ABSTRACT Light stress damages the photochemical apparatus and affects seedling growth of forest species. Using potassium silicate (K2SiO3) can mitigate these deleterious effects and contribute to the acclimatization and robustness of seedlings. This study evaluated the effect of K2SiO3 and shading levels on the photochemical and growth of Alibertia edulis (Rich) A. Rich seedlings. The experiment was arranged under three light conditions based on shading levels of 0 % (full sun), 30 %, and 70 %. Four doses of K2SiO3 applied through foliar spray were tested: 0.0, 2.5, 5.0, and 10.0 mL L–1. Cultivation under full sun and under 70 % of shade was stressful for A. edulis, while cultivation under 30 % of shade improved plant growth. Increasing application of K2SiO3 in seedlings under full sun damaged the reaction center, causing lower photochemical yields, but increased the photochemical efficiency of photosystem II under 30 % of shade. Using K2SiO3 contributed to leaf water regulation while applying 10.0 mL L–1 increased chlorophyll indices, leaf area, physiological indices, and the quality of seedlings cultivated under full sun and 30 % of shade. Using 10.0 mL L–1 K2SiO3 mitigated the negative effects of light stress under full sun. It provided high photochemical efficiency, morphology aspects, and Dickson quality index A. edulis seedlings in environments with high or moderate light availability. species KSiO K SiO (K2SiO3 K2SiO (Rich A sun, , sun) 3 7 tested 00 0.0 25 2 5 2.5 50 5.0 100 10 10. L1 L 1 center yields L– indices area aspects availability (K2SiO 0. 2. 5.

ABSTRACT Using organic residues and bioinputs is a promising and sustainable practice to produce seedlings with forest essences, such as Cedrela fissilis Vell. (cedar), a vulnerable species close to extinction due to intensive exploitation in native areas. Thus, we aimed to evaluate the effect of different substrates based on organic residues associated with or without the application of Parachlorella sp. microalgae in the emergence and morphophysiology of C. fissilis seedlings. Sowing was carried out on six substrates: Oxisol with a clayey texture; Oxisol + Parachlorella sp.; Oxisol with sheep manure (3:1, v v–1); Oxisol with sheep manure + Parachlorella sp.; Oxisol with cattle manure (3:1, v v–1); and Oxisol with cattle manure + Parachlorella sp. The addition of organic residues to the soil, especially cattle manure, contributes to increasing the percentage of emergence, plant height, chlorophyll index, CO2 assimilation rate, and instantaneous carboxylation efficiency of Rubisco due to the superior chemical attributes in the substrate, which promote greater physiological efficiency. Organic residues increased the water use efficiency of seedlings. The application of Parachlorella sp. microalgae contributes to increases in the CO2 assimilation rate and stomatal conductance when seedlings are grown only in Oxisol. C. fissilis seedlings produced in the substrate with sheep and cattle manure showed better growth and gas exchange characteristics. essences Vell cedar, cedar , (cedar) areas Thus sp C texture 31, 31 3 1, 1 (3:1 v–1 v1 v–1) soil height index CO characteristics (cedar (3: v– (3 (

Resumo Nesta pesquisa, hipotetizamos que as mudas de Ormosia arborea (Vell.) Harms crescem melhor e alcançam maiores níveis de troca gasosas quando cultivadas em solos com maior disponibilidade de água. Assim, este estudo foi desenvolvido para avaliar as respostas metabólicas das mudas a diferentes níveis de disponibilidade hídrica. A irrigação foi realizada em dias alternados, nas capacidades de retenção de água (CRA) de 25%, 50%, 75% e 100%. As respostas metabólicas foram analisadas aos 15, 50, 85 e 120 dias após o início dos tratamentos. As plantas de O. arborea cultivadas em condições de maior disponibilidade hídrica (75% e 100% CRA) apresentaram maior potencial hídrico foliar e teor de clorofila, além de maiores valores para a fluorescência da clorofila a e trocas gasosas do que aquelas cultivadas em outras condições. O déficit hídrico causado por baixos níveis de disponibilidade hídrica (25% ou 50% CRA) reduz o potencial hídrico foliar, a fluorescência da clorofila a e as trocas gasosas. Como estratégia para tolerar o estresse, as mudas tendem a investir em seu sistema antioxidante, como demonstrado pelos altos níveis de atividade das enzimas Superóxido dismutase (SOD), Peroxidase (POD) e Catalase (CAT). Embora as mudas possam ser tolerantes ao cultivo com menos de 50%, o melhor funcionamento do aparato fotossintético ocorreu sob 75% de CRA. pesquisa Vell. Vell (Vell. Assim alternados CRA (CRA 25 25% 50 75 100 15 8 12 tratamentos (75 (25 estresse antioxidante SOD, SOD , (SOD) POD (POD CAT. CAT . (CAT) (Vell 2 5 7 10 1 (7 (2 (SOD (CAT (

