A Chlorophyll Fluorescence-based Biofeedback System to Control Photosynthetic Lighting in Controlled Environment Agriculture

Photosynthetic lighting is one of the main costs of running controlled environment agriculture facilities. To optimize photosynthetic lighting, it is important to understand how plants use the provided light. When photosynthetic pigments absorb photons, the energy from those photons is used to drive the light reactions of photosynthesis, thermally dissipated, or re-emitted by chlorophyll as fluorescence. Chlorophyll fluorescence measurements can be used to determine the quantum yield of photosystem II (ΦPSII) and nonphotochemical quenching (NPQ), which is indicative of the amount of absorbed light energy that is dissipated as heat. Our objective was to develop and test a biofeedback system that allows for the control of photosynthetic photon flux density (PPFD) based on the physiological performance of the plants. To do so, we used a chlorophyll fluorometer to measure ΦPSII, and used these data and PPFD to calculate the electron transport rate (ETR) through PSII. A datalogger then adjusted the duty cycle of the light-emitting diodes (LEDs) based on the ratio of the measured ETR to a predefined target ETR (ETRT). The biofeedback system was able to maintain ETRs of 70 or 100 µmol·m−2·s−1 over 16-hour periods in experiments conducted with lettuce (Lactuca sativa). With an ETRT of 70 µmol·m−2·s−1, ΦPSII was stable throughout the 16 hour and no appreciable changes in PPFD were needed. At an ETRT of 100 µmol·m−2·s−1, ΦPSII gradually decreased from 0.612 to 0.582. To maintain ETR at 100 µmol·m−2·s−1, PPFD had to be increased from 389 to 409 µmol·m−2·s−1, resulting in a gradual decrease of ΦPSII and an increase in NPQ. The ability of the biofeedback system to achieve a range of different ETRs within a single day was tested using lettuce, sweetpotato (Ipomoea batatas), and pothos (Epipremnum aureum). As the ETRT was gradually increased, the PPFD required to achieve that ETR also increased, whereas ΦPSII decreased. Surprisingly, a subsequent decrease in ETRT, and in the PPFD required to achieve that ETR, resulted in only a small increase in ΦPSII. This indicates that ΦPSII was reduced because of photoinhibition. Our results show that the biofeedback system is able to maintain a wide range of ETRs, while it also is capable of distinguishing between NPQ and photoinhibition as causes for decreases in ΦPSII.

Download Full-text

Morphological and Physiological Screening to Predict Lettuce Biomass Production in Controlled Environment Agriculture

Remote Sensing ◽

10.3390/rs14020316 ◽

2022 ◽

Vol 14 (2) ◽

pp. 316

Author(s):

Changhyeon Kim ◽

Marc W. van Iersel

Keyword(s):

Incident Light ◽

Dry Weight ◽

Photosynthetic Photon Flux Density ◽

Rapid Screening ◽

Photon Flux ◽

Photon Flux Density ◽

Controlled Environment ◽

Anthocyanin Content ◽

Fast Growing ◽

Controlled Environment Agriculture

Fast growth and rapid turnover is an important crop trait in controlled environment agriculture (CEA) due to its high cost. An ideal screening approach for fast-growing cultivars should detect desirable phenotypes non-invasively at an early growth stage, based on morphological and/or physiological traits. Hence, we established a rapid screening protocol based on a simple chlorophyll fluorescence imaging (CFI) technique to quantify the projected canopy size (PCS) of plants, combined with electron transport rate (ETR) measurements using a chlorophyll fluorometer. Eleven lettuce cultivars (Lactuca sativa), selected based on morphological differences, were grown in a greenhouse and imaged twice a week. Shoot dry weight (DW) of green cultivars at harvest 51 days after germination (DAG) was correlated with PCS at 13 DAG (R2 = 0.74), when the first true leaves had just appeared and the PCS was <8.5 cm2. However, early PCS of high anthocyanin (red) cultivars was not predictive of DW. Because light absorption by anthocyanins reduces the amount of photons available for photosynthesis, anthocyanins lower light use efficiency (LUE; DW/total incident light on canopy over the cropping cycle) and reduce growth. Additionally, the total incident light on the canopy throughout the cropping cycle explained 90% and 55% of variability in DW within green and red cultivars, respectively. Estimated leaf level ETR at a photosynthetic photon flux density (PPFD) of 200 or 1000 µmol m−2 s−1 were not correlated with DW in either green or red cultivars. In conclusion, early PCS quantification is a useful tool for the selection of fast-growing green lettuce phenotypes. However, this approach may not work in cultivars with high anthocyanin content because anthocyanins direct excitation energy away from photosynthesis and growth, weakening the correlation between incident light and growth.

