Reduced Leaf Temperature Research Articles

Optimizing light intensity and airflow for improved lettuce growth and reduced tip burn disease in a plant factory

In practical plant factory production, light intensity and airflow were major environmental factors that significantly impacted lettuce growth and tip burn disease. This study investigated the effects of light intensity (100, 200, and 300 μmol·m-2·s-1) and airflow rate (100, 200, and 300 m³/h) on the comprehensive quality of lettuce. The Analytic Hierarchy Process (AHP) was employed to determine the weight of various growth and physiological indices of lettuce, while fuzzy mathematics principles were used to evaluate its comprehensive indices. The findings revealed that higher light intensity increased Ca2+ demand and decreased stomatal conductance, exacerbating tip burn disease. In contrast, increasing the airflow rate reduced leaf temperature, promoted transpiration, and facilitated calcium ion transport, thereby alleviating the occurrence of tip burn. Increasing the airflow rate to 300 m³/h effectively improved plant transpiration and Ca²⁺ transport, which further reduced tip burn. The comprehensive results indicated that under the conditions of a light intensity of 200 μmol·m-2·s-1 and an airflow rate of 300 m³/h, lettuce achieved the best comprehensive quality score of 0.6490, with a Ca2+ content of 21.83 mg/100 g, and tip burn was effectively suppressed. The study provided valuable scientific support for the precise control of environmental conditions in plant factories.

Ecotypic Variation in Leaf Thermoregulation and Heat Tolerance but Not Thermal Safety Margins in Tropical Trees.

To avoid reaching lethal temperatures during periods of heat stress, plants may acclimate either their biochemical thermal tolerance or leaf morphological and physiological characteristics to reduce leaf temperature (Tleaf). While plants from warmer environments may have a greater capacity to regulate Tleaf, the extent of intraspecific variation and contribution of provenance is relatively unexplored. We tested whether upland and lowland provenances of four tropical tree species grown in a common garden differed in their thermal safety margins by measuring leaf thermal traits, midday leaf-to-air temperature differences (∆Tleaf) and critical leaf temperatures defined by chlorophyll fluorescence (Tcrit). Provenance variation was species- and trait-specific. Higher ∆Tleaf and Tcrit were observed in the lowland provenance for Terminalia microcarpa, and in the upland provenance for Castanospermum australe, with no provenance effects in the other two species. Within-species covariation of Tcrit and ∆Tleaf led to a convergence of thermal safety margins across provenances. While future studies should expand the number of provenances and species investigated, our findings suggest that lowland and upland provenances may not differ substantially in their vulnerability to heat stress, as determined by thermal safety margins, despite differences in operating temperatures and Tcrit.

Harmonizing Growth Symphony: Unraveling the Intricacies of Apricot Seedling Enhancement Through Humic Acid and Silicon Applications

Understanding the physiological responses of apricot (Prunus armenica L.) seedlings to treatments involving Humic Acid (HA), Silicon (Si), and their combination (HA + Si) is crucial for advancing sustainable agricultural practices. Focused on growth parameters, physiological attributes, and leaf mineral concentrations, this study addressed critical knowledge gaps in the influence of these treatments on apricot seedlings. The study highlighted a significant increase in stomatal conductance (SC), with the combined HA + Si treatment displaying the highest SC value at 303.98 mmol.m-2s-1. In contrast, control seedlings of the Alyanak apricot cultivar showed the lowest SC, registering at 122.52 mmol.m-2s-1. Regarding chlorophyll concentrations, the Şekerpare apricot cultivar treated with HA + Si achieved the highest value of 43.74, while in the Alyanak apricot cultivar, the Si treatment alone marked the second highest concentration at 43.02. The combined treatment (HA + Si) also reduced leaf temperatures (32.28 °C), notably in apricot cultivar Hacıhaliloğlu. Visual evaluation analyses underscored significant increases in Leaf Area (LA), Total Leaf Number (TLN), Shoot Length (SL), and other parameters, with the combined HA + Si treatment consistently outperforming individual ones. Mineral analysis revealed elevated Nitrogen (N) and Phosphorus (P) with HA, increased Magnesium (Mg) with Si and HA + Si, and significant effects on Potassium (K) and Calcium (Ca). Principal Component Analysis (PCA) confirmed the positive impacts on overall plant performance, corresponding to a cumulative explanation of 53.82%. This study provided crucial insights for tailoring agricultural practices to optimize apricot seedlings growth, emphasizing the effectiveness of HA and Si treatments, particularly in combination, for enhanced physiological responses.

