Scientia Horticulturae: Gradually increasing light intensity during the growth period increases dry weight production compared to constant or gradually decreasing light intensity in lettuce

Gradually Increasing Light Intensity During The Growth Period Increases Dry Weight Production Compared To Constant Or Gradually Decreasing Light Intensity In Lettuce

Wenqing Jin, Yongran Ji, Dorthe H. Larsen, Yang Huang, Ep Heuvelink, Leo F.M. Marcelis

Abstract

The objective of this research was to investigate the effects of gradually increasing or decreasing photosynthetic photon flux density (PPFD) during cultivation compared to a constant PPFD on biomass production. Lettuce plants (Lactuca sativa L. ‘Expertise’) were grown in climate rooms in which every three days the PPFD was increased by 16 µmol m−2 s−1 (from 140 to 300 µmol m−2 s−1 from day 0 to 30), decreased (from 300 to 140 µmol m−2 s−1), or kept constant (221 µmol m−2 s−1), while the total light integral at the end of the cultivation period (30 d) was the same for all three treatments. Gradually increasing PPFD resulted in a 16 or 13% increase in total plant dry weight compared to treatments with decreasing or constant PPFD, respectively. This increase was explained by a higher light interception mainly because, in this treatment, most of the light was provided at the end of the cultivation period when the leaf area index was high. Consequently, the light use efficiency based on incident PPFD was highest when PPFD gradually increased, even though the light use efficiency based on intercepted PPFD was highest when PPFD gradually decreased during cultivation. Despite the higher shoot dry weight when PPFD gradually increased, shoot fresh weight was not significantly affected by the light treatments. This difference in response between fresh and dry weight resulted from a higher shoot dry matter content when PPFD gradually increased. Our results show that gradually increasing PPFD had a positive effect on dry weight accumulation and increased dry matter content, but did not affect the shelf life. So, although vertical farms enable growers to keep all conditions constant, some dynamic variation of conditions might be needed for optimizing the light use efficiency.

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Postharvest Biology and Technology: Far-red light during cultivation improves postharvest chilling tolerance in basil

Far-red light during cultivation improves postharvest chilling tolerance in basil

Dorthe H Larsen, Leo FM Marcelis, Diederick van Kempen, Wouter Kohlen, Celine CS Nicole, Ernst J Woltering

Abstract

Basil (Ocimum basilicum L.) is a temperature sensitive plant and suffers from chilling injury (CI), especially during the postharvest storage. We investigated the effect of additional far-red light (FR) during cultivation at two temperatures on postharvest chilling tolerance. Basil was cultivated under red-white Light Emitting Diodes (LED) at 25 °C. During the last 3 weeks before harvest, plants were maintained at a high temperature (25 ºC) or exposed to a low temperature (15 ºC). Furthermore, plants were exposed to additional FR (180 µmol m−2 s−1) for different durations (0, 1 or 3 weeks). After harvest, leaves were stored at 4 and 12 ºC in darkness. Overall visual quality and maximum quantum yield of PS II (Fv/Fm) as indicators of chilling injury were monitored every third day for 15 d. Abscisic acid (ABA) and jasmonic acid (JA), carbohydrates, and antioxidants were measured at harvest and after 9 d of storage at 4 °C. Additional FR improved the chilling tolerance at both cultivation temperatures. Cultivation temperature had no effect on postharvest chilling tolerance. Hormone levels in basil leaves at harvest were not affected by FR. This indicates that ABA and JA are not involved in development of FR-induced chilling tolerance in basil. FR had no effect on the levels of antioxidants at harvest whereas the levels of soluble sugars and starch increased under additional FR. The positive effect of adding FR during cultivation on chilling tolerance in basil may be due to the increase in soluble sugars and starch.

Nature Food: Current status and future challenges in implementing and upscaling vertical farming systems

Current status and future challenges in implementing and upscaling vertical farming systems

S. H. van Delden, M. SharathKumar, M. Butturini, L. J. A. Graamans, E. Heuvelink, M. Kacira, E. Kaiser, R. S. Klamer, L. Klerkx, G. Kootstra, A. Loeber, R. E. Schouten, C. Stanghellini, W. van Ieperen, J. C. Verdonk, S. Vialet-Chabrand, E. J. Woltering, R. van de Zedde, Y. Zhang & L. F. M. Marcelis

Abstract

Vertical farming can produce food in a climate-resilient manner, potentially emitting zero pesticides and fertilizers, and with lower land and water use than conventional agriculture. Vertical farming systems (VFS) can meet daily consumer demands for nutritious fresh products, forming a part of resilient food systems—particularly in and around densely populated areas. VFS currently produce a limited range of crops including fruits, vegetables and herbs, but successful implementation of vertical farming as part of mainstream agriculture will require improvements in profitability, energy efficiency, public policy and consumer acceptance. Here we discuss VFS as multi-layer indoor crop cultivation systems, exploring state-of-the-art vertical farming and future challenges in the fields of plant growth, product quality, automation, robotics, system control and environmental sustainability and how research and development, socio-economic and policy-related institutions must work together to ensure successful upscaling of VFS to future food systems.

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