Download Full-text

Response of Sonia roses to continuous daytime CO2 supplementation under controlled environment conditions

Australian Journal of Agricultural Research ◽

10.1071/ar9880863 ◽

1988 ◽

Vol 39 (5) ◽

pp. 863 ◽

Cited By ~ 3

Author(s):

M Zeroni ◽

J Gale

Keyword(s):

Leaf Area ◽

Photosynthetic Photon Flux Density ◽

Photon Flux ◽

Photon Flux Density ◽

Controlled Environment ◽

Flower Bud ◽

Flower Yield ◽

Co2 Concentrations ◽

Water Vapour Diffusion ◽

Flower Quality

Rose plants (Rosa hybrida cv. Sonia, Syn. Sweet Promise) were placed in growth chambers under conditions resembling winter in a controlled environment greenhouse in the desert: mild temperatures, high incident photosynthetic photon flux density (PPFD), high air humidity and 10.5 h daylenght. Concentrations of CO2 in the air were maintained throughout the day at 320, 600 or 1200 8l l-1 with approximately 350 8l l-1 at night. Plant growth (length, fresh and gry weight), development (breaks, blindness), flower yield and flower quality (flower bud diameter, fresh weight and cane length) indices were monitored throughout three consecutive flowering cycles. CO2 supplementation caused an increase in leaf resistance to water vapour diffusion, accompanied by a reduction in the rate of transpiration per unit leaf area, Total leaf area increased at higher CO2 concentrations. Water use per plant did not change. Plant water potentials increased with rising CO2 concentrations. Growth, development, flower yield and flower quality were greatly enahnced in the CO2-enriched atmosphere. The response of growth and development to CO2 supplementation tended to decrease slightly with time when calculated per branch, but increased when calculated per plant. Flower yield and qualtiy did not change with time. The highest CO2 treatment resulted in a sustained, approximately 50% increase in yield, and doubling of the above quality indices throughout the three growth cycles.

Download Full-text

What Limits the Efficiency of Photosynthesis, and Can There Be Beneficial Improvements?

Feeding a World Population of More Than Eight Billion People ◽

10.1093/oso/9780195113129.003.0015 ◽

1998 ◽

Author(s):

J. Barber

Keyword(s):