The contrasting photosynthesis and growth response of young test species irrigated with electro-chemical modified water

The study evaluated the effects of treating irrigation water with a coaxial flow variator (CFV) on the morpho-physiology of pot-cultivated test species, including cucumber (Cucumis sativus, CU), lettuce (Lactuca sativa, LE), and sorghum (Sorghum vulgare, SO), in early stages of growth. CFV caused a lower oxidation reduction potential (ORP), increased pH and flow resistance and inductance. It induced changes in the absorbance characteristics of water in specific spectral regions, likely associated with greater stretching and reduced bending vibrations compared to untreated water. While assimilation rate and photosynthetic efficiency were not significantly affected at 60 days after sowing, treated water increased the stomatal conductance to water vapour gsw (+79%) and the electron transport rate ETR (+10%) in CU, as well as the non-photochemical quenching NPQ (+33%) in SO. Treated water also reduced leaf temperature in all species (−0.86 °C on average). This translated into improved plant biomass (leaves: +34%; roots: +140%) and reduced leaf-to-root biomass ratio (−42%) in SO, allowing both faster aerial growth and soil colonization, which can be exploited to improve plant tolerance against abiotic stresses. In the C3 species CU and LE, plant biomass was instead reduced, although significantly in LE only, while the leaf-to-root biomass ratio was generally enhanced, a result likely profitable in the cultivation of leafy vegetables. This is a preliminary trial on the effects of functionalized water and much remains to be investigated in other physiological processes, plant species, and growth stages for the full exploitation of this water treatment in agronomy.

Effects of Light Intensity and Water Stress on Growth, Photosynthetic Characteristics and Plant Survival of Cistus heterophyllus Desf. Subsp. carthaginensis (Pau) M. B. Crespo & Mateo

The objective of this study was to identify the physiological mechanisms used by Cistus heterophyllus Desf. Subsp. carthaginensis (Pau) M. B. Crespo & Mateo, a species in critical danger of extinction, to cope with two typical abiotic conditions. During the summer of 2021, plants were cultivated under a shade mesh that intercepted 50% of the incident solar radiation (SHADE) and in natural conditions (SUN). Three irrigation treatments were also applied: control, T1, moderate water deficit; T2, 60% of the control, severe deficit; and T3, 30% of the control. Therefore, there were six treatments (SUN-T1, SUN-T2, SUN-T3, SHADE-T1, SHADE-T2, SHADE-T3). Plants were more affected by solar radiation than by deficit irrigation. Although leaf water potential, stomatal conductance and root biomass decreased by up to 45%, 63% and 65%, respectively, as deficit irrigation increased, plants were able to develop a leaf osmotic adjustment and an improved intrinsic water-use efficiency to maintain their growth and survival rate. Shade conditions improved gas exchange, reduced leaf temperature and induced the synthesis of chlorophylls, regardless of the irrigation level imposed. This indicated that radiation was the most limiting factor in our experiment. Applying 50% of the radiation and a moderate water deficit would help to obtain a good plant development and high survival rate in future recovery and conservation programs for the species.

The Mechanism by Which Umbrella-Shaped Ratchet Trichomes on the Elaeagnus angustifolia Leaf Surface Collect Water and Reflect Light.

