Use of hydrogel in the irrigation management of white pitaya (Hylocereus undatus) seedlings: Biometrics and accumulation of organic and inorganic solutes

The initial development of pitayas may be limited by a few factors, among them, water deficit. Agricultural hydrogels can be used as an alternative to enhance the retention and availability of water and nutrients in the soil. Therefore, this study aimed to evaluate the influence of irrigation frequency and hydrogel doses on the development of white pitaya (Hylocereus undatus) seedlings to establish a time interval in days between irrigations that provides better seedling development and determine the hydrogel dose that provides a reduction of water consumption without damaging seedling development. The experimental design consisted of randomized blocks in a 4 x 4 factorial arrangement, in which the treatments corresponded to 4 hydrogel doses (0, 2, 4, and 6 g/plant of Biogel Hidro Plus) incorporated into the substrate and four irrigation frequencies (1, 3, 5, and 7 days of interval). The biometric characteristics, photosynthetic pigments, and organic and inorganic solutes of the plants were evaluated after 120 days. The use of daily irrigation negatively influenced the growth and biomass accumulation of the aerial part of the seedlings and, consequently, provided the lowest values of cladodes of the pitaya seedlings. Pitaya seedlings had greater development when using an irrigation frequency of around 3 days. The application of 6 g/plant of hydrogel provided the highest averages for accumulation of dry biomass, photosynthetic pigments, and organic and inorganic solutes at irrigation levels of 3.6, 4, and about 3.8 days of intervals, respectively. Hydrogel incorporation allowed increasing the interval between irrigations by 1 day without damages to the seedling development.

Gas exchanges and photosynthetic pigments of ‘Tommy Atkins’ mango as a function of fenpropimorph

ABSTRACT The objective of the present study was to evaluate the influence of the application of fenpropimorph and paclobutrazol on gas exchanges and photosynthetic pigments of ‘Tommy Atkins’ mango grown in the semi-arid region in different evaluation periods. Two experiments were carried out in ‘Tommy Atkins’ mango orchards in the first production cycle between September and December 2018 (first experiment) and between September and December 2019 (second experiment) in Petrolina, PE, Brazil. The experimental design adopted was randomized blocks in split plots in time, 4 × 4 + 1, with four replicates. The plots corresponded to the concentrations of fenpropimorph: 0, 0.7, 1.0, and 1.3 g per linear meter of plant canopy diameter plus the additional paclobutrazol treatment (1 g per linear meter of plant canopy diameter), and the subplots corresponded to the evaluation dates (0, 30, 60, and 90 days after the first application of treatments). The following traits were evaluated: CO2 assimilation rate, stomatal conductance, internal CO2 concentration, transpiration, water use efficiency, chlorophyll a, chlorophyll b, total chlorophyll, and carotenoids. The fenpropimorph dose of 1.3 g per linear meter of plant canopy promotes a higher rate of CO2 assimilation; however, paclobutrazol was more effective in the accumulation of chlorophyll a and total chlorophyll, and the use of fenpropimorph did not interfere in the concentration of photosynthetic pigments.

Complementary Approaches to Assess Phytoplankton Groups and Size Classes on a Long Transect in the Atlantic Ocean

