageningen Research, Wageningen, Netherlands.
Front Plant Sci. 2023 Jan 19;14:1012529. doi: 10.3389/fpls.2023.1012529. eCollection 2023.
In the past decade, the potential of positioning LED lamps in between the canopy (intra-canopy) to enhance crop growth and yield has been explored in greenhouse cultivation. Changes in spatial heterogeneity of light absorption that come with the introduction of intra-canopy lighting have not been thoroughly explored. We calibrated and validated an existing functional structural plant model (FSPM), which combines plant morphology with a ray tracing model to estimate light absorption at leaflet level. This FSPM was used to visualize the light environment in a tomato crop illuminated with intra-canopy lighting, top lighting or a combination of both. Model validation of light absorption of individual leaves showed a good fit (R = 0.93) between measured and modelled light absorption of the canopy. Canopy light distribution was then quantified and visualized in three voxel directions by means of average absorbed photosynthetic photon flux density (PPFD) and coefficient of variation (CV) within that voxel. Simulations showed that the variation coefficient within horizontal direction was higher for intra-canopy lighting than top lighting (CV=48% versus CV= 43%), while the combination of intra-canopy lighting and top lighting yielded the lowest CV (37%). Combined intra-canopy and top lighting (50/50%) had in all directions a more uniform light absorption than intra-canopy or top lighting alone. The variation was minimal when the ratio of PPFD from intra-canopy to top lighting was about 1, and increased when this ratio increased or decreased. Intra-canopy lighting resulted in 8% higher total light absorption than top lighting, while combining 50% intra-canopy lighting with 50% top lighting, increased light absorption by 4%. Variation in light distribution was further reduced when the intra-canopy LEDs were distributed over strings at four instead of two heights. When positioning LED lamps to illuminate a canopy both total light absorption and light distribution have to be considered.
在过去十年中，人们探索了在温室栽培中将LED灯置于冠层之间（冠层内）以提高作物生长和产量的潜力。冠层内照明引入后光吸收空间异质性的变化尚未得到充分研究。我们校准并验证了一个现有的功能结构植物模型（FSPM），该模型将植物形态与光线追踪模型相结合，以估计小叶水平的光吸收。这个FSPM被用来可视化番茄作物在冠层内照明、顶部照明或两者结合照明下的光环境。对单叶光吸收的模型验证表明，冠层实测光吸收与模型光吸收之间拟合良好（R = 0.93）。然后通过体素内的平均吸收光合光子通量密度（PPFD）和变异系数（CV）在三个体素方向上对冠层光分布进行量化和可视化。模拟表明，冠层内照明水平方向的变异系数高于顶部照明（CV = 48%对CV = 43%），而冠层内照明和顶部照明相结合产生的CV最低（37%）。冠层内照明和顶部照明相结合（50/50%）在所有方向上的光吸收都比单独的冠层内照明或顶部照明更均匀。当冠层内PPFD与顶部照明的比例约为1时，变异最小，当该比例增加或减少时，变异增加。冠层内照明导致的总光吸收比顶部照明高8%，而将50%的冠层内照明与50%的顶部照明相结合，光吸收增加了4%。当冠层内LED灯分布在四个而不是两个高度的绳子上时，光分布的变异进一步减小。在定位LED灯以照亮冠层时，必须同时考虑总光吸收和光分布。