Leaves are essential for plants, enabling photosynthesis and transpiration. In arid regions, water availability limits plant growth. Some plants, like Elaeagnus angustifolia, a sandy sub-tree species widely distributed in arid and semi-arid regions, have unique leaf structures to reduce water loss and solar radiation. Here, we describe the leaves of Elaeagnus angustifolia L., with special functioning trichomes. Through leaf submicroscopic structure observation, in situ water collection experiments, photosynthesis measurements, and reflection spectrum analysis, we investigated E. angustifolia leaves, focusing on their functioning trichomes. These trichomes capture water vapor, reflect UV and NIR light, and possess a 3D interface structure composed of 1D and 2D structures. The 1D conical structure captures water droplets, which are then gathered by the radial conical structure and guided towards the stomata through wedge-shaped grooves on the 2D umbrella structure. The trichomes also reflect sunlight, with micropapillae reflecting UV light and the umbrella structure reflecting NIR light. These mechanisms reduce leaf temperature, respiration, and water transpiration, protecting against solar radiation damage. This study provides insights into water collection and light-reflection mechanisms, revealing adaptive strategies of plants with large leaves in arid regions.

Estratégias de irrigação com água salina e adubação nitrogenada na cultura do milheto

ABSTRACT It is believed that nitrogen fertilization will attenuate the salt stress on pearl millet plants. Thus, the objective was to evaluate the agronomic performance of the millet crop under different saline water irrigation strategies and nitrogen fertilization. The experimental design adopted was completely randomized (CRD), in a 4 x 2 factorial scheme, with 4 replicates, with the first factor being four irrigation strategies: S1 = low-salinity water (W1) = 0.3 dS m-1 throughout the cycle; S2 = saline water (W2) = 4.0 dS m-1 from 30 days after sowing - DAS; S3 = W2 from 45 DAS; and S4 = W2 from 65 DAS; and the second factor being two nitrogen doses (60 and 120 kg ha-1 of N). At the end of the experiment, the following variables were evaluated: photosynthesis, transpiration, stomatal conductance, instantaneous water use efficiency, internal CO2 concentration, leaf temperature, plant height, stem diameter, root length, panicle length, leaf dry mass, stem dry mass and root dry mass. Fertilization with 60 and 120 kg ha-1 promotes greater photosynthesis, transpiration, stomatal conductance and internal CO2 concentration in millet plants under the strategies S1, S2 and S3. The strategies S1 and S4 were more efficient to increase the efficient use of water and reduce leaf temperature.

Photoselective particle films influence physiology and growth of citrus

Particle films impact pest management and crop physiology by redistributing light within the canopy. Although most commercial particle film products have nonselective reflectance, recent studies found positive effects of a red-dyed particle film on pest suppression and growth in citrus. To better understand the impacts of photoselective particle films on tree physiology and growth, we implemented a series of trials in citrus. Photoselective particle films of white (undyed), red, blue, purple, and green color were developed using photostable dyes. The experiment was repeated three times. In Trials 1 and 2 treatment rates were the same quantity of kaolin per treatment. However, because different photoselective films provided differences in shading, in Trial 3 the kaolin rates were adjusted to result in the same incident radiation to the leaves. We measured gas exchange and leaf temperatures midmorning and midday on multiple dates. All particle film treatments reduced leaf temperature (∼ 4–8 °C). Depending on environmental conditions, some particle films increased net CO2 assimilation or stomatal conductance especially white and red. Trees growing under red and white films resulted in higher total dry weights compared to the other colored films, and red films had the highest mean in all three trials. Photoselective particle films impacted both quantity and quality of incident radiation. The red-dyed kaolin film resulted in the best growth and physiological responses in citrus. These products represent an easily deployable technology to manipulate the light environment of crops in the field.

Reduction of heat stress pressure and activation of photosystem II repairing system are crucial for citrus tolerance to multiple abiotic stress combination.

