Light‐limited photosynthesis under energy‐saving film decreases eggplant yield

Sachin G Chavan,Michael E Loik,Charles R Warren,David T Tissue,Oula Ghannoum,Joao C Filipe,Chelsea Maier,Han Lin,Yagiz Alagoz,Christopher I Cazzonelli,Baohua Jia,Zhonghua H Chen

doi:10.1002/fes3.245

Abstract

AbstractGlasshouse films with adjustable light transmittance and energy‐efficient designs have the potential to reduce (up to 80%) the high energy cost for greenhouse horticulture operations. Whether these films compromise the quantity and quality of light transmission for photosynthesis and crop yield remains unclear. A “Smart Glass” film ULR‐80 (SG) was applied to a high‐tech greenhouse horticulture facility, and two experimental trials were conducted by growing eggplant (Solanum melongena) using commercial vertical cultivation and management practices. SG blocked 85% of ultraviolet (UV), 58% of far‐red, and 26% of red light, leading to an overall reduction of 19% in photosynthetically active radiation (PAR, 380–699 nm) and a 25% reduction in total season fruit yield. There was a 53% (season mean) reduction in net short‐wave radiation (radiometer range, 385–2,105 nm upward; 295–2,685 nm downward) that generated a net reduction of 8% in heat load and reduced water and nutrient consumption by 18%, leading to improved energy and resource use efficiency. Eggplant adjusted to the altered SG light environment via decreased maximum light‐saturated photosynthetic rates (Amax) and lower xanthophyll de‐epoxidation state. The shift in light characteristics under SG led to reduced photosynthesis, which may have reduced source (leaf) to sink (fruit) carbon distribution, increased fruit abortion and decreased fruit yield, but did not affect nutritional quality. We conclude that SG increases energy and resource use efficiency, without affecting fruit quality, but the reduction in photosynthesis and eggplant yield is high. The solution is to re‐engineer the SG to increase penetration of UV and PAR, while maintaining blockage of glasshouse heat gain.

Highlights

With declining cultivable agricultural land (Roser & Ritchie, 2019) and growing food demand, crop production depends on higher yield through technological advancements and crop improvement
Reductions in PAR reduced photosynthesis in leaves from SG grown plants, which was associated with a decrease in yield due mainly to higher fruit abortion rates, without affecting fruit quality
It should be noted that SG is likely to have different effects in a crop-specific manner and during periods of primarily low light, including winter growing periods

Summary

Introduction

With declining cultivable agricultural land (Roser & Ritchie, 2019) and growing food demand, crop production depends on higher yield through technological advancements and crop improvement. The study by Loik et al, (2017) investigated the use of wavelength-selective photovoltaic systems (WSPVs), which absorbed some of the blue and green wavelengths of the solar spectrum for electricity generation but transmitted remaining wavelengths including most of the red light, on tomato production. They measured the effect of altered light on photosynthesis and yield and suggested further studies on assessing photosynthesis in different crops and climates, in response to altered light environments (Loik et al, 2017)

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