Chitosan Nanoparticles as Biostimulant in Lettuce (Lactuca sativa L.) Plants

Biodegradable nanoparticles such as chitosan nanoparticles (CSNPs) are used in sustainable agriculture since theyavoid damage to the environment;CSNPs have positive effects such as the accumulation of bioactive compoundsand increased productivity in plants. This study aimed to investigate the impact of applying CSNPs on lettuce,specifically focusing on enzymatic activity, bioactive compounds, and yield. The trial was conducted using a completelyrandomized design, incorporating CSNPs: 0, 0.05, 0.1, 0.2, 0.4, and 0.8 mg mL−1. The doses of 0.4 mg mL−1improve yields up to 24.6% increases and 0.1 mg mL−1 of CSNPs increases total phenols by 31.2% and antioxidantcapacity by 34.6%. In addition, when low concentrations of CSNPs (0.05 and 0.1 mg L−1) were applied, anincrease in catalase was determined. The CSNPs represent a good alternative to be used as a biostimulant in sustainableagriculture because they improve the yield and quality of lettuce by increasing the bioactive compounds.

Development of a Rapid and Efficient Liquid Chromatography Method for Determination of Gibberellin A4 in Plant Tissue, with Solid Phase Extraction for Purification and Quantification

A new, rapid and efficient reverse phase Liquid Chromatography (RP-LC) method was developed for determination of Gibberellin A4 (GA4) in samples of flower stalk of Dasylirion cedrosanum and vegetative tissue of Epithelantha micromeris. Purification of GA4 was carried out by solid phase extraction (SPE), in Epithelantha micromeris. In the chromatography method was obtaining a retention time of 2.1 min, using Hypersil GOLD C-18 column (100 × 4.6 mm dim and size particle 5 μ), mobile phase 50/50 acetonitrile/water and a flow 1.0 ml/min. Detection was carried out by a UV detector set at 205 nm, and a quantization limit of 0.4 mg/L. The obtained correlation coefficient was 0.995.

Dynamic modeling of mineral contents in greenhouse tomato crop

Tomato is one the most important vegetables worldwide and mineral nutrition in tomato crops is considered as the second most important factor in crop management after water availability. Mathematical modeling techniques allow us to design strategies for nutrition management. In order to generate the necessary information to validate and calibrate a dynamic growth model, two tomato crop cycles were developed. Several mineral analyses were performed during crop development to determine the behavior of N, P, K, Ca, Mg and S in different organs of the plant. Regression models were generated to mimic the behavior of minerals in tomato plants and they were included in the model in order to simulate their dynamic behavior. The results of this experiments showed that the growth model adequately simulates leaf and fruit weight (EF > 0.95 and Index > 0.95). As for harvested fruits and harvested leaves, the simulation was less efficient (EF < 0.90 and Index < 0.90). Simulation of minerals was suitable for N, P, K and S as both, the EF and the Index, had higher values than 0.95. In the case of Ca and Mg, simulations showed indices below 0.90. These models can be used for planning crop management and to design more appropriate fertilization strategies.

Effect of the Application of Produced Water on the Growth, the Concentration of Minerals and Toxic Compounds in Tomato under Greenhouse

During the production of petroleum and gas a by-product, known as congenital water, is obtained, which varies in composition depending on the geological formation from which it is extracted. In the industrial process its composition is modified and then it is known as “produced water”. These waters can contain high concentrations of mineral salts that can potentially be used for crop fertilization. The aim of this study was to evaluate the effects of the application of produced water on the mineral contents of the plants and levels of BTEX and TPH in the fruits of greenhouse tomato cultivation. The produced waters used were derived from gas producing zone of Sabinas-Piedras Negras in northern Mexico. These waters were analyzed according to NOM-143-SEMARNAT-2003. Waters from three different stations, (Buena Suerte, Forasteros and Monclova 1), were mixed with fresh water to obtain the treatment waters used. As a control, we used a complete Steiner solution. The results showed that the produced waters modified the absorption of essential minerals in tomato plants;it was observed that the mineral concentration in plant tissues was highest in the control plants, except for Na, in which the plants irrigated with produced water had the highest concentrations. The treatments with produced waters also affected negatively the root length, leaf dry weight, stem dry weight, number of fruits per plant, and the dry weight of the fruits.

