Plants growing in temperate regions are often exposed to stress conditions caused by high temperatures. Photosynthesis is one of the metabolic processes most sensitive to high temperature stress, and it is often inhibited before other cellular functions. Using peach leaf disks, we studied the transient chlorophyll a fluorescence along with the gas exchanges at temperatures of 25 (control)
RESUMO -A espécie Solanum americanum (maria-pretinha) é considerada planta daninha; por possuir elevada habilidade competitiva e agressividade, ela reduz a produtividade dos cultivos. O trabalho foi conduzido em casa de vegetação e objetivou analisar o crescimento e a partição de assimilados em plantas de maria-pretinha submetidas a três níveis de sombreamento. As plantas foram coletadas em intervalos regulares de sete dias após o transplante até o final do ciclo, sendo determinada a massa seca e a área foliar. A partir dos dados primários, foi aplicada a análise de crescimento, sendo calculados a massa seca total (W t ), as taxas de produção de matéria seca (C t ), crescimento relativo (R w ) e assimilatória líquída (E a ), o índice de área foliar (L), as razões de área foliar (F a ) e massa foliar (F w ), a área foliar específica (S a ), a partição de matéria seca entre órgãos e o número de frutos. Plantas de maria-pretinha cresceram e se desenvolveram melhor sob condição intermediária de luz (65%), em que atingiram maior W t , C t , L, F a, matéria seca de caule, matéria seca de fruto e maior número de frutos, enquanto a luz plena e a redução da luminosidade em nível acentuado, de maneira mais marcante, afetaram negativamente o crescimento e o desenvolvimento, o que possivelmente pode influenciar a habilidade competitiva da maria-pretinha.Palavras-chave: Solanum americanum, área foliar, matéria seca, taxas de crescimento.ABSTRACT -The species Solanum americanum (mary-nightshade) is considered a weed whose highly competitive ability and aggressiveness reduce crop productivity. This work was conducted under greenhouse conditions aiming to analyze the growth and partitioning of assimilates in marynightshade plants subjected to three levels of shading. The plants were collected at regular intervals of seven days after transplantation until the end of the cycle, with dry mass and leaf area being determined. Based on primary data , growth analysis was carried out to calculate total dry matter production (W t ), dry matter production rates (C t ), relative growth (R -w ), net assimilation (E a ), leaf area index (L), relative growth of leaf area and ratios of leaf area (F a ) and leaf mass (F w ), specific leaf area (S a ) and dry matter partitioning between organs. Mary-nightshade plants showed a better growth and development under intermediate light conditions (35% shade), reaching higher W t , C t , L, F a , stem dry matter, fruit dry matter and number of fruit. Full light and reduction of light at a more accentuated level had a negative effect on growth and development, a fact that may influence the competitive ability of these plants.
RESUMOA profundidade de semeadura pode interferir na emergência das plântulas e no seu estabelecimento inicial. Este trabalho objetivou avaliar a influência da profundidade de semeadura sobre a expressão do vigor de sementes e o desempenho inicial de plântulas de feijoeiro. Utilizaram-se sementes das cultivares IPR-Gralha e IPR-Tiziu e os tratamentos consistiram em diferentes profundidades de semeadura, 15; 30; 45 e 60 mm. Foram avaliados emergência, comprimento e matéria seca de raízes e parte aérea, área foliar, razão de parte aérea, raiz e área foliar. A emergência e a matéria seca das plântulas reduziram com a profundidade de semeadura. A razão de área foliar aumentou na cultivar IPR-Tiziu até a profundidade de 30 mm e na cultivar IPR-Gralha foi crescente com o aumento da profundidade de semeadura. O aumento na profundidade de semeadura reduz a expressão do vigor e o desempenho inicial de plântulas de feijoeiro.Palavras-chave: estande de plantas, performance de plântulas, Phaseolus vulgaris L., qualidade fisiológica Seed vigor and initial performance of bean seedlings under different sowing depths ABSTRACTThe sowing depth can influence the seedling emergence and its initial establishment. The aim of this study was to evaluate the influence of sowing depth on the expression of vigor and initial performance of bean seedlings. The cultivars used were IPRGralha and IPR-Tiziu and the treatments consisted of different sowing depths 15, 30, 45 and 60 mm. The parameters evaluated were emergence, seedling length (root and shoot), seedling dry weight (root and shoot), leaf area, shoot/root ratio and leaf area ratio. The emergence and seedling dry weight were reduced with the sowing depth. The leaf area ratio increased in the cultivar IPR-Tiziu until depth of 30 mm and in the cultivar IPR-Gralha increased with the depth of sowing. Increased sowing depth decreased the vigor expression and initial performance of bean seedlings.
