Effects of Artificial Light Treatments on Growth, Mineral Composition, Physiology, and Pigment Concentration in Dieffenbachia maculata “Compacta” Plants

Specific wavebands may allow precise control of plant growth. However, light sources must be carefully evaluated before the large-scale use of supplemental light sources can be implemented. Dieffenbachia maculata “Compacta” plants were grown for 8 weeks in pots in a growth chamber under tightly controlled temperature and humidity in order to assess the effects of supplemental light. Three treatments were applied: (i) using 18-W fluorescent bulbs (T1), (ii) using the same bulbs with supplemental light emitting diodes (LEDs) (Pure Blue and Pure Red Mix-Light-Emitting Diodes (BR-LEDs)) (T2), and (iii) using high-efficiency TL5 fluorescents (T3). Plant biomass, mineral composition, and physiological and photosynthetic parameters were assessed under each light treatment. Total plant dry weight was highest in plants grown under treatments T1 and T3. Other differences were observed between different light treatments, including variation in biomass partitioning as well as N and K concentrations in roots, stems, and leaves. Further, proline and indole 3-acetic acid (IAA) levels were higher in plants grown under the T1 treatment, whereas total soluble sugars and starch were higher in plants grown under treatment T3. Plants grown under treatment T1 had the lowest chlorophyll concentrations. No differences were observed in organ water content and P concentration. T2 was not the best treatment, as expected. The model proposed a linear regression between integrated use of spectral energy (IUSE) and total dry weight (TDW), which showed a good relationship with an R2 value of 0.83. Therefore, we recommend this methodology to discern the effects of the different spectral qualities on plant biomass

Fittonia verschaffeltii Response to Artificial Light Treatments: BIOMASS, Nutrient Concentrations and Physiological Changes

The purpose of the present study was to evaluate the effects of different light treatments on biomass, nutrient concentrations and physiological parameters of Fittonia verschaffeltii (Lem) Van Houtte. The aim was to establish a methodology to evaluate the effect of photosynthetically active radiation (PAR) emitted by lamps on biomass. The light treatments used were tube luminescent Dunn (TL-D), tube luminescent Dunn + light emitting diodes (LEDs) and Tube luminescent 5 (TL-5). At the end of the experimental period, biomass, nutritional, biochemical, and physiological parameters were assessed. A clear reduction in total plant dry weight under TL-D + LEDs at the end of the experiment was recorded. With respect to nutrient concentration in the different organs assessed, there was no clear response under the different light treatments. The growth under TL-D lamps resulted in the highest concentration of total soluble sugars and starch in leaves, whereas the highest value of indole 3-acetic acid concentration was under TL-5 lamps. Plants grown under TL-D + LEDs showed the lowest values of chlorophyll a, b and a + b. The relationship proposed between integrated use of spectral energy (IUSE) and total dry weight (TDW) showed a good correlation with an R2 value of 0.86, therefore we recommend this methodology to discern the effects of the different spectral qualities on plant biomass

Fertigation Strategies to Alleviate Fertilizer Contamination Generated by Tomato Crops under Plastic Greenhouses

The rapid development of greenhouse horticulture has brought about a dramatic increase in the nitrate pollution of aquifers. The optimization of nitrogen application is an important tool to minimize nitrogen losses. The objective of this research was to assess the effect of different fertigation strategies, based on the reduction of the nitrogen applied and the use of a percentage of NH4+ as a nitrogen source, on the decrease in the environmental impact caused by the traditional system, as well as to evaluate if this is compatible with a high fruit yield (considering quantity and quality). Lycopersicum esculentum Mill cv. Forteza plants were grown in a polyethylene greenhouse. Tomato yield and quality were evaluated, along with leachates, which were collected by means of rigid plastic lysimeters. The proposed strategies did not reduce fruit yield. However, the reduction in the nitrate applied caused firmness and °Brix decrease, together with a diminution in titratable acidity until 124 days after transplanting. Nevertheless, these effects were not observed with the replacement of some of the NO3− by NH4+. The reduction in fertilizer inputs significantly improved water and nutrient (N, P and K) use efficiency. The treatment with NH4+ improved K use efficiency, compared to the conventional treatment, but P decreased. The highest NO3− and K leaching was detected in the traditional treatment

Comparative Behavior of Dracaena marginata Plants Integrated into a Cascade Cropping System with the Addition of Hydrogen Peroxide