Drought, heat and high irradiance are abiotic stresses that negatively affect plant development and reduce crop productivity. The confluence of these three factors is common in nature, causing extreme situations for plants that compromise their viability. Drought and heat stresses increase the saturation of the photosystem reaction centers, increasing sensitivity to high irradiance. In addition, these stress conditions affect photosystem II (PSII) integrity, alter redox balance of the electron transport chain and decrease the photosynthetic rate. Here, we studied the effect of the stress combinations on the photosynthetic apparatus of two citrus genotypes, Carrizo citrange (Citrus sinensis × Poncirus trifoliata) and Cleopatra mandarin (Citrus reshni). Results obtained showed that physiological responses, such as modulation of stomatal aperture and transpiration rate, aimed to reduce leaf temperature, are key to diminishing heat impact on photosynthetic apparatus and increasing tolerance to double and triple combinations of drought, high irradiance and high temperatures. By using transcriptomic and proteomic analyses, we have demonstrated that under these abiotic stress combinations, Carrizo plants were able to increase expression of genes and proteins related to the photosystem repairing machinery (which better maintained the integrity of PSII) and other components of the photosynthetic apparatus. Our findings reveal crucial physiological and genetic responses in citrus to increase tolerance to the combination of multiple abiotic stresses that could be the basis for breeding programs that ensure a sustainable citrus production.

Strategies to Reduce Radiation Stress in Open-Field Ginger and Turmeric Production

Excess solar radiation can negatively affect growth and rhizome yield of ginger (Zingiber officinale) and turmeric (Curcuma longa) plants. Thus, the objective of this study was to evaluate the effect of 60% shade nets (Experiment 1) as well as white and red kaolin sprays during two production stages (early establishment vs. entire cycle) (Experiment 2) on field-grown ginger and turmeric plants. In Experiment 1, plants were propagated from seed rhizomes (R) or second-generation rhizomes from tissue-cultured plants (2GR), while only R were used in Experiment 2. There were no differences in rhizome yield in response to shade in Experiment 1, with mean values of 644 and 692 g in ginger and turmeric, respectively. Overall, 2GR ginger plants produced a higher rhizome yield (880 g) than R plants (425 g), but no yield differences were measured in turmeric. In Experiment 2, for both species and regardless of kaolin color, sprays applied during the entire cycle increased photosynthesis and stomatal conductance and reduced leaf temperature and transpiration compared to control. Rhizome yield was also up to 87% higher in ginger and 47% higher in turmeric plants sprayed with kaolin. Spraying plants with white kaolin during the early season establishment of these crops can be an effective strategy to reduce radiation stress for open-field production.

Canopy-cooling systems applied on avocado trees to mitigate heatwaves damages

With climate change, spring heatwaves have become frequent in the Mediterranean region. High temperatures combined with wind and low humidity are problematic for subtropical crops adapted to high humidity and mild climate. Avocado is a valuable crop—nutritionally and economically—and many new orchards are planted in Mediterranean areas. Spring heatwaves increase avocado fruitlets dropping, severely decreasing yields. Addressing and solving the problem are necessary to maintain the crop's profitability. This study presents a sprinkler-based canopy cooling method that uses the existing pressurized irrigation system. The study aimed to test the system's performance during spring heatwaves, after the flowering season, in avocado orchards cultivated in a semi-arid region. The experiments examined the effect of various sprinkler types with varying flow rates and installation methods: sprayers, sprinklers and pulsing sprinklers, on foliage temperature, stem water potential, salt accumulation in the leaf, fruitlet survival and yield. The system reduced leaf temperatures by approximately 10 °C, significantly decreasing the trees' drought stress and increasing yields by 8–12%. Using low-quality water is possible, but requires adjustments to avoid salt damage to the leaves. The system can mitigate heat stress, and provides a relatively simple solution for handling spring heatwaves. The evaporative cooling system is modeled for semi-desert and desert conditions; the dry, windy climate contributes to the method's effectiveness.

Low-Phytate Grains to Enhance Phosphorus Sustainability in Agriculture: Chasing Drought Stress in lpa1-1 Mutant

Phytic acid (PA) is an anti-nutritional factor for monogastrics and contributes to phosphorus pollution. The low phytic acid (lpa) trait can provide several benefits to the nutritional quality of foods/feeds and to environmental sustainability. In maize, four lpa1 mutants have been isolated, and lpa1-1 is the most promising. Nevertheless, these mutations are frequently accompanied by many negative pleiotropic effects affecting plant performance. One of these is a greater susceptibility to drought stress, probably caused by an alteration in the root system. In this work, we set up an experiment in hydroponics and two in mesocosms, where pots were built using transparent PVC sheets to better access the roots. The results suggested that neither root architecture nor root depth are limiting factors in mutant plants. In hydroponics, the dry weight of the mutant and the root area per unit of length were twice that of B73. However, lpa1-1 exhibited a reduced efficiency of photosystem II (Fv/Fm, 0.810 vs. 0.800) and a reduced leaf temperature (−0.5 °C compared to wild-type), probably due to increased water loss. Furthermore, molecular analysis performed on genes involved in root development (rtcs, rtcl, rum1, and BIGE1) revealed the abundance of rtcs transcripts in the mutant, suggesting an alteration in auxin polar transport.