Abstract In this research, we hypothesized that Ormosia arborea (Vell.) Harms seedlings should grow better and achieve greater levels of gas exchange when grown in soils with higher water availability. Thus, this study was developed to assess the metabolic responses of the seedlings to different levels water availability. Irrigation was performed on alternate days, at water holding capacities (WHC) of 25%, 50%, 75%, and 100%. The metabolic responses were analyzed at 15, 50, 85, and 120 days after starting treatments. The O. arborea plants grown in conditions of higher water availability (75% and 100% WHC) had higher leaf water potential and chlorophyll content, in addition to higher values for chlorophyll a fluorescence and gas exchange, than those grown in other conditions. Water deficit caused by low levels of water availability (25% or 50% WHC) reduces leaf water potential, chlorophyll a fluorescence, and gas exchange. As a strategy to tolerate stress, seedlings tend to invest in their antioxidant system, as shown by the high levels of activity of the enzymes Superoxide dismutase (SOD), Peroxidase (POD), and Catalase (CAT). Although the seedlings may be tolerant to cultivation under 50% WHC, the best functioning of the photosynthetic apparatus occurred under WHC of 75%. research Vell. Vell (Vell. Thus (WHC 25 25% 50 75 75% 100 15 85 12 treatments O (75 content (25 stress system SOD, SOD , (SOD) POD, POD (POD) CAT. CAT . (CAT) (Vell 2 5 7 10 1 8 (7 (2 (SOD (POD (CAT (

Resumo Myrciaria glomerata O. Berg. (Myrtaceae) é uma frutífera nativa da Mata Atlântica com potencial alimentício, medicinal e ecológico, mas com baixa taxa de germinação. Objetivou-se com este trabalho avaliar diferentes métodos na superação da dormência de sementes e no vigor de plântulas de M. glomerata. Foram realizados dois experimentos. No experimento 1, foram testados sete tratamentos: controle; imersão em água a 100 ºC por 30 segundos; imersão em ácido sulfúrico concentrado (H2SO4) por 1 e 5 minutos; imersão em solução aquosa de ácido giberélico (AG3) 250 e 500 mg L-1 e imersão em solução aquosa com 5 mL de Stimulate® kg-1 de sementes. No experimento 2, foram testadas sete doses de Stimulate®: 0; 5; 10; 15; 20; 25 e 30 mL kg-1 de sementes. A imersão das sementes em 250 e 500 mg L-1 AG3 contribui na velocidade de germinação e maior comprimento, massas frescas e secas, em comparação às do controle e aos outros métodos testados. A imersão em água a 100 ºC e em H2SO4 não é recomendada para M. glomerata. As doses de 20 a 25 mL de Stimulate® kg-1 de sementes proporcionam incremento para todas as características anali-sadas. Imersão em AG3, na concentração de 250 mg L-1, e doses de 15 a 25 mL de Stimulate® kg-1 de sementes são eficientes para a superação da dormência de sementes e o vigor de plântulas de M. glomerata.

Abstract Myrciaria glomerata O. Berg. (Myrtaceae) is a fruit tree native to the Brazilian Atlantic Forest with potential for use as food and medicine, besides having good ecological potential. However, this species is limited by low germination rates. Thus, this study aimed to evaluate different methods to overcome dormancy in seeds of M. glomerata and to improve seedling vigor. For this, two experiments were conducted. In Experiment 1, seven treatments were tested: a control treatment, immersion in water at 100 ºC for 30 seconds, immersion in concentrated sulfuric acid (H2SO4) for 1 and 5 minutes, immersion in an aqueous solution of gibberellic acid (GA3) at the concentrations of 250 and 500 mg L-1 for 24 h, and seeds homogenized with an aqueous solution of Stimulate® at a concentration of 5 mL kg-1 seed. In Experiment 2, six doses of Stimulate® were tested: 0, 5, 10, 15, 20, 25, and 30 mL kg-1 seed. The immersion of seeds in 250 and 500 mg L-1 GA3 contributes to increase germination rates, seed length, fresh mass, and dry mass compared to the control and the other methods tested. Immersions in water at 100 ºC and in H2SO4 are not recommended for M. glomerata. The treatment with Stimulate® at 15–25 mL kg-1 seed increased all characteristics analyzed. Immersion in 250 mg L-1 GA3 and Stimu-late® at 20–25 mL kg-1 seed efficiently stimulated seeds to overcome dormancy in M. glomerata, as well as improved seedling vigor.

