ABSTRACT. Sunflower growth is adversely impacted by both excess and insufficient water. Research on root growth in this crop under water stress conditions remains limited and does not fully elucidate the plant's response to varying soil and climatic conditions. This study aimed to determine root growth, depth, and distribution of sunflower plants under different water stress conditions, such as deficit or excess, in two soil classes and sown during two distinct periods. Experiments were conducted after sowing at the beginning of September (first crop season) and at the beginning of January (second crop season) in an Ultisol (Santa Maria, Rio Grande do Sul State, Brazil) and an Oxisol (Panambi, Rio Grande do Sul State, Brazil). Water condition treatments applied from stage V6 included control, water deficit, and water excess. Roots were collected using an auger drill during the first crop season. The variables analyzed comprised root length density and accumulated root within the soil profile. During the second crop season, sunflower roots were visually assessed in the soil profile after trench excavation. Root system depth and root dry mass were evaluated during both sowing periods. Results indicated that sunflower root penetration is deeper in Ultisol than in Oxisol. Water deficit promotes root depth, while water excess promotes root growth near the surface. Sowing during the first crop season results in deeper root penetration and higher root dry mass production compared to the second crop season. ABSTRACT plant s periods Santa Maria State Brazil Panambi, Panambi (Panambi Brazil. . V control excavation surface

ABSTRACT. Waterlogging directly interferes with the production capacity of agricultural crops in response to the morphophysiological changes caused to plants. Since the cultivation of poorly drained soils is traditionally avoided, this study aimed to evaluate the possibility of expanding canola cultivation into waterlogged soils using soil surface drainage and different row spacings in lowland areas of Rio Grande do Sul, Brazil. Treatments consisted of the presence and absence of surface drains at 0.25 m depth and row spacings of 0.17, 0.34, 0.51, and 0.68 m arranged in two-factorial randomized blocks with four replications, in 2018 and 2019. In this study, growth traits, yield components, and the final grain yield of canola were evaluated. The increase in lateral branching in canola plants was found to be directly related to waterlogging and negatively affected yield. The use of drains positively impacted the number of pods per plant, seeds per pod, the 1,000 seeds weight, and grain yield. The more intense waterlogging conditions in 2018 resulted in the highest grain yield and superior production traits were obtained with row spacings between 0.41 and 0.48 m. In the absence of waterlogging, the 0.17 m row spacing was more productive. Canola cultivation can occur in waterlogged soils in the presence of surface drainage and at row spacings ranging from 0.40 to 0.50 m. ABSTRACT avoided Sul Brazil 025 0 25 0.2 017 17 034 34 0.34 051 51 0.51 068 68 0.6 twofactorial two factorial replications 201 2019 components evaluated plant pod 1000 1 000 1,00 weight 041 41 0.4 048 48 0.1 productive 040 40 050 50 0.5 02 2 0. 01 03 3 0.3 05 5 06 6 20 100 00 1,0 04 4 10 1,

Resumo O objetivo desse estudo foi determinar a duração média e a variabilidade interanual dos subperíodos fenológicos e do ciclo total de desenvolvimento da soja para 11 datas de semeadura em condições de clima subtropical úmido do estado do Rio Grande do Sul. Foram utilizados dados meteorológicos diários de 1971 a 2017 da estação agroclimatológica de Pelotas e de 1968 a 2017 da estação climatológica principal de Santa Maria. A simulação do desenvolvimento da soja foi realizada considerando-se três conjuntos de cultivares de grupo de maturidade relativa entre 5.9-6.8, 6.9-7.3 e 7.4-8.0, com intervalos entre as datas de semeadura de aproximadamente 10 dias compreendidas entre 21 de setembro e 31 de dezembro. Os dados de duração dos subperíodos fenológicos e do ciclo total de desenvolvimento foram submetidos à análise exploratória BoxPlot, análise de variância e comparação de médias pelo teste de Scott-Knott, a 5% de probabilidade. A duração do ciclo de desenvolvimento é maior em Pelotas do que em Santa Maria. Houve decréscimo da duração do ciclo da soja da primeira para a última data de semeadura para ambos os locais. Devido à redução do fotoperíodo, a duração do subperíodo R1-R5 é decrescente de outubro até dezembro.

Abstract The objective of this study was to determine the mean duration and the interannual variability of phenological subperiods and total soybean development cycle for 11 sowing dates in the humid subtropical climate conditions of the state of Rio Grande do Sul. Daily meteorological data were used from 1971 to 2017 obtained from the Pelotas agroclimatological station and from 1968 to 2017 from the main climatological station of Santa Maria. The soybean development simulation was performed considering three sets of cultivars of relative maturity groups between 5.9-6.8, 6.9-7.3 and 7.4-8.0, with intervals between the sowing dates of approximately 10 days, comprising September, 21 to December, 31. The data of phenological subperiods duration and total development cycle were subjected to the exploratory analysis BoxPlot, analysis of variance and mean comparison by the Scott-Knott test, with 5% of probability. The development cycle duration is greater in Pelotas than in Santa Maria. There was a decrease in soybean cycle duration from the first to the last sowing date for both locations. The R1-R5 subperiod duration is decreasing from October to December due to photoperiod reduction.

