Effects Of Photosynthetic Photon Flux Research Articles

Plant factories; crop transpiration and energy balance

Population growth and rapid urbanisation may result in a shortage of food supplies for cities in the foreseeable future. Research on closed plant production systems, such as plant factories, has attempted to offer perspectives for robust (urban) agricultural systems. Insight into the explicit role of plant processes in the total energy balance of these production systems is required to determine their potential. We describe a crop transpiration model that is able to determine the relation between sensible and latent heat exchange, as well as the corresponding vapour flux for the production of lettuce in closed systems. Subsequently, this model is validated for the effect of photosynthetic photon flux, cultivation area cover and air humidity on lettuce transpiration, using literature research and experiments. Results demonstrate that the transpiration rate was accurately simulated for the aforementioned effects. Thereafter we quantify and discuss the energy productivity of a standardised plant factory and illustrate the importance of transpiration as a design parameter for climatisation. Our model can provide a greater insight into the energetic expenditure and performance of closed systems. Consequently, it can provide a starting point for determining the viability and optimisation of plant factories.

Effects of photosynthetic photon flux and carbon dioxide concentration on the photosynthesis and growth of grafted pepper transplants during healing and acclimatization

In the production of grafted transplants, healing and acclimatization are the most critical processes for survival. We investigated the influence of the photosynthetic photon flux (PPF) and the carbon dioxide (CO2) concentration during healing and acclimatization on the photosynthetic characteristics and growth of grafted pepper transplants to determine the optimum environmental conditions for healing and acclimatization in a healing chamber with artificial lighting source. Grafted pepper transplants were healed and acclimatized under two levels of CO2 (374 or 1,013 μmol·mol−1) and four levels of PPF (dark, 50, 98 or 147 μmol·m−2·s−1) for six days. The CO2 exchange rates of the grafted pepper transplants significantly increased with increasing PPF during healing and acclimatization. The CO2 exchange rates were higher under elevated CO2 concentrations than ambient CO2 concentration. The effect of CO2 enrichment was greater in low light intensity. The CO2 exchange rates at 50, 98 or 147 μmol·m−2·s−1 under elevated CO2 concentrations were 511, 261, and 172%, respectively, compared to the ambient CO2 concentrations. The increase of photosynthesis led to an improvement in growth. The SPAD value, dry weight and leaf area were greater under higher PPF and CO2 concentrations. PPF also influenced the anatomical structures of the leaves, and the palisade and spongy tissue cells of the leaves irradiated with higher PPF were aligned more densely, with more chloroplasts and small empty space. When compared to the tunnel in the greenhouse with natural light, healing and acclimatization under high CO2 (1,000 μmol·mol−1) and PPF (150 μmol·m−2·s−1) conditions in the healing chamber promoted the growth and graft union formation of grafted pepper transplants. The results suggested that high-quality grafted pepper seedlings could be achieved by healing and acclimatization in a healing chamber where optimal conditions such as high PPF and CO2 were maintained within the range evaluated in this experiment.

A trial of production of the plant-derived high-value protein in a plant factory

One of the ultimate goals of plant science is to test a hypothesis obtained by basic science and to apply it to agriculture and industry. A plant factory is one of the ideal systems for this trial. Environmental factors affect both plant yield and the accumulation of recombinant proteins for industrial applications within transgenic plants. However, there have been few reports studying plant productivity for recombinant protein in closed cultivation systems called plant factories. To investigate the effects of photosynthetic photon flux (PPF) on tomato fruit yield and the accumulation of recombinant miraculin, a taste-modifying glycoprotein, in transgenic tomato fruits, plants were cultivated at various PPFs from 100 to 400 (µmol m-2 s-1) in a plant factory. Miraculin production per unit of energy used was highest at PPF100, although miraculin production per unit area was highest at PPF300. The commercial productivity of recombinant miraculin in transgenic tomato fruits largely depended on light conditions in the plant factory. Our trial will be useful to consider the trade-offs between the profits from production of high-value materials in plants and the costs of electricity.