Innovation in grapevine water status monitoring and drought adaptation: leaf angle and temperature regulation

Increase of frequency, duration, and intensity of drought and heatwave and related water and heat crops stress are among the principal effects of climate change. This paper reports: (i) the effect of calcite particle film (CaPF) as a mitigation strategy against heat stress in well-watered (WW) or in drought-stress (D) conditions; and (ii) response of leaf angle variation to stomatal conductance changes induced by drought stress of Aleatico grapevine cultivar. Results have showed that CaPF, under WW conditions, reduced leaf temperature, and increased gas exchange, but, under very severe water stress, CaPF treatment was ineffective. Leaf angle ranged from 70° (WW vines) to 100° (drought stressed vines) and showed a good fit (R2=0.81) with stomatal conductance within the range of 0.25 – 0.05 mol m-2s–1proving it might be a reliable proxy of vine water status.

Relação entre fisiologia e produção de milho sob diferentes reposições hídricas no semiárido brasileiro

ABSTRACT Water restriction causes physiological disorders and reduces maize yield in semi-arid regions. The objective of this study was to correlate instantaneous physiological variables with the grain yield of maize using different replacement percentages of water lost through evapotranspiration and to fit a multiple regression model to estimate grain yield in the dry season in the Brazilian semi-arid region. The experiment was installed in a randomized block design, with six percentages of reference evapotranspiration (ETo) repositioning (50, 75, 100, 125, 150, and 175%). The AG 7088 hybrid had a higher CO2 assimilation rate, stomatal conductance, transpiration, and instantaneous water use efficiency, and reduced leaf temperature and vapor pressure deficit under full irrigation (100% of ETo, 458 mm), with yields of 5.75 t ha-1, reaching 6.8 t ha-1 (572 mm) and 7.65 t ha-1 (801 mm) with replacements of 125 and 175% of ETo, respectively. Measurements of leaf gas exchange, vapor pressure deficit, and leaf temperature can be performed at phenological stage R1 to estimate grain yield with greater robustness when combined with water rates applied during the crop cycle.

Effects of Siliceous Natural Nanomaterials Applied in Combination with Foliar Fertilizers on Physiology, Yield and Fruit Quality of the Apricot and Peach Trees.

Siliceous natural nanomaterials (SNNMs), i.e., diatomaceous earth and natural zeolites, have a nanoporous structure with large active surfaces that adsorb cations or polarized molecules. Such nanoporous feature determines the effects related to SNNM utilization as low-risk plant protectants and soil improvers. This work used SNNMs from Romanian quarries as carriers for foliar fertilizers applied to stone-fruit trees, apricot and peach. We determined the effects of SNNMs on the physiology, yield and fruit quality of the treated stone-fruit trees. SNNM application determined impacts specific to the formation of particle films on leaves: reduced leaf temperature (up to 4.5 °C) and enhanced water use efficiency (up to 30%). Foliar fertilizers’ effects on yield are amplified by their application with SNNMs. Yield is increased up to 8.1% by the utilization of SNNMs with foliar fertilizers, compared to applying foliar fertilizer alone. Diatomaceous earth and natural zeolites promote the accumulation of polyphenols in apricot and peach fruits. The combined application of SNNMs and foliar fertilizer enhance the performance of peach and apricot trees.