Phytoplankton biomass, through its proxy, Chlorophyll a, has been assessed at synoptic temporal and spatial scales with satellite remote sensing (RS) for over two decades. Also, RS algorithms to monitor relative size classes abundance are widely used; however, differentiating functional types from RS, as well as the assessment of phytoplankton structure, in terms of carbon remains a challenge. Hence, the main motivation of this work it to discuss the links between size classes and phytoplankton groups, in order to foster the capability of assessing phytoplankton community structure and phytoplankton size fractionated carbon budgets. To accomplish our goal, we used data (on nutrients, photosynthetic pigments concentration and cell numbers per taxa) collected in surface samples along a transect on the Atlantic Ocean, during the 25th Atlantic Meridional Transect cruise (AMT25) between 50° N and 50° S, from nutrient-rich high latitudes to the oligotrophic gyres. We compared phytoplankton size classes from two methodological approaches: (i) using the concentration of diagnostic photosynthetic pigments, and assessing the abundance of the three size classes, micro-, nano-, and picoplankton, and (ii) identifying and enumerating phytoplankton taxa by microscopy or by flow cytometry, converting into carbon, and dividing the community into five size classes, according to their cell carbon content. The distribution of phytoplankton community in the different oceanographic regions is presented in terms of size classes, taxonomic groups and functional types, and discussed in relation to the environmental oceanographic conditions. The distribution of seven functional types along the transect showed the dominance of picoautotrophs in the Atlantic gyres and high biomass of diatoms and autotrophic dinoflagellates (ADinos) in higher northern and southern latitudes, where larger cells constituted the major component of the biomass. Total carbon ranged from 65 to 4 mg carbon m–3, at latitudes 45° S and 27° N, respectively. The pigment and cell carbon approaches gave good consistency for picoplankton and microplankton size classes, but nanoplankton size class was overestimated by the pigment-based approach. The limitation of enumerating methods to accurately resolve cells between 5 and 10 μm might be cause of this mismatch, and is highlighted as a knowledge gap. Finally, the three-component model of Brewin et al. was fitted to the Chlorophyll a (Chla) data and, for the first time, to the carbon data, to extract the biomass of three size classes of phytoplankton. The general pattern of the model fitted to the carbon data was in accordance with the fits to Chla data. The ratio of the parameter representing the asymptotic maximum biomass gave reasonable values for Carbon:Chla ratios, with an overall median of 112, but with higher values for picoplankton (170) than for combined pico-nanoplankton (36). The approach may be useful for inferring size-fractionated carbon from Earth Observation.

Towards a quantitative description of excitonic couplings in photosynthetic pigment-protein complexes: quantum chemistry driven multiscale approaches

A structure-based quantitative calculation of excitonic couplings between photosynthetic pigments has to describe the dynamical polarization of the protein/solvent environment of the pigments, giving rise to reaction field and screening...

EDTA and nitric acid responses on nickel uptake, translocation factor and pigments on Spinacia oleracea L. replanted seedlings in hydroponic solution

The effects of Na2EDTA and HNO3 on Ni2+ uptake by Spinacia oleracea seedlings replanted inhydroponic culture in a greenhouse was investigated. Eight week old seedlings, were exposed to various doses of Ni2+ (0, 1000, 2000, and 4000 mg/L) as NiSO4, at (0, 500 and 3000 mg/L) Na2EDTA and ( 0, 500 and 3000 mg /L) HNO3 in different combinations. There was a substantial increase in nickel uptake in chelated treatments (p < 0.05) compared to unchelated treatments of same concentrations of Ni2+. So, chelation enhanced Ni2+ uptake in S. oleracea. During the exposure, antioxidant defense system helped the plant to protect itself from the damage. Due to increasing nickel uptake by the plant, the photosynthetic pigments (i.e chlorophyll a, chlorophyll b and Caretenoids) gradually declined. In this study, Spinacia oleracea Seedlings and contents of the photosynthetic pigments (chlorophyll a, chlorophyll b and Caretenoids) of both chelated and unchelated hydroponic treatments were investigated. Changes in photosynthetic pigments was significant (p < 0.05) with respect to addition of EDTA and HNO3 at different concentration to different concentrations of Ni2+ compared to unchelated treatments of same concentrations of Ni2+. The Ni2+ induced translocation factor was also determined which increased significantly (P < 0.05) with increasing Ni2+ concentrations.

Biochemical characteristics of plant species of the genus Acer L.

The plants of the genus Acer section Palmata, which grow on the territory of M. M. Gryshko National Botanical Garden of NAS of Ukraine were investigated. It was found that the vast majority of A. palmatum and its cultivars were winter hardy. A study of the content of photosynthetic pigments revealed that the lowest content was in A. palmatum ‘Bloodgood’. The lowest content of malonic dialdehyde and proline was found in the leaves of A. palmatum ‘Dissectum’ and A. palmatum ‘Orange dream’, and the highest — in A. palmatum ‘Atropurpureum’ and A. palmatum. The greatest catalase activity was found in plants of A. palmatum ‘Atropurpureum’, and flavonoids — in A. palmatum.