Resumo O objetivo deste estudo foi avaliar o potencial do sombreamento na redução do efeito estressante do déficit hídrico sobre o metabolismo fotossintético e antioxidante, favorecendo o crescimento de mudas de Ormosia arborea e sua recuperação metabólica. Os níveis de sombreamento estudados foram: 0, 30 e 70%. Foram implantados dois regimes hídricos: controle, em que as plantas foram irrigadas a 75% da capacidade de retenção de água no solo e restrição hídrica, em que a irrigação foi suspensa até que a taxa fotossintética atingisse valores próximos a zero (F0), período em que as mudas foram re-irrigadas. Ocorreram dois períodos de avaliação: F0 e recuperação. Observamos que a restrição hídrica reduz o metabolismo fotossintético, o crescimento e a qualidade das mudas de O. arborea, aumentando a atividade de enzimas antioxidantes. As mudas apresentam maior índice de qualidade, condutância estomática, eficiência de carboxilação da Rubisco e transpiração quando cultivadas sob sombreamento de 70% na recuperação. O efeito estressante da restrição hídrica foi mitigado pelo sombreamento de 70% quando as mudas foram capazes de se recuperara, retomando seu metabolismo fotossintético e qualidade após a retomada da irrigação. Além disso, 0% de sombreamento não é indicado para essa espécie.

Abstract This study aimed to evaluate the potential of shading in reducing the stressful effect of water restriction on photosynthetic and antioxidant metabolism, favoring the growth of Ormosia arborea seedlings and the recovery metabolic. The shadings levels studied were: 0, 30 and 70%. Two water regimes were implemented: control, in which the plants were irrigated at 75% of soil water retention capacity and water restriction, in which the irrigation was suspended until the photosynthetic rate reached values close to zero (P0), period at which the seedlings were re-irrigated. There were two evaluation periods: P0 and recovery. We observed that water restriction reduced photosynthetic metabolism, growth and quality of O. arborea seedlings by increasing the activity of antioxidant enzymes. The seedlings present higher quality index, stomatal conductance, intrinsic carboxylation efficiency and transpiration when cultivated under 70% shading in recovery. The stressful effect of water restriction was mitigated by the shading of 70%, where the seedlings were able to recover, resuming their photosynthetic metabolism and quality after resumption of irrigation. In addition, 0% shading is not indicated for this species.

Resumo O alagamento do solo restringe a disponibilidade do oxigênio necessário para ativação dos processos fisiológicos do embrião e que caracterizam a germinação de sementes. No entanto, algumas espécies apresentam adaptações que permitem seu crescimento natural em áreas sujeitas a inundações, como Ormosia arbórea, espécie nativa da Mata Atlântica e do Cerrado. O objetivo deste trabalho foi avaliar como a germinação e emergência das sementes desta espécie foram afetadas pela submersão em água e escarificação. No experimento 1, as sementes foram escarificadas por 15 minutos em ácido sulfúrico e posteriormente semeadas em tubetes submersos em água por 0, 15, 30 e 45 dias. Nos experimentos 2 e 3, as sementes foram submersas em água corrente pelo mesmo período e, após cada tempo de submersão, foram escarificadas por 0, 5, 10 e 15 minutos em ácido sulfúrico e semeadas em tubetes e em papel Germitest®. Verificou-se que, após a quebra da dormência tegumentar, 15 dias de alagamento são suficientes para inviabilizar a germinação das sementes de O. arborea que toleram a submersão em água quando estão intactas. Este resultado indica que o tegumento rígido e impermeável da semente é uma importante característica da semente para essa resposta.