Effects of natural clinoptilolite on physiology, water stress, sugar, and anthocyanin content in Sanforte (Vitis viniferaL.) young vineyard

AbstractIn the Mediterranea area, major effects of climate change are a modification in rainfall patterns, an increase in temperature with an intensify in tropical nights, and an increase in incoming radiations, especially UV-Bs. Despite the various adaptation strategies, grapevines are sensitive to altered climatic conditions. This paper aims to assess the benefits of applying a new sustainable product to the soil that can implement farmers’ resources to adapt to this changing situation. Zeowine was realized by combining the properties of zeolite, which has excellent potential in many sectors such as in agriculture, with the organic substance of a compost obtained on a company scale from the reuse of waste processing grapes, pomace and stalks. The effects of two different soil management (Z – Zeowine, 30 t/ha dose and C – Compost, 20 t/ha dose) on vine physiology and berry compositions in Sanforte grapevines (new plantation) were studied during the 2019–2020–2021 growing seasons in the San Miniato area, Italy. The following physiological parameters of grapevines were measured: leaf gas exchange, leaf temperature, stem water potential and chlorophyll fluorescence. The results showed that Z increased single leaf photosynthesis, reduced leaf temperature and water stress. In addition, phenolic and technological parameters were studied. The Z-treated vines had higher sugar content and total and extractable anthocyanin content as well as berry weight. These results suggested that the application of zeolites added to compost in the vineyard to the soil can be a valid tool to mitigate the effects of climate change.

Phytochemical screening and antioxidant activity on berry, skin, pulp and seed from seven red Mediterranean grapevine varieties (Vitis vinifera L.) treated with kaolin foliar sunscreen

In the latest decades, global warming impacts become an emergent issue, and short-term techniques such as kaolin have been proposed to mitigate summer stress effects on Mediterranean viticulture. Nevertheless, the impact of this technology on grape berry composition, particularly on different fractions of whole berry (skin, pulp, and seed) is not yet studied, being these data crucial to the expansion of waste and by-product industry.Thus, the purpose of the present study was to fulfill the identified gap of knowledge by investigating how a pre-veraison kaolin (5% w/v) exogenous application may impact secondary metabolites and antioxidant capacity (ABTS+ and DPPH methods) at veraison and maturation, in whole berries and their fractions (skin, pulp, and seed), from seven red varieties (‘Touriga Franca’, ‘Touriga Nacional’, ‘Tinta Francisca’, ‘Vinhão’, ‘Grenache’, ‘Borraçal’, and ‘Cornifesto’) under Mediterranean conditions conjugated with global warming. Afterwards, biometric, color and oenological parameters (soluble solids, pH, acidity, and soluble protein) were also quantified in whole berries. Our findings indicate that kaolin increased the berry size (up to 62.2 %) which reduced the skin-to-pulp weight ratio and consequently the anthocyanins contents (reaching − 41.7 %). Additionally, particle film reduced leaf temperature (until – 11.78 %) avoiding thermal stress which seems to decrease the production of proteins in grape berries treated (up to – 27.01 %), indicating a potential reduction of heat shock proteins production. Our results enlighten that it was crucial to analyze the several fractions of grape berries separately, because output resulting from the whole berry might lead to an inaccurate conclusion. In this vein, although often no changes were reported in the whole berry, when analyzing their specific fractions, we found that kaolin enhanced the production of secondary metabolites and antioxidant capacity in the seed (reaching 49,40 and 48.29 %, respectively), leading to a positive influence on berry quality which might be favorable to industrial by-products expansion. The findings also support that kaolin can represent a resilience strategy aiming to improve berry quality under the changing climatic scenario.

INFLUÊNCIA DA IRRIGAÇÃO SUPLEMENTAR COM ÁGUAS RESIDUÁRIAS SOBRE AS TROCAS GASOSAS FOLIARES DO ALGODOEIRO

INFLUÊNCIA DA IRRIGAÇÃO SUPLEMENTAR COM ÁGUAS RESIDUÁRIAS SOBRE AS TROCAS GASOSAS FOLIARES DO ALGODOEIRO
 
 ADRIANA CRUZ DE OLIVEIRA1; ANTONIO FLAVIO BATISTA DE ARAUJO2; CLAUDIVAN FEITOSA DE LACERDA3; JUVENALDO FLORENTINO CANJÁ4; LUCIANA LUZIA PINHO5 E NAARA IORRANA GOMES SOUSA6
 
