To quantify water stress on coffee trees, leaf water potential (LWP) measurements are commonly performed in a Scholander chamber; however, this methodology is restricted to research activities, due to the difficulty of measurement in the field: sampling hours at predawn and intensive work. A crop water stress index (CWSI) based on leaf temperature has been used as indicative of LWP in several crops, and thermal images can be a precious tool for mapping LWP under intensive drip‐irrigated coffee areas, in order to adjust irrigation requirements according to soil moisture spatial variability. This study aims to define the relationships between the water potential of coffee leaf based on CWSI, calculated by means of a portable infrared sensor and a thermal camera, analysing correlation, precision and accuracy indexes. The study was conducted in Piracicaba, SP, Brazil, using Coffea arabica species of the Catuaí Red variety IAC 144 that was drip irrigated using tensiometers as matric potential sensors. The observed CWSI and LWP presented good correlations in the linear and cubic models. It was concluded that the CWSI is a good indicator of the water potential of a coffee canopy and can be an alternative to measurements of LWP from the Scholander chamber. © 2020 John Wiley & Sons, Ltd.

Awareness of evapotranspiration (ET) and crop coefficient (K c) is necessary for irrigation management in coffee crops. ET and K c spatial variabilities are disregarded in traditional methods. Methods based on radiometric measurements have potential to obtain these spatialized variables. The K c curve and spatial variability of actual evapotranspiration (ET a) were determined using images from Landsat 8 satellite. We used images of young and adult coffee plantations from OLI (Operational Land Imager) and TIRS (Thermal Infrared Sensor) sensors over a two-year period. Evapotranspiration was estimated using the Surface Energy Balance Algorithm for Land (SEBAL). Moreover, the reference evapotranspiration (ET o) was estimated through the Penman-Monteith method. We obtained the values for the evapotranspiration fraction (ET f), analogous to K c , according to ET and ET o values. The study was conducted in Buritis, Minas Gerais State, Brazil, in areas cropped with Coffea arabica irrigated by central pivots. A comparative analysis was made using different statistical indices. Average ET a was 2.17 mm d-1 for young coffee plantations, , and the K c mean value was 0.6. For adult coffee plantations, average ET a was 3.95 mm d-1 , , and the K c mean value was 0.85. The ET c and K c data obtained based on the SEBAL algorithm displayed similar values to studies that used traditional methods. This model has huge potential to estimate ET of different stages of coffee plantation for the region studied.

The plant water potential and the leaf temperature are physiological responses of the coffee tree that can be used as indicative of the irrigation management of this crop. There is a dependence between the leaf water potential with the potential matrix of the soil solution, however, the water potential levels found for the coffee tree show divergent relationships in the literature regarding the matrix potential. The objective of this study is to verify the water potential and leaf surface temperature in the coffee tree when submitted to different irrigation levels. The study was conducted in Piracicaba, SP, Brazil, using Coffea arabica species from Red Catuaí IAC 144 variety, the drip irrigation system was adopted and the management done by tensiometry. The relationships among these physiological responses and the treatments of actions presented high determination coefficients (R² of 0.84, 0.90 and 0.65 for the leaf water potential, leaf temperature measured with the portable infrared sensor and the thermal camera respectively). The estimated values for leaf water potential were-0.23,-0.56,-0.89 and-1.22 MPa for irrigation treatments L130%, L100%, L70% and L40%, respectively. The calculated leaf temperature values were 31.7, 32.4, 33.0 and 33.7°C in average, for treatments L130%, L100%, L70% and L40% in proper order.