Impact of ZnSO_(4)^(-)and ZnO Nanoparticles on Seed Germination and Seedling Growth of Lettuce

Micronutrient nanoparticles(NPs)are currently an option for chemical fertilization and biostimulation in crops.However,there is little information on the phytotoxic or biostimulatory effects of NPs at low concentrations of some elements,such as Zn.In this study,the effect of low concentrations of Zn oxide(ZnO)NPs on germination,growth variables,and nutritional attributes of lettuce(Lactuca sativa L.)was evaluated in comparison to Zn sulfate.Romaine lettuce seeds were treated with ZnSO_(4)^(-)×7H_(2)O and ZnO NPs at Zn molar concentrations of 1×10^(−3),5×10^(−3),1×10^(−4),5×10^(−4),1×10^(−5),5×10^(−5),1×10^(−6),and 5×10^(−6).The seeds treated with ZnSO4−at 5×10^(−6)registered the highest radicle length,73%more than the control treatment.The seeds treated with ZnSO4−at 5×10^(−3)registered the lowest values,with 50%less than the control treatment.ZnO NPs at 5×10^(−6)significantly increased content of chlorophyll A and B and total phenolics.These results indicate the possible existence of a mechanism related to the intrinsic nanoparticle properties,especially at low concentrations.

Concentration of Salicylic Acid in Tomato Leaves after Foliar Aspersions of This Compound

Increased plant tolerance to stress may be chemically induced with applications of salicylic acid (SA). The aim of this study was to determine the change in the SA leaf concentration over time in response to the SA spraying in leaves of greenhouse grown tomato. In sprayed leaves the SA concentration showed changes over time similar to the reported responses to environmental stress. Two days after the first application, the SA foliar concentration reached the maximum of 8 μg·g-1, equivalent to twice the amount observed in the control plants. SA decreased until it reached the level of control plants eight days later. A second application showed actually the same response, but with a faster decline of SA in two days. According to the results of this assay, SA applications on tomato should be performed within a minimum interval of eight days in order to maintain the SA concentration related with the increase in plant tolerance to environmental stress.

Application of two forms of silicon and their impact on the postharvest and the content of bioactive compounds in cucumber(Cucumis sativus L.)fruits

The metabolic activity of the fruits continues even after harvest,which results in the loss of bioactive compounds,a decrease in the quality of the fruits,softening and browning,among other negative effects.The use of certain elements such as silicon can improve postharvest quality,since it is involved in the metabolic,physiological and structural activity of plants,moreover can increase the quality of the fruits.In addition,nanotechnology has had a positive impact on crop yield,nutritional value,fruit quality and can improve antioxidant activity.For these reasons,the use of beneficial elements such as silicon in the form of nanoparticles can be a viable option to improve the characteristics of the fruits.In the present study was evaluated the application of potassium silicate(125,250 and 500 mg L^(−1))and SiO_(2) nanoparticles(125,250 and 500 mg L^(−1))during the development of the crop.The results showed that the application of silicon(potassium silicate and silicon nanoparticles)increased the content of total soluble solids(up to 15.6%higher than control),titratable acidity(up to 38.8%higher than control),vitamin C(up to 78.2%higher than control),phenols(up to 22%higher than control),flavonoids(up to 64.6%higher than control),and antioxidant activity in lipophilic compounds(up to 56.2%higher than control).This study suggests that the use of silicon can be a good option to increase the content of bioactive compounds in cucumber fruits when they are applied during the development of the crop.