 
 1 Mestranda no Programa de Pós-Graduação em Engenharia Agrícola, Departamento de Engenharia Agrícola, Universidade Federal do Ceará-UFC, Av. Mister Hull, s/n -Pici, Centro de Ciências Agrárias, Bloco 804, CEP: 60455-760, Fortaleza-CE, Brasil. E-mail: drica_fj@hotmail.com.br
 2 Doutorando no Programa de Pós-Graduação em Engenharia Agrícola, Departamento de Engenharia Agrícola, Universidade Federal do Ceará-UFC, Av. Mister Hull, s/n -Pici, Centro de Ciências Agrárias, Bloco 804, CEP: 60455-760, Fortaleza-CE, Brasil. E-mail: antonioflaviobatistadearaujo@gmail.com
 3 Professor Titular do Departamento de Engenharia Agrícola, Universidade Federal do Ceará-UFC, Av. Mister Hull, s/n -Pici, Centro de Ciências Agrárias, Bloco 804, CEP: 60455-760, Fortaleza-CE, Brasil. E-mail: cfeitosa@ufc.br
 4Mestrando no Programa de Pós-Graduação em Engenharia Agrícola, Departamento de Engenharia Agrícola, Universidade Federal do Ceará-UFC, Av. Mister Hull, s/n -Pici, Centro de Ciências Agrárias, Bloco 804, CEP: 60455-760, Fortaleza-CE, Brasil. E-mail: batchijuve@gmail.com
 5 Mestranda no Programa de Pós-Graduação em Engenharia Agrícola, Departamento de Engenharia Agrícola, Universidade Federal do Ceará-UFC, Av. Mister Hull, s/n -Pici, Centro de Ciências Agrárias, Bloco 804, CEP: 60455-760, Fortaleza-CE, Brasil. E-mail: englucianaufc@gmail.com
 6 Mestranda no Programa de Pós-Graduação em Engenharia Agrícola, Departamento de Engenharia Agrícola, Universidade Federal do Ceará-UFC, Av. Mister Hull, s/n -Pici, Centro de Ciências Agrárias, Bloco 804, CEP: 60455-760, Fortaleza-CE, Brasil. E-mail: naara_iorrana@hotmail.com
 
 
 1 RESUMO
 
 O uso de águas residuárias na irrigação tem crescido como suplementação para driblar a escassez hídrica. Contudo, pouco se sabe sobre as respostas das culturas sobre sua aplicação. Assim, objetivou-se avaliar os impactos da irrigação suplementar com águas residuárias tratadas sobre as trocas gasosas do algodoeiro (Gossypium hirsutum L), simulando-se cenários hídricos considerados normais, seca e seca severa, na presença e ausência de NPK. O experimento foi conduzido no município de Russas – CE, em área vizinha à lagoa de estabilização da CAGECE – Companhia de Água e Esgoto do Estado do Ceará, em DBC, no esquema de parcelas subsubdivididas, com quatro blocos. As parcelas foram cenários hídricos (normal, seca e seca severa); a subparcela foi a suplementação ou não com água residuária tratada nos veranicos simulados; a subsubparcela foi a aplicação ou não de NPK. A cultivar utilizada foi BR 433. Aos 25 dias após a semeadura foram analisadas fotossíntese, transpiração, concentração interna de CO2 e temperatura foliar. Os cenários de seca e seca severa apresentaram pequeno impacto sobre as trocas gasosas foliares do algodoeiro. Entretanto, a irrigação suplementar reduziu a temperatura foliar e atenuou os efeitos do cenário de seca sobre a fotossíntese, independente da aplicação ou não de NPK.
 
 Palavras-chave: Gossypium hirsutum L, Reúso de água, Seca.
 
