Evaristo Mauro de Castro

Maize grown in the Brazilian second-crop (“safrinha”) season is frequently exposed to water limitation during grain filling, and seed treatment has been proposed to improve crop performance under such conditions. We evaluated seed treatment with a formulated product containing the elicitor protein HrpNEA (40 µg of formulated product seed⁻¹; 1% αβ harpin protein) in maize (hybrid DKB 390 PRO) grown under rainfed, drought-prone field conditions in a randomized complete block design, assessing 18 agronomic, physiological and biochemical traits spanning stand establishment, biomass partitioning, nitrogen metabolism, antioxidant responses, root system architecture and yield components. HrpNEA seed treatment was associated with a higher plant stand, greater root and shoot biomass and allocation to roots, higher nitrate reductase activity and leaf chlorophyll, increased superoxide dismutase and peroxidase activities, lower soluble protein and lipid peroxidation, and greater root length and surface area. With no change in kernel number, individual kernel weight and grain yield were 21.7% higher in treated plants. Thirteen of the 18 traits remained significant after false-discovery-rate correction; treated and control plots separated completely along the first principal component (57% of variance; exact within-block permutation test, P = 0.031), and all six physiological modules responded in a coordinated manner dominated by nitrate reductase activity, root length, biomass and antioxidant enzyme activity. A multiplicative decomposition of the yield response showed that kernel weight accounted for essentially the whole yield gain, whereas the higher stand was offset by an unmeasured compensatory factor, indicating that enhanced grain filling was the principal contributor. This systems-level covariation does not, however, establish the causal contribution of individual processes to yield, which could not be determined in this single-environment study.

The cultivation of pitahaya (Selenicereus undatus) has attracted increasing interest due to its hardiness, early fruiting, economic value, and medicinal potential. However, low propagation rates remain a limitation for commercial-scale production. This study aimed to evaluate the effects of different spectral light qualities (white, blue, purple and red LEDs) and zinc (Zn) concentrations (8.60 and 17.20 mg·L-1) on the growth, pigment content, anatomy, and Zn deposition in S. undatus cladodes in vitro. Biometric parameters, photosynthetic pigments, anatomical features, and energy-dispersive X-ray spectroscopy analysis were assessed. White and purple lights, combined with 8.60 mg·L-1 Zn, led to greater shoot length and higher fresh and dry mass of roots and shoots. White light also increased total chlorophyll content at both Zn concentrations. The number of vascular bundles increased with 17.20 mg·L-1 Zn, especially under purple light. The largest cladode cross-sectional area was observed under red light with high Zn concentration. Zn accumulation was low, with slightly higher atomic percentages in central ribs (0.30%) and at the margins (0.77%) under white light and high Zn concentration treatment, suggesting limited translocation and possible compartmentalization in vacuoles or apoplastic spaces. Stomatal density appeared to be modulated by both factors, increasing under red light and decreasing under blue light, depending on Zn concentration. Overall, white and purple LED lights with 8.60 mg·L-1 Zn optimized S. undatus growth and pigmentation in vitro. These findings enable improved micropropagation protocols for commercial production and potential biofortification strategies.

The micropropagation of dragon fruit (Selenicereus undatus) is an alternative method to produce vigorous plants with high phytosanitary quality. However, depending on the consistency of the growing medium (liquid, semi-solid, and solid), plants can develop physiological and anatomical disorders, impairing their growth and reducing their viability ex vitro. The aim of this study was to evaluate the biometric characteristics, photosynthetic pigments, and anatomical sections of S. undatus plants grown in five concentrations of agar (0.0, 3.5, 7.0, 10.5, and 14.0 g L^-1) in MS medium. Biometric characteristics (number of roots, length of the aerial part, and fresh and dry masses of the roots and aerial part of the plants), photosynthetic pigments (chlorophyll a, b, total and carotenoid contents), and anatomy [number of vascular bundles, cross-sectional area (mm²), and length of reserve parenchyma (μm)] were evaluated. Biometric, photosynthetic pigment, and anatomical characteristics differed between S. undatus plants for the different concentrations of agar. Plants grown in agar-free medium showed increased length, aerial and root biomass, indicating enhanced growth. In contrast, plants grown on media containing 10.5 g L^-¹ and 14.0 g L^-¹ agar exhibited higher levels of chlorophyll a, chlorophyll b, and total chlorophyll. Additionally, carotenoid levels were higher in plants grown on agar, regardless of concentration. Plants grown without agar showed higher vascular bundle count, cross-sectional area, and reserve parenchyma length than those with agar. In this way, S. undatus plants can be micropropagated efficiently in an agar-free medium.