The reuse of crop drainage into other crops, in the form of a cascade cropping system, is a feasible environmental solution where high inputs of water and fertilizer are used for crop growth and lower efficiency rates, associated with a high discharge of water and fertilizers into the environment, are present. Dracaena marginata plants were cultured in containers with sphagnum peat moss and were subjected to three different fertigation treatments for eight weeks: Dm0 (standard nutrient solution or control treatment), Dm1 (raw leachates), and Dm2 (raw leachates with additional H2O2), where the leachates were collected from a Chrysalidocarpus lutescens-Dracaena deremensis cascade cropping system. At the end of the harvesting, growth parameters, pigment concentration, leaf and root proline, total soluble sugar concentrations, and water and nutrient use efficiencies were assessed for each fertigation treatment. Plant height, root, stem, and total dry weight increased under fertigation with leachates with H2O2. The fertigation with leachates with or without H2O2 increased the red index value. There were no clear trends between the fertigation treatments with regards to pigment concentrations and biochemical parameters (proline and total soluble sugar concentrations). The addition of H2O2 to the leachate increased N concentration in the organs assessed, as well as the water and nutrient use efficiencies. There were no variations in H2PO4−, SO42−, Na+, and Mg2+ concentration in the chemical composition of the substrate between fertigation treatments. The positive results reported in this experiment suggest the potential growth of Dracaena marginata with leachate and hydrogen peroxide in a cascade cropping system

Water and Nutrient Balance in an Ornamental Cascade Cropping System

Seedlings of Chrysalidocarpus lutescens, Dracaena deremensis and Dracaena marginata were grown in plastic containers filled with sphagnum peat-moss to assess the effects of three different water systems on plant growth, water saving and nutrient removal during the experimental period. The experiment lasted for 8 weeks and consisted of three water systems. These consisted of an open draining system fertigated with a standard nutrient solution (system T0) and two closed systems: sequential reuse of the leachate (system T1) and sequential reuse of the leachate with the addition of H2O2 (system T2). Over the course of the experiment, samples of water and supplies generated in each water treatment were collected weekly, and from these data water volume and nutrient loads were calculated. The addition of H2O2 to the leachate resulted in an enhancement in plant dry weight in Dracaena deremensis and Dracaena marginata. Regarding anion loads (Cl−, NO3−, H2PO4−, SO42−) in these water systems, there was a removal rate of 42%, 28%, 27% and 28%, respectively, in the closed systems compared to the open system. For the cation loads (Na+, K+, Ca2+ and Mg2+) in these water systems, there was a removal rate from 28% to 29%, respectively, in the closed systems compared to the open syste

Phosphorus and Carbohydrate Metabolism in Green Bean Plants Subjected to Increasing Phosphorus Concentration in the Nutrient Solution

Phosphorus (P) is considered an elementary mineral nutrient for plants. Nevertheless, excessive or deficit supply to the crop may cause negative changes at the physiological level. Plants were cultivated in pots in a growth chamber under increasing P concentration (P1 (0.5 mmol/L (control treatment)), P2 (1 mmol/L); P3 (2 mmol/L); P4 (4 mmol/L); P5 (6 mmol/L), and P6 (8 mmol/L)) in the nutrient solution for 40 days. At the end of the experimental period, biomass, carbohydrates concentration, and enzymatic activities related to the synthesis and degradation of sucrose as well as the different fractions of P in different organs of the plant were assessed. The results obtained in this experiment reveal a decrease in biomass under increasing P supply. Fructose, glucose, sucrose, and starch concentrations were higher in the shoots compared to the roots. There were different trends in the roots and shoots in enzymatic activities related to sucrose. The increase in P dose increased the concentration of the different forms assessed for P in all the organs studied. Seed phytate concentration surpassed the threshold established by the Food and Agriculture Organization (FAO) for green bean plants grown under P4, P5, and P6 treatments. Considering the results obtained, we suggest fertigation with a concentration of 2 mmol/L to obtain a higher productivity without excess of phytate in seeds

Monitoring Optical Tool to Determine the Chlorophyll Concentration in Ornamental Plants

The accurate estimation of leaf photosynthetic pigments concentration is crucial to check the plant´s health. Traditional methods of measuring photosynthetic pigments involve complex procedures of solvent extraction followed by spectrophotometric determinations. Portable plant instruments such as Soil Plant Analysis Development (SPAD) meters can facilitate this task for the speed and simplicity of the measures. The relationship between chlorophyll index obtained by SPAD-502 and pigment concentration in several ornamental species can help in the management of ornamental plant production. Two trials have been carried out in two different growing seasons (spring and summer) and facilities (greenhouse and open air), involving 30 ornamental species. There was a high linear relationship between concentrations of Chla and Chlb, as well as between Chlt and Ct in different species studied under greenhouse and open field conditions. The ratio between Chla and Chlb was higher at open field conditions and similar between Chlt and Ct. There was also a good relationship between Chlorophyll index and Chlt under both growing conditions, as well as between Chlorophyll index and Ct under greenhouse conditions. However, linear relationships with different slopes were observed for groups of species at open field conditions