 
 
 
 OLIVEIRA, A. C. de; ARAUJO, A. F. B. de; LACERDA, C. F. de; CANJÁ, J. F.; PINHO, L. L.; SOUSA, N. I. G.
 INFLUENCE OF SUPPLEMENTAL IRRIGATION WITH WASTEWATER ON COTTON LEAF GAS EXCHANGE
 
 
 2 ABSTRACT
 
 The use of wastewater in irrigation has grown as a supplement to circumvent water scarcity. However, little is known about the responses of cultures to its application. Thus, the objective was to evaluate the impacts of supplementary irrigation with treated wastewater on gas exchange of cotton (Gossypium hirsutum L), simulating water scenarios considered normal, drought and severe drought, in the presence and absence of NPK. The experiment was conducted in the municipality of Russas - CE, in an area next to the stabilization pond of CAGECE - Companhia de Agua e Esgoto do Estado do Ceará, in DBC, in the subdivided plot scheme, with four blocks. The plots were water scenarios (normal, drought and severe drought); the subplot was supplemented or not with wastewater treated in the simulated summer days; the sub-installment was the application or not of NPK. The cultivar used was BR 433. At 25 days after sowing, photosynthesis, transpiration, internal CO2 concentration and leaf temperature were analyzed. The drought and severe drought scenarios had little impact on the cotton leaf gas exchange. However, supplementary irrigation reduced leaf temperature and attenuated the effects of drought scenario on photosynthesis, whether or not NPK was applied.
 
 Keywords: Gossypium hirsutum L, Water reuse, Drought.

Effect of a mist culture system on photosynthesis and nitrogen metabolism in ginger.

To evaluate the transition from traditional shading cultivation to mist cultivation, a field experiment was carried out. The results demonstrated that compared with traditional shading, the mist treatment significantly reduced leaf temperature. Likewise, the higher transpiration rate also contributes to reducing leaf temperature and protects ginger from heat stress in summer. Moreover, a higher instantaneous efficiency of water use suggested that water lost via transpiration was beneficial under a mist culture system. The higher instantaneous efficiency of water use in the mist treatment was caused mainly by the higher net photosynthetic rate, which is further reflected by the higher rhizome yield of ginger under the mist culture system. Instead of lowering the temperature by lowering photon flux density, mist treatment does not seriously reduce the photon flux density while reducing the temperature of the blade. Hence, the net photosynthetic rate in the shading treatment is significantly lower than that in the mist treatment, although the maximal quantum yield of photosystem II and the actual photochemical efficiency of photosystem II in ginger in the shading treatment were significantly higher than those in the mist treatment. Lower superoxide anion, hydrogen peroxide, and malondialdehyde contents were also found after mist treatment. Lower ammonium avoids the potential risk of ammonium toxicity and is based on higher nitrate reductase, glutamine synthetase, and glutamate synthase activity but lower glutamate dehydrogenase activity. Therefore, the mist cultivation system improved the physiological characteristics and yields of ginger and can be suggested as an alternative, sustainable, and cleaner cultivation measure.

Identification of a transcriptional regulatory module that reduces leaf temperature in poplar under heat stress.

A stable leaf temperature provides plants with a suitable microenvironment for photosynthesis. With global warming, extreme temperatures have become more frequent and severe; therefore, it is increasingly important to understand the fine regulation of leaf temperature under heat stress. In this study, five poplar species (Populus tomentosa, Populus simonii, Populus euphratica, Populus deltoides and Populus trichocarpa) that live in different native environments were used to analyze leaf temperature regulation. Leaf temperatures were more stable in Populus simonii and Populus euphratica (adapted to water-deficient regions) under elevated ambient temperature. Although transpiration contributes strongly to leaf cooling in poplar, the thicker epidermis and mesophyll and lower absorbance of Populus simonii and Populus euphratica leaves also help reduce leaf temperature, since their leaves absorb less radiation. Co-expression network and association analysis of a natural population of P. simonii indicated that PsiMYB60.2, PsiMYB61.2 and PsiMYB61.1 play dominant roles in coordinating leaf temperature, stomatal conductance and transpiration rate in response to heat stress. Individuals with CT-GT-GT genotypes of these three candidate genes have significantly higher water-use efficiency, and balance leaf temperature cooling with photosynthetic efficiency. Therefore, our findings have clarified the genetic basis of leaf cooling among poplar species and laid the foundation for molecular breeding of thermostable, water-conserving poplar varieties.