Photosynthetic Efficiency and Anatomical Structure of Pepper Leaf (Capsicum annuum L.) Transplants Grown under High-Pressure Sodium (HPS) and Light-Emitting Diode (LED) Supplementary Lighting Systems.

Anna Sobczak,Katarzyna Kowalczyk,Waldemar Kowalczyk,Janina Gajc-Wolska,Wojciech Borucki,Hazem M Kalaji,Marzena Sujkowska-Rybkowska

doi:10.3390/plants10101975

Abstract

The aim of this study was to evaluate the effects of various supplemental greenhouse lighting systems, i.e., high-pressure sodium lamps and mixtures of red and blue light-emitting diodes, on the photochemical efficiency, anatomical leaf structure, and growth of the two pepper cultivars. The intensity levels of the photosynthetically active radiation were the same for both light treatments. In this study, the relative chlorophyll content was measured. Additionally, certain parameters of chlorophyll a fluorescence were measured under ambient light or after dark adaptation. The obtained results showed that the application of light-emitting diodes (LEDs) as supplemental lighting positively affected the anatomical leaf characteristics and plant growth. The leaves of both pepper cultivars were thicker and had larger palisade parenchyma cells under LED supplemental lighting compared to leaves grown under high-pressure sodium (HPS) lamps. Moreover, the mesophyll cells of seedlings grown under LEDs contained more chloroplasts than those growing under HPS lighting. The chlorophyll a fluorescence measurements of pepper seedlings grown under LEDs showed significant increases in photosynthetic apparatus performance index (PI) values compared to plants grown under HPS lamps; however, the values for this index were higher in cv. ‘Aifos’ as compared to cv. ‘Palermo’. We recommend that supplemental lighting systems are applied with caution, as their performance appears to depend not only on the light spectrum but also on the cultivar.

Highlights

Light is one of the essential factors in a plant’s growth, development, and yield [1,2,3]
Our study revealed that light-emitting diodes (LEDs) delivered a better blue-to-red (R/B) ratio than high-pressure sodium (HPS) lamps
This better supplemental lighting (LEDs) indirectly enhanced plant growth by increasing the height of the seedlings and the number of leaves; we found that this effect is cultivar-dependent

Summary

Introduction

Light is one of the essential factors in a plant’s growth, development, and yield [1,2,3]. Increasing attention is being focused on the promotion of efficient artificial light sources in lighted crops cultivated during periods when there is not enough natural light for proper plant growth and development This applies to crops grown during winter, as well as to seedling production for the earliest crop dates [8]. In moderate climate zones at northern latitudes, during autumn–winter and early spring there is a deficit of the natural light required for the optimal plant growth of most plants This is the time of year when seedlings of vegetables are usually prepared in greenhouses for the earliest cultivation dates [9]. They are usually grown under high-pressure sodium (HPS) lamps

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Conclusion