Carbon Dioxide ◽

Molecular Mechanisms ◽

Photon Flux ◽

Photon Flux Density ◽

Sufficient Information ◽

A Value ◽

Wide Range ◽

Rate Of Photosynthesis ◽

Main Factors

Over the past 35 years a great deal has been learned about the mechanisms of photosynthesis, ranging from the ultrafast reactions involved in the initial capture of photons to the slower processes of carbon metabolism. Today our knowledge of photosynthesis and its molecular mechanisms is enormous, so much so that it is difficult for one person to absorb all the information. This is not necessarily a bad thing, since what we have achieved is sufficient information to appreciate the complexity of the “photosynthetic engine” and to identify the main factors that ultimately regulate its efficiency. In this chapter I summarize those areas of photosynthesis research with which I am reasonably familiar and, in so doing, address the question posed by the chapter title. As Blackman (1895a,b) pointed out, the rate of photosynthesis initially rises as the light intensity is increased and then levels off to a plateau. This plot is often referred to as the rate v PFD curve, where PFD stands for Photon Flux Density. Over the years rigorous analyses of the slopes of the rate v PFD curve have been made to obtain a value of the quantum yield (usually expressed as the number of quanta or photons required to produce one molecule of oxygen or to fix one molecule of carbon dioxide). With a few exceptions, the value obtained for a wide range of “non stressed” organisms and plants supplied with excess CO2 is about 9 or a little more (Björkman and Demmig, 1987; Walker, 1992). Bearing in mind that one molecule of oxygen evolved or carbon dioxide fixed is a 4e/4H+ process, then a value of 8 would he consistent with the “Z-scheme” model proposed by Hill and Bendall (1960). In this scheme, each electron is excited twice, first by photosystem two (PSII) and then by photosystem one (PSI). In this way, 8 photons are used to drive 4e/4H+ from water, through PSII and PSI to NADP.

Download Full-text

Quantitative Mapping of Leaf Photosynthesis Using Chlorophyll Fluorescence Imaging

Functional Plant Biology ◽

10.1071/pp9950277 ◽

1995 ◽

Vol 22 (2) ◽

pp. 277 ◽

Cited By ~ 76

Author(s):

B Genty ◽

S Meyer

Keyword(s):

Chlorophyll Fluorescence ◽

Electron Transport ◽

Quantum Yield ◽

Co2 Assimilation ◽

Linear Electron ◽

Leaf Photosynthesis ◽

Heterogeneous Distribution ◽

Fluorescence Measurements ◽

Wide Range ◽

Photochemical Yield

A method has been developed for routine, non-invasive monitoring of the topography of leaf photochemistry. The method uses video images of leaf chlorophyll fluorescence, taken during steady-state photosynthesis and during a transitory saturation of photochemistry, to construct, pixel by pixel, an image of the photochemical yield of photosystem II (PSII). The photochemical yield of PSII was estimated according to Genty et al. (1989) (Biochimica et Biophysica Acta 990, 87-92). The effectiveness of the method was shown by mapping the heterogeneous distribution of photosynthetic activity after treatment with either a herbicide (DCMU), abscisic acid, or during the course of the induction of photosynthesis. Leaf CO2 assimilation was simultaneously monitored under non- photorespiratory conditions to estimate the average quantum yield of linear electron transport. A unique proportional relationship was found between the mean photochemical yield of PSII calculated from images of the photochemical yield of PSII, and the average quantum yield of linear electron transport in three plant species exposed to a wide range of treatments or conditions. This new ability to quantitatively visualise leaf photochemistry provides a powerful tool to probe the spatial distribution of leaf photosynthesis. Possible errors in estimating the photochemical yield of PSII from mean fluorescence measurements are discussed.

Download Full-text

Effect of Different Ratios of Blue and Red LED Light on Brassicaceae Microgreens under a Controlled Environment

Plants ◽

10.3390/plants10040801 ◽

2021 ◽

Vol 10 (4) ◽

pp. 801

Author(s):

Aušra Brazaitytė ◽

Jurga Miliauskienė ◽

Viktorija Vaštakaitė-Kairienė ◽

Rūta Sutulienė ◽

Kristina Laužikė ◽

...

Keyword(s):