Physiological Responses of Tomato and Cucumber Seedlings under Different Light–Dark Cycles

Tomato and cucumber seedlings were grown in a growth chamber to evaluate the effects of different cycles of light–dark exposure conditions (T0 (control treatment) (1 cycle of 24 h distributed in 18 h of light exposure and six hours of dark), T1 (two cycles of 12 h distributed in nine hours of light exposure and three hours of dark) and T2 (three cycles of eight hours distributed in six hours of light exposure and two hours of dark) on growth, nutrient status, pigment concentration and physiological changes. Total dry weight showed different behaviors in both species, since in tomato the total dry weight remained unchanged under varying light–dark cycles, whereas in cucumber seedlings there was a clear decrease compared to the control treatment. In both species, plants grown under T2 showed the best water content. Nitrogen, P and K content—as well as partitioning in the different organs of the plants—displayed different patterns under varying cycles of light–dark conditions in both species. Chlorophyll (b and a + b) concentration decreased significantly in both species in T1 and T2 compared to the control treatment (T0). At physiological level, the concentration of total soluble sugars and proline in leaf showed the highest value in the control treatment with 18 h of light and six hours of dar

Effects of Fertigation with Untreated and Treated Leachates from Municipal Solid Waste on the Microelement Status and Biometric Parameters of Viola × wittrockiana

Landfill leachate can release pollutants into the environment. Nevertheless, it can be treated using a phytodepuration system via constructed wetlands to reduce contaminants. Moreover, this leachate can also increase the availability of macro and micronutrients in soil and water. In this trial, the reuse of untreated and treated wastewater from municipal solid waste (MSW) for fertigation was assessed. Plantlets of Viola × wittrockiana (pansy) were grown in a greenhouse and five fertigation treatments were applied: W9.0 (pure wastewater, EC 9.0 dS m−1), W4.5 (diluted wastewater, EC 4.5 dS m−1), DW4.5 (depurated wastewater, EC 4.5 dS m−1), PW4.5 (phytodepurated wastewater, EC 4.5 dS m−1), and T (tap water, control, EC 1.5 dS m−1). The treatment with untreated wastewater had a negative effect on plant dry weight, leaf size, specific leaf area, water content, and the number of closed and open flowers, due to the high concentration of SO42− in the fertigation water. It also reduced the content of Cu, Mn, Fe, and Zn with respect to the control, because of the dry biomass diminution. Conversely, fertigation with phytodepurated wastewater enhanced root and shoot dry weight, water content, and the number of closed and open flowers. Cu and Mn contents in flowers surpassed the content detected in plants fertigated with untreated leachates. These findings demonstrate that phytodepurated wastewater obtained from MSW can be employed for the fertigation of this species

Growth, Photosynthesis, and Physiological Responses of Ornamental Plants to Complementation with Monochromic or Mixed Red-Blue LEDs for Use in Indoor Environments

Inch (Tradescantia zebrina) and spider (Chlorophytum comosum) plants were grown in a growth chamber for two months in plastic containers to evaluate the effects of different light treatments (TO Tube luminescent Dunn (TLD) lamps or control), TB (TLD lamps + blue light emitting diodes (LEDs)), TR (TLD lamps + red LEDs), and TBR (TLD lamps + blue and red LEDs) on biomass, photosynthesis, and physiological parameters. Total dry weight and water content were evaluated at the end of the experimental period. After two months, pigment concentrations and the photosynthetic rate were assessed in both species. The total soluble sugar, starch, and proline concentrations in the leaf as physiological parameters were studied at the end of the experiment. Both species had increased root, shoot, and total dry weight under blue LEDs conditions. The chlorophyll concentration showed a specific response in each species under monochromic or mixed red-blue LEDs. The highest photosynthetic rate was measured under the addition of mixed red-blue LEDs with TLD lamps. At the physiological level, each species triggered different responses with respect to total soluble sugars and the proline concentration in leaves under monochromic or mixed red-blue LEDs. Our study demonstrated that the addition of blue LEDs is advisable for the production of these ornamental foliage species