RESUMO:Clones de seringueira (Hevea spp ) são enxertados sobre porta-enxertos oriundos de sementes de ascendência desconhecida e por isto não exteriorizara todo seu potencial genético de produção de látex. A superação desta dificuldade pode ser obtida com o enraizamento de estacas clonais. Todavia, a seringueira é considerada em seu estágio adulto como uma planta de difícil enraizamento. Estas plantas possuem na base do caule um cilindro quase contínuo de tecidos lignificados, que juntamente com barraras químicas podem dificultar o enraizamento. Atualmente, algumas plantas de difícil enraizamento, têm enraizado com a ajuda de um conjunto de técnicas modernas como estiolamento total ou localizado e estrangulamento. Este trabalho, procurou caracterizar as modificações que ocorrem em estacas clonais de seringueira submetidas àquele conjunto de técnicas. Pode-se concluir que o estrangulamento da base de estacas do clone RRIM 600, assim como sua utilização em conjunto com os dois tipos de estiolamento, promoveu alterações na atividade do câmbio vascular que produziu maior número de células parenquimáticas no floema, resultando na descontinuidade da bainha de fibras perivasculares, o que representa um indício para o favorecimento ao enraizamento das estacas. Descritores: Hevea brasiliensis, estacas, raízes adventícias, anatomia ANATOMICAL CHANGES IN RUBBER TREE CUTTINGS (Hevea brasiliensis CLONE RRIM 600) IN RESPONSE TO DIFFERENT ROOTING TECHNIQUESABSTRACT: Clones of Hevea spp are presently grafted on seedlings, because no economic method of producing clonal rootstocks by vegetative means or clonal cuttings has so far been discovered. Because of this, Hevea clones do not exteriorize their maximum genetic potential for latex production. The rooting of clonal cuttings overcomes this problem. However, Hevea is considered a plant with very poor capacity of rooting, in its mature phase. Plants have at the stem base an almost continuous cylinder of lignified tissues, which along with chemical barriers can difficult rooting. At present, rooting problems in some plant species may be overcome by a combination of new techniques as it is the case of total or local etiolation and girdling. This work has the aim to characterize the modifications occurred in clonal cuttings of Hevea when subjected to the above mentioned techniques, alone or combined. It was possible to conclude that the girdling of the cutting base from the RRIM 600 clone, as well as its utilization in combination with the other two types of etiolation, promoted drastic alterations in the sheath, as compared to the control. Moreover, girdling promoted the activity of the vascular cambio, which produced a greater number of parenquimatous cells in the phloem, resulting in a discontinuity, of the perivascular fibers sheath. Other alterations elapsed of the girdling were: the division of parenquimatous cells around of the sheath forming meristematic rings and a greater number of lenticells in comparison to the control, which can favor the rooting of the cuttings.

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The leaf area index (LAI) is relevant in studies of phenomena at different scales, such as for the leaf to canopy scale and the calculation of the extinction coefficient of photosynthetically active radiation (kPAR), providing input for the parameterization of physiological basis models. The objective of this work was to verify the variation of the LAI and the coffee kPAR subjected to different drip irrigation levels (130, 100, 70, and 40%) and to compare the data obtained from radiation bar linear sensors (SunScan) in the plants that received full irrigation with the values found by other LAI estimation methodologies. The study was conducted in Piracicaba, São Paulo State, Brazil, using the species Coffea arabica cv. Red Catuaí IAC 144; a drip irrigation system was adopted, with the irrigation controlled by tensiometry. The mean LAI values were higher in the L130 (irrigation level of 130%) and L100 (irrigation level of 100%) treatments than those with deficit irrigation depths. The mean kPAR values were lower for the L130 and L100 treatments than the values found in the deficit irrigation depth treatments. When comparing SunScan to other methodologies, the mean error (ME) and absolute mean error (AME) were high.