Abstract Soil flooding restricts the availability of the oxygen necessary to activate the embryonic physiological processes that characterize seed germination. However, some species have adaptations that allow them to grow naturally in areas prone to flooding, such as Ormosia arborea, a native species of the Atlantic forest and the Cerrado. The objective of this work was to evaluate how seed germination and emergence in this species were affected by submersion in water and scarification. In experiment 1, the seeds were scarified by 15 minutes in sulfuric acid and was subsequently sown in tubes submerged in water for 0, 15, 30 and 45 days. In experiments 2 and 3, seeds were submerged in running water for the same period and, after each time of submersion, were scarified by 0, 5, 10 and 15 minutes in sulfuric acid and sown either in tubes and in Germitest® paper. It was found that, after breaking the tegumental dormancy, 15 days of flooding is enough to derail the germination of O. arborea seeds that tolerate submersion in water when they are intact. This response indicates that the hard, impermeable seed coat is an important seed characteristic for this response.

Resumo Este trabalho teve como objetivo avaliar o efeito da aplicação exógena de ácido salicílico sobre o metabolismo fotossintético e a qualidade de mudas de Eugenia myrcianthes sob deficiência hídrica e seu potencial de recuperação após reidratação. Foram avaliados dois regimes hídricos: controle - plantas irrigadas diariamente (I) e déficit hídrico (S), com e sem a aplicação de 400 mg L–1 de ácido salicílico (AS), totalizando quatro tratamentos. As mudas foram avaliadas em três momentos: no início do experimento (T0) quando a irrigação foi interrompida; quando a taxa fotossintética atingiu valores próximos a zero (F0 - 15 dias após a suspensão hídrica), quando a irrigação foi reiniciada; e quando a taxa fotossintética foi recuperada (REC). Mudas de E. myrcianthes foram afetadas negativamente quando submetidas à restrição hídrica; o ácido salicílico atenuou os danos ao aparato fotossintético por agir positivamente sobre o conteúdo relativo de água nas folhas, índice SPAD, metabolismo fotossintético, atividade das enzimas superóxido dismutase e peroxidase e crescimento das mudas na F0. Eugenia myrchiantes apresentou potencial de recuperação após a retomada da irrigação. A aplicação de AS contribuiu na manutenção das trocas gasosas, processos fotoquímicas e qualidade de mudas de E. myrcianthes durante e após o deficit hídrico, sugerindo a promoção da indução de resistência de plantas.

Abstract This study aimed to evaluate the effect of exogenous application of salicylic acid on the photosynthetic metabolism and quality of Eugenia myrcianthes seedlings under water deficit and their recovery potential after rehydration. Two water regimes were evaluated, as follows: control - plants irrigated daily (I) and water deficit (S), with and without the application of 400 mg L–1 of salicylic acid (SA), totaling four treatments. Seedlings were evaluated at three times: at the beginning of the experiment (T0), that is, when the irrigation was interrupted; when the photosynthetic rate reached values close to zero (P0 - 15 days after irrigation interruption), that is, when irrigation restarted; and when the photosynthetic rate was recovered (REC). Eugenia myrcianthes seedlings were negatively affected when subjected to water restriction; salicylic acid attenuated the damage to the photosynthetic apparatus by acting positively on the relative water content in the leaves, SPAD index, photosynthetic metabolism, superoxide dismutase and peroxidase enzyme activity, and seedling growth in P0. Eugenia myrchiantes presented potential for recovery after resumption irrigation. The application of SA contributed to the maintenance of gas exchanges, photochemical processes and quality of E. myrcianthes seedlings during and after water deficit, suggesting the promotion of plant resistance induction.

ABSTRACT The objective of this work is to evaluate the use of modified atmosphere and chitosan as an alternative to chemical treatment in postharvest conservation of ‘Tainung 1’ papaya under refrigeration. The experiment comprised of completely randomized blocks with four replications, one fruit per replication, with a 2 × 4 × 4 factorial design as follows: two types of packaging (with or without polyvinyl chloride [PVC] stretchable film, thickness of 17 µm), four treatments (control, 2% chitosan, 4% chitosan, and prochloraz fungicide with 33.75 g a.i.·100 L–1), and four storage periods (0, 7, 14, and 21 days) at 10 °C and relative humidity (RH) of 90 ± 5%. The variables evaluated were mass loss (ML), external appearance, titratable acidity (TA), soluble solids (SS), vitamin C, reducing sugars (RS), and total sugars (TS). The storage of ‘Formosa’ papaya under refrigeration at 10 °C and RH of 90 ± 5% associated with PVC provided a low percentage of ML and longer conservation time of apparent quality (up to 7 days) in relation to fruits with no storage in PVC. The external appearance of fruits was preserved for up to 14 days by the PVC + 4% chitosan treatment and for up to 21 days by the PVC + prochloraz fungicide treatment. The treatment PVC + 4% chitosan associated with refrigeration is efficient in maintaining fruit quality. It is, for up to 14 days, a viable alternative to the use of prochloraz fungicide for postharvest conservation of ‘Formosa’ papaya.