This study aimed to evaluate the emergence, early growth, and anatomy of Schinus terebinthifolia Raddi cultivated in iron mining tailings. The seeds were obtained from trees used in urban afforestation and cultivated on two substrates: sand and iron mining tailings. The chemical composition of the mining tailing was characterized. The experiment was conducted in a growth room for 60 days. The emergence rate, seedling survival, height, number of leaves, chlorophyll content, and leaf and root anatomy were evaluated. The analysis of the composition of the mining tailings indicated that macro- and micronutrients were present, as well as potentially toxic elements such as Al, Cd, Cr, and Pb. The mining tailings reduced the emergence rate, and 25% of the seedlings died in this substrate. In addition, the mining tailings promoted a significant reduction in all parameters investigated, including seedling height, number of leaves, chlorophyll content, total leaf thickness, abaxial and adaxial epidermis thickness, palisade parenchyma thickness, and the length and width of the seeds. Additionally, the chloroplasts, the metaxylem vessel diameter, and the phloem proportion were evaluated. Interestingly, the tailings promoted an increase in the secretory channel. In the roots, no significant changes were observed in the parameters analyzed. Thus, the seeds of S. terebinthifolia germinated in the iron mining tailings, and 75% of the seedlings survived, showing their potential for reforestation. Nonetheless, iron mining tailings exhibited toxicity to S. terebinthifolia seedlings, reducing their photosynthetic tissues and, consequently, their growth; this toxicity is likely related to potentially toxic elements present in tailings.

Cadmium (Cd) is a heavy metal that is highly toxic to plants and animals and can accumulate in the environment as a result of industrial activities and agricultural application of some types of phosphate fertilizer. This study aimed to assess the role of sodium nitroprusside (SNP), as a source of nitric oxide (NO) in alleviating Cd stress in maize plants. Maize plants were kept in soil saturated with 40%-strength nutrient solution in a greenhouse, and cadmium nitrate, Cd(NO₃)₂, was applied at different concentrations, (0, 10, and 50 µM). Sodium nitroprusside, [Fe(CN)₅NO]·2H₂O, at concentrations of 0.05, 0.1, and 0.2 µM. Growth, leaf gas exchange, and leaf anatomy analyses were performed. The experimental design was completely randomized in a 3 × 3 factorial arrangement with five replicates. The highest concentrations of Cd and SNP reduced the total dry mass and leaf and stem dry mass but increased the allocation of biomass to the roots and stem, but the leaf allocation did not change. The application of Cd and SNP promoted an increase in gas exchange and leaf area, in addition to an increase in leaf tissue thickness and stomatal density. The presence of SNP at low concentrations reduces the toxicity of Cd, but at high concentrations, this compound can generate negative effects and even toxicity in maize plants.

Rare earth elements (REEs) have been intentionally used in Chinese agriculture since the 1980s to improve crop yields. Around the world, REEs are also involuntarily applied to soils through phosphate fertilizers. These elements are known to alleviate damage in plants under abiotic stresses, yet there is no information on how these elements act in the physiology of plants. The REE mode of action falls within the scope of the hormesis effect, with low-dose stimulation and high-dose adverse reactions. This study aimed to verify how REEs affect rice plants’ physiology to test the threshold dose at which REEs could act as biostimulants in these plants. In experiment 1, 0.411 kg ha⁻¹ (foliar application) of a mixture of REE (containing 41.38% Ce, 23.95% La, 13.58% Pr, and 4.32% Nd) was applied, as well as two products containing 41.38% Ce and 23.95% La separately. The characteristics of chlorophyll a fluorescence, gas exchanges, SPAD index, and biomass (pot conditions) were evaluated. For experiment 2, increasing rates of the REE mix (0, 0.1, 0.225, 0.5, and 1 kg ha⁻¹) (field conditions) were used to study their effect on rice grain yield and nutrient concentration of rice leaves. Adding REEs to plants increased biomass production (23% with Ce, 31% with La, and 63% with REE Mix application) due to improved photosynthetic rate (8% with Ce, 15% with La, and 27% with REE mix), favored by the higher electronic flow (photosynthetic electron transport chain) (increase of 17%) and by the higher F_v/F_m (increase of 14%) and quantum yield of photosystem II (increase of 20% with Ce and La, and 29% with REE Mix), as well as by increased stomatal conductance (increase of 36%) and SPAD index (increase of 10% with Ce, 12% with La, and 15% with REE mix). Moreover, adding REEs potentiated the photosynthetic process by increasing rice leaves’ N, Mg, K, and Mn concentrations (24–46%). The dose for the higher rice grain yield (an increase of 113%) was estimated for the REE mix at 0.72 kg ha⁻¹.