RESUMO: -Visando determinar os efeitos do espaçamento entre linhas (30, 40 e 50 cm) e da densidade de semeadura (50, 100 e 150 sementes/m 2 ) sobre o rendimento de grãos e algumas características biométricas de duas variedades de arroz (Oryza sativa L.), com e sem irrigação suplementar, foram conduzidos quatro experimentos em solo de cerrado, sendo dois com a variedade Araguaia e os outros com a 'Guarani'. A irrigação propiciou incremento de 90 e 35% no rendimento de grãos das v. Araguaia e Guarani, respectivamente, influenciando significativamente todas as características biométricas estudadas. A v. Guarani apresentou maior produção de grãos no menor espaçamento e na densidade de 130 sementes por m 2 , e o seu índice de colheita (IC) foi correlacionado linear e positivamente com o rendimento de grãos. Na v. Araguaia, o maior rendimento de grãos foi observado no espaçamento de 40 cm, independente da irrigação e da densidade de semeadura. A 'Guarani' mostrou ser uma variedade mais competitiva que a 'Araguaia', apresentando menor IC e maior influência da densidade de semeadura, sobre o rendimento de grãos. Descritores: Oryza sativa, espaçamento entre linhas, densidade de semeadura, rendimento, características biométricas, irrigação BEHAVIOUR OF UPLAND RICE VARIETIES AT DIFFERENT PLANT DENSITIES, UNDER AND WITHOUT SUPPLEMENTAL IRRIGATIONABSTRACT: Four experiments were carried out in a cerrado soil to study the effect of row spacing and seed density on rice (Oryza sativa) yield and some byometric characteristics, with and without supplemental sprinkler irrigation. Two experiments used the Araguaia variety and the other two, the Guarani variety. Irrigation enhanced in 90 and 35% the yield of the varieties Araguaia and Guarani, respectively. Irrigation significantly affected biometric characteristics. The highest yield of Guarani v. was obtained with 30 cm row spacing and density of 130 seeds per m 2 , and its harvest index (HI) was linearly and positively correlated with grain yield. The highest yield of Araguaia v. was obtained with 40 cm spacing, independently of the density and presence of irrigation. The variety Guarani showed to be more competitive than the Araguaia, having smaller HI and its grain yield being more affected by plant population. Key Words: Oryza sativa, row spacing, seed density, grain yield, biometric characteristics, irrigation INTRODUÇÃOCerca de 50% da produção brasileira de arroz provém do sistema de cultivo de sequeiro. Neste sistema, são reconhecidas duas situações distintas em termos de risco de ocorrência de deficiência hídrica. As regiões com menor e maior risco foram caracterizadas como favoráveis e não favoráveis, respectivamente, para o cultivo de arroz (STEINMETZ et al., 1984).Em áreas sujeitas à ocorrência de veranico, são observados freqüentes insucessos, ocasionando baixos rendimentos, o que tem desestimulado os produtores a utilizarem tecnologias adequadas. Com isso, o produtor limita seus investimentos, permanecendo num baixo nível de utilização de 1 Parte da tese de Doutorado a...

• Sete Lagoas, MG 3 Depto. de Agricultura da ESALQ/USP -CP. 9-CEP: 13418-900 -Piracicaba, SP RESUMO: O presente trabalho tere por objetivo avaliar as relações entre fonte de assimilados e grão-dreno, bem como o comportamento de fatores morfo-fisiológicos que limitam o rendimento de grãos em plantas de milho de diferentes ciclos (normal, precoce e superprecoce), cultivadas em semeadura tardia (safrinha), com três densidades (33 mil, 55 mil e 77 mil plantas/ha). Verificou-se a eficiência de híbridos de milho quanto à duração do crescimento e rendimento, nas fases vegetativa e reprodutiva. Os rendimentos em grãos variaram entre os híbridos e entre as densidades e foram significativamente superiores nas maiores densidades de cultivo, para os três híbridos avaliados. Valores máximos de índice de área foliar, dentro de híbrido, resultaram em maiores rendimentos de grãos e contribuíram para explicar a variação do acúmulo de matéria seca total e do grão. Todos os híbridos tiveram o enchimento de grãos incompleto, indicando inadequada oferta de assimilados durante essa fase, principalmente para o híbrido superprecoce. Isto sugere que a oferta foi inferior à capacidade de armazenamento na espiga e, nesse caso, além do rendimento de grãos, outros órgãos vegetativos ficaram prejudicados em seu desenvolvimento. As condições ambientais de cultivo de safrinha são subótimas para o desenvolvimento do milho, principalmente para os híbridos com características e comportamento de precocidade acentuada. Descritores: Zea mays L., híbridos, ciclos, densidade, safrinha, grão-dreno. ECOPHYSIOLOGICAL FACTORS AFFECTING MAIZE BEHAVIOUR OF LATE SUMMER PLANTING IN CENTRAL BRAZILABSTRACT: The objective of this work was to evaluate the source-sink relationships, as well as the effects of morphophysiological factors that limit the grain yield of maize plants of different cycles (normal, early and very early) planted in late summer ("safrinha"). This trial included three plant populations (33, 55 and 77 thousand plants/hectare). Hybrid efficiencies related to duration of growth and yield were evaluated, in the vegetative and reproductive phases. The grain yield varied among hybrids and populations, and the best yields were found in the highest plant population for all hybrids. The maximum values for leaf area index within hybrids resulted in high grain yields and contributed greatly to total dry matter accumulation in the plant and grain. All the hybrids had incomple grain filling, which indicates low offer of assimilates during this stage, especially for very early hybrids. This suggests that the source was lower than the capacity of the sink and in this case, besides grain yield, other vegetative parts were injured in their development. Environmental conditions for cultivating in late summer are not the best for the development of the maize plant, mainly for hybrids of very early cycle.