Resumen El objetivo de este estudio fue evaluar el efecto del aluminio y el potencial mitigante del H2O2 sobre el estrés y las respuestas antioxidantes en la canola (Brassica napus var. oleifera (Moench) Delile) que afectan la emergencia y el crecimiento inicial de las plantas. Semillas de canola, cultivar Hyola 61, fueron tratadas con diferentes concentraciones de solución H2O2 (0.0, 0.075 y 0.15 M) y posteriormente sembradas bajo diferentes concentraciones de aluminio (0.0, 10, 20 y 30 mmolc dm-3). Después de 20 días de emergencia de la planta, se evaluaron las características de supervivencia y crecimiento. 20, 30, 40, 50 y 60 días después de la emergencia en altura, se determinó el índice de clorofila, la fluorescencia de la clorofila a y la actividad del superóxido dismutasa en las raíces. La canola fue sensible al aluminio y el tratamiento de semillas con H2O2 0.15 M mitigó el estrés causado por la dosis más alta de aluminio. El tratamiento con H2O2 permitió una alta emergencia, pero no favoreció la supervivencia ni el crecimiento de las plántulas. El H2O2 no aumentó la actividad de la SOD. Las variables de fluorescencia de la clorofila a demostraron la sensibilidad de la canola al aluminio, pero la presencia de H2O2 mantuvo la estabilidad y funcionalidad del fotosistema II.

Abstract The objective of this study was to evalúate the effect of aluminum and the mitigating potential of H2O2 on the stress and antioxidant responses in canola (Brassica napus var. oleifera (Moench) Delile) affecting the emergence and initial growth of plants. Canola seeds, cultivar Hyola 61, were treated with different concentrations of H2O2 solution (0.0, 0.075, and 0.15 M), and later sown under different concentrations of aluminum (0.0, 10, 20, and 30 mmolc dm-3). After 20 days of plant emergence, survival and growth characteristics were evaluated. 20, 30, 40, 50, and 60 days after emergence, height, chlorophyll index, chlorophyll a fluorescence, and the activity of superoxide dismutase in the roots were determined. The canola is sensitive to aluminum, and the treatment of seeds with H2O2 0.15 M mitigated the stress caused by the highest dose of aluminum. H2O2 treatment enabled high emergence but did not favor seedling survival or growth. The H2O2 did not increase SOD activity. The chlorophyll a fluorescence characteristics proved the sensitivity of canola to aluminum, but the presence of H2O2 maintained the stability and functionality of photosystem II.

Abstract The aim this study was to evaluate the effect of salicylic acid (SA) in Schinus terebinthifolia seedlings subjected to irrigation intervals. The experiment was performed by 78 days, under four irrigation intervals: 0, 4, 8, and 12 days, in combination with four concentrations SA: 0, 50, 100, and 200 mg L-1. The irrigation was individually maintaining water retention capacity of 100%, under each irrigation intervals. The maximum height across the irrigation intervals was 24.74 cm at 7-days intervals, and 24.31 cm with 200 mg L-1 of SA. The largest leaf areas were 116.03 cm2 at 12-day interval and 123.71 cm2 with 200 mg L-1 of SA. The highest production of dry masses of leaves, stem and roots was without and 12-days intervals, both with 200 mg L-1 of SA. Exogenous application of 200 mg L-1 of SA contributed on increased growth in S. terebinthifolia seedlings subjected to 12-days irrigation interval.