Light Intensity and Fertilizer Concentration: I. Estimating Optimal Fertilizer Concentrations from Water-use Efficiency of Wax Begonia

Environmental conditions and incorporation of nutrients into the growing medium can affect the fertilizer needs of bedding plants. To evaluate the effects of photosynthetic photon flux (PPF) and starter fertilizer on the fertilizer requirements of subirrigated plants, we grew wax begonias (Begonia semperflorens-cultorum Hort.) under three PPF levels (averaging 4.4, 6.2, and 9.9 mol·m-2·d-1) and four fertilizer concentrations [electrical conductivity (EC) of 0.15, 0.33, 0.86, and 1.4 dS·m-1] in a normal (with starter fertilizer, EC = 2.1 dS·m-1) and heavily leached (with little starter fertilizer, EC = 0.9 dS·m-1) growing medium. Except for shoot dry mass, we did not find any significant interactions between PPF and fertilizer concentration on any of the growth parameters. There was an interactive effect of fertilizer concentration and starter fertilizer on all growth parameters (shoot dry mass, leaf area, plant height, and number of flowers). When the growing medium contained a starter fertilizer, fertilizer concentration had little effect on growth. When the growing medium was leached before transplanting, growth was best with a fertilizer EC of 0.86 or 1.4 dS·m-1. Water-use efficiency (WUE) was calculated from 24-hour carbon exchange and evapotranspiration measurements, and used to estimate the required [N] in the fertilizer solution to achieve a target tissue N concentration of 45 mg·g-1. Increasing PPF increased WUE and the required [N] (from 157 to 203 mg·L-1 at PPF levels of 4.4 and 9.9 mol·m-2·d-1, respectively). The PPF effect on the required [N] appeared to be too small to be of practical significance, since dry mass data did not confirm that plants grown at high light needed higher fertilizer concentrations. Thus, fertilizer concentrations need not be adjusted based on PPF.

Irradiance, Temperature, and Carbon Dioxide Enrichment Affect Photosynthesis in Phalaenopsis Hybrids

The short-term effects of photosynthetic photon flux (PPF), day/night temperatures and CO2 concentration on CO2 exchange were determined for two Phalaenopsis hybrids. At 20 °C, the saturating PPF for photosynthesis was 180 μmol·m-2s-1. At this PPF and ambient CO2 level (380 μL·L-1), a day/night temperature of 20/15 °C resulted in the largest daily CO2 uptake. Higher night temperatures probably increased the respiration rate and lowered daily CO2 uptake in comparison with 20/15 °C. An increase in the CO2 concentration from 380 to 950 μL·L-1 increased daily CO2 uptake by 82%.

Effects of Photosynthetic Photon Flux, Photoperiod, and CO2 Enrichment on the Growth and Morphogenesis of Lettuce Plug Transplants

Artificial lighting is widely used in controlled environment plant production to enhance plant growth and quality. However, high light intensity with artificial lighting is costly, and often causes increase of leaf temperature and, thus, leaf burn. We investigated the effects of photosynthetic photon flux (PPF) and photoperiod on the growth and morphogenesis of lettuce plug transplants under ambient and enriched CO2 levels. Three days after seeding, the plants were cultured under four PPF levels (100, 150, 200, and 300 μmol·m–2·s–1), two photoperiods (16 and 24 hr), and two CO2 levels (400 and 800 μmol·mol–1) for 18 days in growth chambers. Light source was fluorescent lamps. The air temperature around the plants was kept at 20°C. The results showed that dry weight of the plants increased linearly as PPF and daily integrated PPF (product of PPF and photoperiod) increased under both CO2 levels. At the same daily integrated PPF, higher CO2 level and longer photoperiod led to higher dry weight of the plants. CO2 enrichment increased significantly dry weight of the plants. The ratio of T/R and specific leaf area of the plants decreased quadratically as daily integrated PPF increased under both CO2 levels. The ratio of leaf length to leaf width of the plants decreased quadratically as PPF increased under the two photoperiods and CO2 levels.

Branching of Chrysanthemum Cultivars Varies with Season, Temperature, and Photosynthetic Photon Flux

Effects of photosynthetic photon flux (PPF) and temperature on quantitative axillary budbreak and elongation of pinched chrysanthemum [Dendranthema ×grandiflorum (Ramat.) Kitamura] plants were studied in three experiments. In Expt. 1, 12 commercial cultivars were compared under fall and spring environmental conditions. Spring increases in lateral shoot counts were attributable to increased PPF and air temperature. Cultivars varied from 0 to 12 lateral branches per pinched plant and by as much as 60% between seasons. There was a linear relationship between lateral branches >5 cm at 3 weeks after pinching and final branch count (y = 0.407 + 0.914(x), r2 = 0.92). In Expt. 2, air was at 20 or 25C and the root zone was maintained at 5, 0, or –5C relative to air temperature. With air at 20C, lateral branch counts (3 weeks after pinch) declined by ≤50% with the medium at 15C relative to 25C. At 25C, lateral branch count was lower with medium at 30C than at 20C. Cultivars differed in their response to the treatments. Experiment 3 compared the interactions among temperature, PPF, and cultivar on lateral branch count. Depending on cultivar, the count increased the higher the PPF between 400 and 1400 μmol·m–2·s–1. Air temperature had no effect on lateral branch count. PPF had a stronger effect on lateral branch count than air temperature, and cultivars differed in their response.