Entire Whitening of Apple Trees to Increase Chill Units in Regions of Warm Temperatures during the Fall-Winter Seasons

Different studies have shown that global warming and climate change have increased the planet’s temperature in different locations. For the apple-growing farmers, this may have a negative impact on the accumulations of chill units when the air temperature during the fall-winter season increases. When the entire trees are covered with a reflective material, the wood temperature may decrease. Therefore, the objective of this study was to evaluate the effect of whitening (with calcium hydroxide) the entire apple trees (Malus domestica Borkh) after defoliation, on the branches and trunks’ internal temperature (under the bark), the accumulation of chill units (CU), its effects on fruit yield and quality and the relation with the use of thidiazuron (TDZ) (inducer of budbreak). The study was conducted during the fall-winter seasons of 2019-2020 and 2020-2021. The results of this study showed that at the hours of the highest incidence of solar radiation, the internal temperature of the whitened trunks and leaves decreases up to 9&deg;C and 6&deg;C respectively. The accumulated CU during the time of the study, of the whitened branches were up to 81% higher than the ones recorded on the branches with no whitening;while the CU was lost at the hours of highest solar radiation (due to a high temperature) were up to 37.2% smaller. Entire tree whitening increased up to 26% of the yield per tree compared to the application of TDZ. No statistical difference in fruit quality was observed between whitened trees and those with no whitening but with the application of thidiazuron.

Breaking Dormancy of “Tupy” Blackberry in Subtropical Conditions

In subtropical or tropical conditions, the insufficient winter chill accumulation is often a limiting factor to break the dormancy of temperate-climate species such as the blackberry, which requires using products to help break dormancy. This study evaluates the efficacy of compounds in breaking dormancy of blackberry and its consequent influence on phenology and crop yields. The experiment was conducted in S?o Manuel, State of S?o Paulo, Brazil, in the 2011/2012 production cycle. The plants used were two-year-old “Tupy” blackberry (Rubus spp.), with 0.6 × 4.0 m spacing (4.166 plants·ha-1). Pruning was performed in August, followed by the application of these treatments: control (water);hydrogen cyanamide (Dormex?);nitrogen fertilizer (Erger?) and mineral oil (Assist?). The concentrations of each compound used were: 2.0%, 4.0%, 6.0% and 8.0%. The compounds used influenced the budding, flowering and fruit harvest stages, in addition to providing increased yields depending on the concentration used. For hydrogen cyanamide the recommended concentration is of 4.2% and 5.4% for nitrogen fertilizer;doses above these concentrations may cause phytotoxic effects. For mineral oil the dose recommended is of 8.0%.

Fruit Set in Orange with Phytohormones and Its Relation to Endogenous Levels of GA3

This research work aims to contribute in increasing the fruit set in citrus, given its importance in determining fruit yield. The authors evaluated the effects of phytohormones （auxins, gibberellins and cytokinins） in the mooring and features of orange fruit in cultivars Washington navel and Thomson （Citrus sinensis （L.） Osb.）, The experiment was established in a split plot randomized complete block design with five treatments and four replications. Flower tissue samples were stored in liquid N until the extraction of gibberellins and the identification and quantification of GA3. The results showed statistically significant difference （P 〈 0.05） between treatments in the number of fruits retained 129 d after flowering and the percentage of final tie. GA3 content ranged, on a dry weight basis, from 1.66 mg＇g1 in the control to 20.79 mg.g-1 in the high dose. The mean dose （32.2 mg.L-1 auxins, gibberellins 32.2 mg L-1 and 83.2 mg.L-1 cytokinins） caused the largest increase in fruit set.

Phenolic Compounds Influence Seed Dormancy of Palicourea rigida H.B.K.(Rubiaceae),a Medicinal Plant of the Brazilian Savannah

Palicourea rigida H.B.K. (Rubiaceae), a medicinal species commonly known as douradinha, has wide distribution across ecosystems in Central and South America. This species exhibits seed dormancy delaying germination until optimal conditions for seedling growth and development are in place. While dormancy ensures species survival, it also presents a technical problem for developing P. rigida’s plant production program. Thus, the objective of this study was to investigate if secondary metabolites present in seeds influence the seed dormancy of P. rigida. Mature fruits were harvested from the native habitat, in the savanna region of the State of Minas Gerais during February 2009, 2010 and 2011. The content of phenolic compounds in the seed of P. rigida was measured, and the allelopathic effects were assessed using the germination of lettuces as model to detect phytotoxicity. The P. rigida seeds geminated at rates varying between 7% and 31% with a Seed Germination Index (SGI) of 0.09. Data suggest that the phenolic compounds present in the seeds may be responsible for seed dormancy.