Nutritional Value ◽

Growth Parameters ◽

Light Emitting Diode ◽

Dry Mass ◽

Mineral Nutrients ◽

Photon Flux ◽

Photon Flux Density ◽

Controlled Environment ◽

Red Led ◽

Positive Effect

The consumption of microgreens has increased due to their having higher levels of bioactive compounds and mineral nutrients than mature plants. The lighting conditions during the cultivation of microgreens, if optimally selected, can have a positive effect by further increasing their nutritional value. Thus, our study aimed to determine the changes in mineral nutrients contents of Brassicaceae microgreens depending on different blue–red (B:R) light ratios in light-emitting diode (LED) lighting and to evaluate their growth and nutritional value according to different indexes. Experiments were performed in controlled environment growth chambers at IH LRCAF, 2020. Microgreens of mustard (Brassica juncea ‘Red Lace’) and kale (Brassica napus ‘Red Russian’) were grown hydroponically under different B:R light ratios: 0%B:100%R, 10%B:90%R, 25%B:75%R, 50%B:50%R, 75%B:25%R, and 100%B:0%R. A 220 μmol m−2 s−1 total photon flux density (TPFD), 18 h photoperiod, 21/17 ± 2 °C temperature and 60% ± 5% relative humidity in the growth chamber were maintained during cultivation. We observed that an increasing percentage of blue light in the LED illumination spectrum during growth was associated with reduced elongation in the microgreens of both species and had a positive effect on the accumulation of mostly macro- and micronutrients. However, different B:R light ratios indicate a species-dependent response to changes in growth parameters such as leaf area, fresh and dry mass, and optical leaf indexes such as for chlorophyll, flavonol, anthocyanin, and carotenoid reflectance.

Download Full-text

Pre-Harvest UV-B Radiation and Photosynthetic Photon Flux Density Interactively Affect Plant Photosynthesis, Growth, and Secondary Metabolites Accumulation in Basil (Ocimum Basilicum) Plants

Agronomy ◽

10.3390/agronomy9080434 ◽

2019 ◽

Vol 9 (8) ◽

pp. 434 ◽

Cited By ~ 7

Author(s):

Haijie Dou ◽

Genhua Niu ◽

Mengmeng Gu

Keyword(s):

Phenolic Compounds ◽

Flux Density ◽

Photosynthetic Photon Flux Density ◽

Ocimum Basilicum ◽

Photon Flux ◽

Photon Flux Density ◽

Yield Reduction ◽

Controlled Environment ◽

Photosynthetic Photon Flux ◽

Plant Yield

Phenolic compounds in basil (Ocimum basilicum) plants grown under a controlled environment are reduced due to the absence of ultraviolet (UV) radiation and low photosynthetic photon flux density (PPFD). To characterize the optimal UV-B radiation dose and PPFD for enhancing the synthesis of phenolic compounds in basil plants without yield reduction, green and purple basil plants grown at two PPFDs, 160 and 224 μmol·m−2·s−1, were treated with five UV-B radiation doses including control, 1 h·d−1 for 2 days, 2 h·d−1 for 2 days, 1 h·d−1 for 5 days, and 2 h·d−1 for 5 days. Supplemental UV-B radiation suppressed plant growth and resulted in reduced plant yield, while high PPFD increased plant yield. Shoot fresh weight in green and purple basil plants was 12%–51% and 6%–44% lower, respectively, after UV-B treatments compared to control. Concentrations of anthocyanin, phenolics, and flavonoids in green basil leaves increased under all UV-B treatments by 9%–18%, 28%–126%, and 80%–169%, respectively, and the increase was greater under low PPFD compared to high PPFD. In purple basil plants, concentrations of phenolics and flavonoids increased after 2 h·d−1 UV-B treatments. Among all treatments, 1 h·d−1 for 2 days UV-B radiation under PPFD of 224 μmol·m−2·s−1 was the optimal condition for green basil production under a controlled environment.

Download Full-text

Effects of artificial light sources on growth and phytochemicals content in green oak lettuce

Horticultura Brasileira ◽

10.1590/s0102-053620200213 ◽

2020 ◽

Vol 38 (2) ◽

pp. 204-210

Author(s):

Nursalmeeyah Etae ◽

Yarodah Wamae ◽

Weeraya Khummueng ◽

Tanyarath Utaipan ◽

Eaknarin Ruangrak

Keyword(s):