O objetivo deste trabalho foi descrever a morfologia de Merremia tomentosa. Os frutos foram coletados na Serra do Macaia, município de Lavras – MG, no período de fevereiro de 2007 a abril de 2008 e foram conduzidos ao Laboratório de Crescimento e Desenvolvimento de Plantas do Departamento de Biologia da UFLA/MG (Universidade Federal de Lavras – Minas Gerais), onde foram colocadas para germina, utilizando uma câmera de germinação tipo BOD com temperatura de 25ºC, 100% de UR e fotoperíodo de 12 horas. Foram descritos os aspectos morfológicos da planta na fase adulta, da germinação da semente e do desenvolvimento da plântula com 10, 16 e 30 dias. Da planta adulta descreveu-se morfologicamente o hábito, o caule, as folhas, a flor, a bráctea, a corola, as pétalas, o cálice, as sépalas, o androceu, os estames, o gineceu, os carpelos, o fruto e as sementes. A espécie é um subarbusto de caule ereto, cilíndrico; folhas simples, peninérveas, flores solitárias, axilares, pentâmeras; bráctea reduzida com protuberâncias; cálice dialissépalo, pentâmero; corola gamopétala, pentâmera de coloração branca; androceu com cinco estames; gineceu bicarpelar, de ovário súpero, bilocular, de estilete terminal, com dois estigmas fundidos subglobosos; fruto tipo cápsula de coloração que varia de castanho-pardo a castanho avermelhado quando maduros de deiscência tardia e irregular; sementes de coloração preta, embrião com dois cotilédones foliáceos, verdes e dobrados em labirinto. A germinação é epígea. A radícula rompe o tegumento no terceiro dia após a semeadura, caracterizando o início da germinação. Através das características morfológicas, é possível juntamente com as ilustrações, a identificação da espécie em seu ambiente natural, assim como o auxílio em análises laboratoriais.

Seasonally Dry Tropical Forests experience pronounced precipitation seasonality, intense solar radiation, and high temperatures, which often translate into high levels of deciduousness during the dry season. In these environments, deciduous species coexist with some evergreen species that are able to maintain their canopy leaves throughout the dry season. To understand the strategies behind this behavior, we analyzed leaf anatomical traits of 13 individuals of Sarcomphalus joazeiro during both the wet and dry seasons in a seasonal deciduous forest. We hypothesized that wet-season leaves would differ anatomically and functionally from dry-season leaves. Specifically, we expected wet-season leaves to show a more acquisitive resource-use strategy compared to dry-season leaves, which we expected to be more conservative. We assessed the effects of season and climatic variables on 25 leaf anatomical traits using generalized linear mixed models (LMM). Leaf traits varied between the wet and dry seasons and interacted with climatic variables, which together suggest that S. joazeiro produces season-specific leaf cohorts. This adaptation allows the species to adjust to the contrasting conditions of light intensity, temperature, and evaporative demand in each season.

The objective of this work was to evaluate the physiological and anatomical characteristics of garlic cultivar leaves that indicate tolerance or susceptibility to environmental factors. The experiment was conducted in a greenhouse in a completely randomized design, with eight treatments (cultivars). The evaluated cultivars were Amarantes, BRS Hozan, Caçador, Crespo, Chinês Folha Fina, Chonan, Gigante Roxo Escuro, and Ito. The following physiological variables were evaluated: net photosynthetic rate, stomatal conductance to water vapor, transpiration, internal and external carbon, and water use efficiency. The anatomical characteristics were analyzed with a microscope coupled to a camera. The Chinês Folha Fina, Chonan, Gigante Roxo Escuro, and Crespo cultivars showed higher mean photosynthetic rates and thicker photosynthetic tissues than the others. The Chonan and Crespo cultivars stood out for their higher photosynthetic rates, higher stomatal indices, thicker cuticle and epidermis, and larger mesophyll intercellular spaces, which are characteristics common to plants tolerant to water deficit. The characteristics of the Chonan and Crespo garlic cultivars are related to drought tolerance, and those of BRS Hozan, Ito, and Caçador to susceptibility.

The aim of this study was to evaluate the effect of light on anatomy, physiology and essential oil content and composition of Varronia curassavica. They were analysed two light conditions (full sunlight and protected environment with 50% shade screen) and five accessions (VCUR-101, VCUR-102, VCUR-201, VCUR-302, VCUR-802). V. curassavicacultivated in full sun presented a greater development of the leaf blade and palisade parenchyma thickness for all accessions. Chlorophyll levels did not differ according to the two light environments. The leaf area was larger in the protected environment. The essential oil yield of the accessions ranged from 0.26 to 0.87 mL/plant in full sun and from 0.34 to 0.53 mL/plant in the protected environment. The composition of the essential oil was influenced by the light and the accession. All accessions presented (E)-caryophyllene and α-humulene. The influence of light on the evaluated variables is genotype dependent.