O trabalho objetivou avaliar a influência da composição de um substrato organoarenoso sobre emergência e parâmetros fisiológicos de mudas de angico-branco. As sementes foram submetidas à germinação nas seguintes composições do substrato: T1) 100% areia; T2) 75% areia + 25% Tecnomax®; T3) 50% areia + 50% Tecnomax®, T4) 25% areia + 75% Tecnomax®; T5) 100% Tecnomax®. As avaliações foram efetuadas aos 45, 90, 135 e 180 dias após a semeadura (DAS), sendo aferidos a altura de parte área e o diâmetro do coleto. Aos 180 DAS determinou-se a massa seca de parte aérea e de raiz, a massa seca total e os teores de clorofila a, b e total. A composição T1 (100% areia) proporcionou maior altura em mudas de angico nas quatro épocas de avaliação. A massa seca da parte área e de raiz foi superior na composição T2 aos 180 DAS, assim como a massa seca de raiz, o mesmo foi obtido para o índice de qualidade de Dickson (IQD). Os teores de clorofila apresentaram modificação quali-quantitativa de acordo com a composição do substrato. A expressão do vigor da semente de angico-branco é afetada pela composição do substrato, sendo superior em substratos cuja composição contenha areia. A combinação entre Tecnomax® e areia constitui substrato organoarenoso, com potencial de emprego para produção de mudas de angico-branco.
abstractthis study aimed to evaluate the effect of flooding and water restriction (drought) on the photosynthetic activity in plants of the hybrid rootstock 'GxN-9' (Prunus dulcis Mill. × Prunus persica l. Bastsch), grown in a greenhouse. chlorophyll fluorescence and gas exchange were analyzed in plants of approximately 12 months. the reduction of photosynthetic activity in both the stresses were associated with decreased carboxylation efficiency, but without affecting the internal concentration of carbon dioxide. the JiP-test parameters revealed changes in the energy flux processes demonstrating that in terms of flooding the rootstock GxN-9 the rate of photosynthetic performance significantly decreases, resulting in a considerable decrease in net assimilation rate. the JiP-test analysis was efficient in determining the thresholds mainly of the flood response, proving to be useful in exploration of the photosynthetic activity as a physiological marker of the stress tolerance.
R E S U M OO pinhão-manso (Jatropha curcas L.) tem-se destacado, no cenário do biodiesel, em função da porcentagem de óleo contido nas sementes e de sua capacidade adaptativa. No País, a cultura do pinhão-manso tem, como proposta, o desenvolvimento agronômico, razão pela qual o uso consorciado pode ser importante aos pequenos produtores. Este trabalho teve como objetivo avaliar algumas características fenológicas de pinhão-manso cultivado em dois regimes de luminosidade (pleno sol e sombrite 50%) relacionando com a sazonalidade climática e se utilizando de parâmetros da fluorescência da clorofila e de trocas gasosas. As plantas apresentaram crescimento vegetativo com padrão sazonal, com pico de crescimento no início de março, quando iniciou a senescência foliar. Alguns parâmetros da fluorescência transiente da clorofila analisados pelo Teste JIP, apresentaram relação com as flutuações ambientais. O PI ABS e o PI total demonstraram que as plantas do tratamento sombreado foram sensíveis à redução de luminosidade. A taxa assimilatória líquida e a eficiência de carboxilação reduziram ao longo do experimento acompanhando a queda da radiação solar; já as plantas de pinhão-manso respondem negativamente a essas condições de sombreamento. Growth and photosynthesis of Physic nut grown under different light conditions A B S T R A C TJatropha curcas L. has been prominent in the scenario of biodiesel due to the percentage of oil contained in the seeds and its adaptive capacity. The cultivation of J. curcas in the country has as proposal the agronomic development and its consortium may be important for small producers. This study aimed to characterize the phenological behavior of J. curcas grown under different light conditions, full sun and 50% shade, relating them to the climatic seasonality, comparing their development with chlorophyll a fluorescence and gas exchange. Plants showed vegetative growth with seasonal pattern, with growth peak at the beginning of March, when the leaf senescence began. The analysis of the kinetic of the transient fluorescence of chlorophyll presented a relationship between certain parameters of the test JIP and the environmental fluctuations. The PI ABS and the PI total demonstrated that in the shaded treatment plants were sensitive to luminosity reduction. The liquid assimilation rate and the carboxylation efficiency decreased throughout the experiment, accompanying the decline of the solar radiation. J. curcas plants respond negatively to these shaded conditions. Crescimento e fotossíntese de plantas de pinhão-manso cultivadas em diferentes condições de luminosidade
This study aimed to evaluate the growth, assimilate partitioning and seed vigor expression of rye seeds subjected to waterlogging during development. The experimental design was completely randomized with six replications and three treatments. The treatments involved different waterlogging periods: a) no waterlogging; b) single waterlogging of three days; and c) two soil waterlogging periods of three days. The plants were collected at regular intervals of 14 days after emergence until the end of the growth cycle, measuring the dry matter accumulation and the leaf area for growth analysis and dry matter partition between the organs and number of flowers. The other calculated indices included the harvest index and relative seedling emergence rate originating from the seeds of plants that were maintained at field capacity and under the effect of soil waterlogging. Rye plants that were not subjected to waterlogging had a higher dry matter, dry matter production rates and harvest index compared to the plants under the effect of two soil waterlogging periods. Plants under the effect of two waterlogging periods showed drastic alterations in their growth rates and assimilate partitioning during development, and seed vigor expression was negatively affected when the plants were subjected to soil waterlogging.
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