Resumo O uso de tecnologias alternativas que envolvem processos biológicos, com ganhos econômicos e ecológicos, é desejável para a expansão da bananicultura e a renovação de áreas que apresentam baixas produtividades. Os fungos micorrízicos arbusculares (FMAs) têm a capacidade de estimular o crescimento das plantas, especialmente por meio do incremento na absorção do fósforo (P) e de outros nutrientes. Objetivou-se, neste trabalho, verificar a influência dos FMAs sobre o crescimento e a fisiologia de mudas micropropagadas de bananeira submetidas a doses de P. O delineamento experimental adotado foi o de blocos casualizados, em arranjo fatorial 5 x 5, sendo os fatores inoculação com os FMAs (Glomus clarum, Gigaspora margarita, Gigaspora albida e Clareoideoglomus etunicatum e o controle sem FMAs), e cinco doses de P (0; 50; 100; 200 e 400 mg kg-1), com quatro repetições. A aplicação de doses de P proporcionou maior crescimento das mudas micropropagadas de bananeira, independentemente da inoculação micorrízica. As maiores taxas de colonização micorrízica foram observadas nas menores doses de P, sendo a dose de 50 mg kg-1 de P a que proporcionou melhores condições na formação de micorrizas para todas as espécies de FMAs avaliadas. As simbioses com FMAs e o uso de P proporcionaram aumento da taxa de fotossíntese das plantas, favorecendo o crescimento, o desenvolvimento e a qualidade de mudas de bananeira.

Abstract The use of alternative technologies involving biological processes, with economic and ecological gains, is desirable for both the expansion of Musa spp. farming and the renovation of areas with low yields. Arbuscular mycorrhizal fungi (AMF) can stimulate plant growth, especially by increasing the absorption of phosphorus (P) and other nutrients. This study analyzes the influence of AMF on the growth and physiology of micropropagated Musaspp. plants submitted to doses of P. The experimental design was randomized blocks, in a 5 x 5 factorial arrangement, in which the factors were inoculation with AMF (Glomus clarum, Gigaspora margarita, , Gigaspora albida,Clareoideoglomus etunicatum, and the control without AMF) and five doses of P (0, 50, 100, 200, and 400 mg kg-1), with four replicates. The application of P doses increased growth in micropropagated Musaspp. seedlings, regardless of mycorrhizal inoculation. The highest rates of mycorrhizal colonization occurred at the lowest P doses, and the dose of 50 mg kg-1 P provided better conditions for mycorrhizal formation in all AMF species under study. The symbioses with AMF, as well as the use of P, increased photosynthesis rate, thus favoring the growth, development, and quality of Musa spp. seedlings. Species G. clarum, C. etunicatum, and G. margarita were the most promising for plant growth.

Abstract In this study, we assessed the gas exchange in Caryocar brasiliense seedlings in water deficit conditions and their capacity to recover after rehydration. We assessed plant photosynthetic rates, internal carbon concentrations, stomatal conductance, transpiration rates, water-use efficiency, instantaneous carboxylation efficiency, chlorophyll index, and photosystem II quantum efficiency. All gas exchange parameters were reduced after the suspension of irrigation. Seedling photosynthetic rates approached zero after 12 days. The equilibrium was reestablished in all variables 11 days after re-initiating irrigation, with the exception of internal CO2 concentration and stomatal conductance. Exposure of seedlings to water stress resulted in drastically reduced photosynthetic processes. This reduction occurred due to the limitation of stomatal conductance and low rubisco carboxylation efficiency but not to irreversible damage photosystem II. All of these parameters demonstrated recuperation with rehydration, but only the photosynthetic rates reached initial control values.

Abstract The present work evaluated the physical-anatomical and initial growth of Tabebuia roseoalba seedlings exposed to different water regimes. The seedlings were grown under 100, 50, 25 and 12.5% of the water retention capacity (WRC). After 90 days, the following aspects were evaluated: height, diameter, fresh and dry weights of aerial and root, root length, and leaf area, Dickson quality index, liquid assimilation rate, relative growth rate, specific leaf area, stomatal index, and number of trichomes and leaf epidermal cells. The results indicated seedlings have greater initial growth and quality when cultivated at 100% WRC, and 25 and 12.5% WRC represented stress conditions for the plants. The species is hypostomatous with anomocytic stomata. The number of stomata, the stomatal index, and the number of epidermal cells did diminish with reduced water availability. The number of trichomes were larger on the adaxial face as water availability decreased.