Photosynthesis of meadowfoam leaves at various photon fluxes and CO 2 concentrations

Meadowfoam ( Limnanthes alba Hartweg ex Benth.) is a new oilseed crop. Information regarding the effects of photosynthetic photon flux (PPF) and carbon dioxide concentration [CO 2] on net photosynthesis is important for understanding the potential capacity and the limitations of this crop to assimilate CO 2. Such information is useful for further improvement of meadowfoam seed and oil yield, as well as for growing this plant in controlled environments. The steady-state CO 2 exchange rates (CER; leaf area basis) of Mermaid meadowfoam ( L. alba subsp. alba) leaves were measured in a semi-closed compensating system at various PPF and [CO 2]. Measurements were made on rosette leaves of controlled environment-grown plants during vegetative growth, early stem elongation and early flowering. At all stages of development, CER responded hyperbolically to PPF and reached near saturation at a PPF of about 900 μmol m −2 s −1 when [CO 2] was 340 μl l −1. At saturating PPF, leaf CER was 18 μmol m −2 s −1 during the vegetative stage, 15 μmol m −2 s −1 at early stem elongation and 8 μmol m −2 s −1 at early flowering. The apparent quantum yield (mole CER per mole PPF at leaf surface) determined at low PPF when the response curve was linear was the same during vegetative and early stem elongation. The 99% confidence intervals for the apparent quantum yield of these plants were 0.038 and 0.046. The 99% confidence intervals for light compensation point during these stages were 63 and 79 μmol m −2 s −1. During both vegetative and early stem elongation stages, the CER increased sharply as [CO 2] increased (PPF=1200 μmol m −2 s −1) and reached a plateau near 650 μl l −1 CO 2. At this saturating [CO 2], the CER was 45 μmol m −2 s −1 during the vegetative stage and 33 μmol m −2 s −1 during early stem elongation. The [CO 2] compensation point measured transiently on four plants during vegetative stage was 74±5 μl l −1. The photosynthetic rate and efficiency of L. alba were similar to those for cool-season C 3 grasses.

EFFECTS OF PHOTOPERIODS ON GREENHOUSE TOMATO AND PEPPER PRODUCTION

Most works on artificial lighting of winter greenhouse vegetable crops studied the effects of photosynthetic photon flux but rarely photoperiod. Over the last three years, we conducted experiments to find out the best photoperiods for production of greenhouse tomato and pepper. We found that extending photoperiod up to 20 hrs increased productivity of pepper plants while continuous light (24 hrs) decreased yields. For tomato plants, productivity reached a maximum under a 14-hr photoperiod while longer photoperiods (16 to 24 hrs) did not increase yields. For both pepper and tomato plants, optimal growth (shoot fresh and dry weights) was obtained under the same photoperiods that gave the best productivities. We also observed leaf chloroses on tomato plants after 6 weeks under photoperiods of 20 and 24 hrs and leaf deformations (wrinkles) on pepper plants exposed to continuous lighting. We also observed that plants under continuous light grew better and flowered earlier during the first 5 to 7 weeks of treatments. So, tomato and pepper plants can use advantageously continuous supplemental lighting for a short period of time but are negatively affected on a long term basis. Future works should look at varying photoperiods to optimize yields.

Temperature and Photosynthetic Photon Flux Influence Chrysanthemum Shoot Development and Flower Initiation under Short-day Conditions

Abstract The effects of photosynthetic photon flux (PPF), day temperature (DT) and night temperature (NT) on leaf number, leaf unfolding rate and shoot length were determined for chrysanthemum (Dendranthema grandiflora Tzvelev. ‘Bright Golden Anne’) grown under short day (SD) conditions. A functional relationship was first developed to predict if flower bud appearance would occur within 100 SD under a given set of environmental conditions. All combinations of DT and NT in the range from 10° to 30°C were predicted to result in flower bud appearance at higher PPF than 10.8 mol·day−1·m−2. The number of leaves formed below the flower increased quadratically as DT and/or NT increased from 10° to 30°. As PPF increased from 1.8 to 21.6 mol·day−1·m−2, one to two fewer leaves were formed per shoot. Rate of leaf unfolding increased linearly with increasing average daily temperature from 0.2 leaves/day at 10° to 0.5 leaves/day at 30°. Internode length was highly correlated with the difference between DT and NT (DIF = DT – NT) such that increasing DIF from –12° to 12° resulted in progressively longer internodes.