Energy Saving ◽

Flux Density ◽

Dry Mass ◽

Photon Flux ◽

Photon Flux Density ◽

Controlled Environment ◽

Artificial Light ◽

Light Sources ◽

Vegetable Production ◽

Artificial Lighting

ABSTRACT The artificial light source is one of the most important factors in a controlled environment for vegetable production. It could provide new opportunities to improve growth and increase phytochemicals content in vegetables. Therefore, this study focused on the effects of artificial light sources on growth and phytochemicals in green oak lettuce (Lactuca sativa). The plants were grown under growth chamber with three artificial light sources, namely bar-LED (the 1:1:1 ratio of blue 460 nm : red 630 nm : red 660 nm), bulb-LED (the 2:1:1 ratio of blue 460 nm : red 630 nm : red 660 nm), and fluorescent lamp (FL) (the wavelength range 380-700 nm) for 4 weeks. The quality of bar-LED light was better than either bulb-LED or FL, when assessed by the parameters of photosynthetically active radiation (PAR), photosynthetic photon flux density (PPFD, 400-700 nm), PPFD-B (blue, 400-500 nm), PPFD-R (red, 600-700 nm), the yield photon flux density (YPFD), and the color of red. However, shoot and root (fresh and dry mass), leaf area, leaf number, and shoot/root ratio did not significantly differ between plants grown under bar-LED and bulb-LED, but they were significantly higher than plants grown under FL. Bulb-LED and bar-LED induced larger dry mass of the plants than FL. The dry mass per mole of artificial lighting was highest in plants grown under bar-LED. On the other hand, the fresh mass per mole of artificial lighting was highest in plants grown under bulb-LED. As regards power consumption, bar-LED provided the lowest consumption with 44.4% energy saving over the FL. Total phenolic content, 2,2’-azino-bis (3-ethylbenzthiazoline-6-sulphonic acid) (ABTS) and 2,2-diphenylpicrylhydrazyl (DPPH) activities were highest in plants grown under bar-LED. FL lighting gave the least contents of chlorophyll a and chlorophyll a + b. However, chlorophyll b and carotenoid contents did not significantly differ among the treatments. Thus, the results suggested that bar-LED has the potential to improve energy saving, and both growth and phytochemicals content of green oak lettuce grown in a controlled environment of vegetable production.

Download Full-text

Hydraulic architecture of seedlings and adults of Rhizophora mangle L. in fringe and scrub mangrove

Botanical Sciences ◽

10.17129/botsci.2906 ◽

2021 ◽

Vol 1 (1) ◽

Author(s):

Diana J. Cisneros-de la Cruz ◽

Laura Yáñez-Espinosa ◽

Casandra Reyes-García ◽

Roberth Us-Santamaría ◽

José Luis Andrade

Keyword(s):

Water Potential ◽

Soil Water Potential ◽

Biosphere Reserve ◽

Rhizophora Mangle ◽

Conduction System ◽

Photon Flux ◽

Photon Flux Density ◽

Hydraulic Architecture ◽

Mangrove Plant ◽

Wide Range

Background: Mangrove plant species have distinctive anatomical and physiological responses to cope with a wide range of salinities and inundations. These strategies pertain a safe and efficient water use and transport, essential for survival. Questions: How are the anatomical and physiological attributes of the hydraulic architecture of seedlings and adults of Rhizophora mangle? what are the changes in hydraulic architecture of seedlings and adults of R. mangle in contrasting microenvironments? Studied species: Rhizophora mangle L. (Rhizophoraceae). Study site and dates: Scrub and fringe mangroves in Ria Celestún Biosphere Reserve, during the rainy season of 2013 (July to October). Methods: Hydraulic conductivity and leaf water potential, as well as xylem vessel density, length, transversal and radial diameter, and area were measured for seedlings and adults from both sites. The prevailing environmental conditions (soil water potential, salinity, photon flux density, air temperature and relative humidity) were also characterized. Results: A safer hydraulic conduction system, with narrow and more grouped vessels, was observed in seedlings than in adults of R. mangle in both sites. Adult individuals from the scrub mangrove, in the hyper saline microenvironment, had a safer hydraulic conduction system than adults in the fringe mangrove. Conclusions: The seedling stage of R. mangle showed a safer hydraulic system than adults in both types of mangroves. However, over time this hydraulic conduction system could become more efficient or remain safe depending on the microenvironment in which individuals are growing.