Pereskia aculeata Plum. (Ora pro nóbis, Cactaceae) é uma planta de interesse medicinal e de valor alimentício por apresentar elevadores teores de fibras e proteínas. Porém, são incipientes informações referentes aos aspectos fisiológicos na fase de crescimento inicial de mudas. Assim, objetivou-se com este trabalho conhecer o metabolismo fotossintético de mudas de P. aculeata propagadas por estaquia sob contrastes de irradiância. O experimento foi desenvolvido sob duas disponibilidades luminosas (Pleno sol e sombreamento de 50%), avaliando-se os tipos de estaca apical, mediana e basal. O arranjo experimental foi em esquema fatorial 2 x 3, no delineamento blocos casualizados, com quatro repetições. Foram quantificados os pigmentos fotossintéticos, emissão da fluorescência da clorofila a e trocas gasosas. Constatou-se que os maiores teores de clorofilas e eficiências fotoquímicas ocorreram nas mudas de estacas apicais cultivadas sob 50% de sombreamento (baixa irradiância). As maiores taxas de assimilação de CO2, eficiência da Rubisco e de uso da água foram constatadas quando utilizadas estacas medianas e basais sob pleno sol (alta irradiância). A propagação por estacas medianas mantidas em alta ou baixa irradiância e basais em alta irradiância propiciaram maior capacidade fotossintética das mudas e podem ser indicadas para a propagação dessa espécie.

Pereskia aculeata Plum. (Ora pro nóbis, Cactaceae) is a plant of medicinal interest and alimentary value to present high contents of fibers and proteins. However, information regarding the physiological aspects in the initial growth stage of seedlings is incipient. Thus, the aim of this work was to know the photosynthetic metabolism of P. aculeata seedlings propagated by cuttings under irradiance contrasts. The experiment was conducted under two light conditions (full sun and 50% shading), evaluating the types of apical, median and basal cuttings. The experimental arrangement was in a 2 x 3 factorial scheme, in the randomized complete block design, with four replications. Photosynthetic pigments, chlorophyll-a fluorescence emission and gas exchange were quantified. Results showed that the highest levels of chlorophylls and photochemical efficiencies were observed in the apical cuttings cultivated under 50% shading (low irradiance). The highest rates of CO2 assimilation, Rubisco efficiency and water use were observed when using median and basal cuttings under full sun (high irradiance). The propagation by median cuttings maintained in high or low irradiance, and basal cuttings under high irradiance provided a greater photosynthetic capacity of the seedlings, and may be indicated for the propagation of this species.

RESUMEN Lippia alba (Mill.) N.E.Br. (hierba de limón) es una especie de interés medicinal y aromática, con estudios incipientes en relación a la nutrición mineral y a la luminosidad en las respuestas foliares y vegetativas. El objetivo del trabajo fue evaluar los aspectos foliares y la producción de plántulas de L. alba bajo dos condiciones de luminosidad (pleno sol y 50% de sombreamiento) y cuatro niveles de fósforo (0, 150, 300 y 450 mg kg-1). Las plántulas presentaron alteraciones en los índices fisiológicos y respuestas fotoquímicas basadas en la fluorescencia de la clorofila-a. La fertilización fosfatada contribuyó en la mitigación del estrés luminoso en la síntesis de clorofilas. La mayor pro ducción de biomasa de las hojas ocurrió con la adición de P. El análisis de componentes principales explicó el 74% de la variabilidad donde fueron características representativas el número de hojas, la fluorescencia inicial y el área foliar específica dentro del componente principal 1 (PC 1) y el número de brotes, supervivencia y el área foliar en el PC 2. En el análisis de conglomerados, se constató la formación de dos grupos, con distancias más bajas entre 300 pleno sol y 450 sombreamiento (2.31). Las plántulas cultivadas a pleno sol presentaron mayor capacidad de supervivencia y calidad. La producción de plántulas de L. alba debe ser realizada bajo pleno sol con adición de 450 mg kg-1 del fósforo.

ABSTRACT Lippia alba (Mill.) N.E.Br. (lemongrass) is a spice and medicinal plant species, with fledgling studies related to mineral nutrition and luminosity on foliar and vegetative responses. Thus, the aim of this study was to assess the foliar aspects and production of L. alba under two light conditions (full sun and 50% shading) and four levels of phosphorus-P (0, 150, 300 and 450 mg kg-1). The L. alba seedlings presented changes in physiological indices and photochemical responses based on chlorophyll-a fluorescence. The phosphate fertilization helped mitigate the light stress for the synthesis of chlorophylls. The greatest leaf biomass production occurred with addition of P. The principal components analysis explained 74% of the variability, with leaf number, initial fluorescence and specific leaf area in principal component 1 (PC 1) and bud number, survival and leaf area in PC 2. Two groups formed in the cluster analysis, with lower distances between P300 full sun and P450 sha ding (2.31). The seedlings cultivated under full sun presented a higher survivability and seedling quality. The production of L. alba seedlings should be done under full sun with the addition of 450 mg kg-1 of phosphorus.