Download Full-text

Micropropagated dwarf off-type Cavendish bananas (Musa spp., AAA) show improved tolerance to suboptimal temperatures

Australian Journal of Agricultural Research ◽

10.1071/a96168 ◽

1997 ◽

Vol 48 (3) ◽

pp. 377 ◽

Cited By ~ 11

Author(s):

Olivia P. Damasco ◽

Mike K. Smith ◽

Ian D. Godwin ◽

Steve W. Adkins ◽

Robert M. Smillie ◽

...

Keyword(s):

Chlorophyll Fluorescence ◽

Low Temperature ◽

Flux Density ◽

Environmental Conditions ◽

Photon Flux ◽

Photon Flux Density ◽

Leaf Production ◽

Musa Spp

The responses of micropropagated normal plants and dwarf off-types of Cavendish (Musa spp. AAA) bananas to suboptimal temperatures were evaluated under field and controlled environmental conditions. Compared with bananas grown at 30/25°C (day/night), leaf production at 18/14°C was inhibited by 51% in normal plants and 18% in dwarf off-types. The emergence of the first leaf that developed at low temperature was delayed by 11 days for normal plants and 5 days for the dwarf off-types. Photoinhibition of lamina, measured by decrease in the chlorophyll fluorescence variable Fv/Fm, occurred in all banana plants growing in the field during the winter months. The extent to which the plants were photoinhibited was significantly greater for the normal plants than dwarf off-types. Under controlled environmental conditions, photoinhibition was similarly greater in normal plants than dwarf off-types. After 153 h at 18/14C and a 9-h photoperiod of photon flux density (PFD) of 380 mmol/m2· s, Fv/Fm was reduced by 22 and 13% for normal and dwarf off-types, respectively. When plants were exposed to 18°C and a continuous PFD of 380 µmol/m2· s for 20 h, Fv/Fm was reduced by 50% for normal plants and 36% for dwarf off-types. The results of the study indicate that dwarf off-types generated from banana micropropagation showed improved tolerance to low temperature and light, showing better growth and lower susceptibility to low-temperature induced photoinhibition than normal plants.

Download Full-text

Comparison of the Photoautotrophic Growth Regimens of Chlorella sorokiniana in a Photobioreactor for Enhanced Biomass Productivity

Biology ◽

10.3390/biology9070169 ◽

2020 ◽

Vol 9 (7) ◽

pp. 169

Author(s):

Elvira E. Ziganshina ◽

Svetlana S. Bulynina ◽

Ayrat M. Ziganshin

Keyword(s):

Large Scale ◽

Basal Medium ◽

Biomass Productivity ◽

Chlorella Sorokiniana ◽

Pigment Concentration ◽

Photon Flux ◽

Photon Flux Density ◽

Total Biomass ◽

Initial Growth ◽

Wide Range

Microalgae have a wide industrial potential because of their high metabolic diversity and plasticity. Selection of optimal cultivation methods is important to optimize multi-purpose microalgal biotechnologies. In this research, Chlorella sorokiniana AM-02 that was isolated from a freshwater lake was cultured under various high photosynthetic photon flux density (PPFD) conditions and CO2 gas levels in standard Bold’s basal medium (BBM). Furthermore, a wide range of nitrate levels (180–1440 mg L−1) was tested on the growth of C. sorokiniana. Microalgae growth, pigment concentration, medium pH, exit gas composition, as well as nitrate, phosphate, and sulfate levels were measured during an experimental period. The preferred high PPFD and optimal CO2 levels were found to be 1000–1400 μmol photons m−2 s−1 and 0.5–2.0% (v/v), respectively. The addition of nitrate ions (up to 1440 mg L−1) to the standard growth medium increased final optical density (OD750), cell count, pigment concentration, and total biomass yield but decreased the initial growth rate at high nitrate levels. Our findings can serve as the basis for a robust photoautotrophic cultivation system to maximize the productivity of large-scale microalgal cultures.

Download Full-text