Resumo O objetivo deste trabalho foi obter uma metodologia de cálculo do balanço hídrico sequencial que estime com acurácia a ocorrência de excesso hídrico na soja em terras baixas. Foram testadas quatro estratégias de cálculo do balanço hídrico associadas à simulação do desenvolvimento da soja, as quais se diferenciaram em função da forma de cômputo da chuva e do tempo de drenagem da água dos macroporos do solo. Como referência foram utilizados os dados de umidade volumétrica monitorada em três camadas de solo ao longo do ciclo da soja no ano agrícola 2014/15. A microporosidade foi utilizada como limite inferior da ocorrência de excesso hídrico na área. Assim, o excesso hídrico foi considerado sempre que a umidade volumétrica diária do solo na camada 0-100 mm foi maior que 0,39 mm³ mm-3. Ao longo dos 111 dias de medição, a umidade do solo indicou a presença de excesso hídrico em 38 dias. A estratégia de cálculo tradicional do balanço hídrico subestimou a ocorrência de excesso hídrico, assim como as demais estratégias que consideraram a precipitação efetiva na sua metodologia. A estratégia de cálculo que considera que toda a chuva infiltra no solo e que a água dos macroporos é removida somente pela evapotranspiração da cultura apresentou bom desempenho e indicou 35 dias de excesso hídrico, sendo a mais adequada e recomendada para a determinação do excesso hídrico na soja em terras baixas.

Abstract The aim of this study was to derive a methodology for calculating a sequential water balance that accurately estimates the occurrence of excess water in soybeans cultivated in lowlands. We tested four calculation strategies of water balance associated with the simulation of soybean development, which differed on the calculation of rainfall and time of water drainage from the soil macropores. Data of volumetric moisture monitored in three soil layers throughout the soybean cycle in the 2014/15 agricultural year were used as a reference. Microporosity was used as a lower limit for the occurrence of excess water in the area. Excess water was considered to be whenever the daily volumetric soil moisture in the 0-100 mm layer was greater than 0.39 mm3 mm-3. Over the 111 days of measurement, soil moisture indicated the presence of excess water in 38 days. The traditional calculation strategy of water balance underestimated the occurrence of excess water, as well as the other strategies that considered effective precipitation in their formulas. The calculation strategy that considers that all the rainfall infiltrates in the soil and that the water from macropores is removed only by crop evapotranspiration exhibited good performance and indicated 35 days of excess water, being the most appropriate and recommended for determining excess water in lowland soybeans.

Abstract Brown leaf spot disease, caused by the fungus Ragnhildiana diffusa, is responsible for losses in pecan orchards and quantification is essential in order to conduct epidemiological studies to establish levels of productivity losses, and assess control strategies. Therefore, the aim of this study was to develop and validate a diagrammatic scale for assessing the severity of brown leaf spot in pecan. 240 symptomatic leaflets were collected from adult trees in Anta Gorda, in the Brazilian state of Rio Grande do Sul, and used to assess the current percentage severity of the disease. The scale was based on the minimum and maximum observed severity of the disease, with six graduations defined according to the Weber-Fechner Visual Stimulus Law. The scale therefore consisted of eight levels (1.5, 4.6, 10.6, 17.3, 39.5, 65.1, 77.5, and 98%). The estimates of eight evaluators provided a basis for validating the scale. They made estimates of disease severity on 40 symptomatic digitalized pecan leaflets first, without using the scale and then referring to it. The scale provided greater precision, accuracy, and reproducibility of estimates and should result in more reliable epidemiological studies.

RESUMO: O objetivo deste trabalho foi identificar as datas de semeadura com menor risco de ocorrência de excesso hídrico para a cultura da soja, em um Planossolo Háplico na Depressão Central do Rio Grande do Sul. A simulação do desenvolvimento da soja e o balanço hídrico sequencial diário foram realizados para diferentes datas de semeadura em cada ano do período de agosto de 1968 a julho de 2012. Os dados dos dias de excesso hídrico, obtidos para o ciclo da cultura, foram submetidos à análise BoxPlot e teste de Scott-Knott a 5% de probabilidade de erro. Foram testadas as funções exponencial, gama, lognormal, normal e weibull, verificando-se a de melhor ajuste aos dados obtidos para os subperíodos e ciclo total. O maior número de ajustes para o ciclo de desenvolvimento e para os subperíodos foram obtidos para as funções gama e weibull, respectivamente. As semeaduras, realizadas após o dia primeiro de novembro, apresentam menor risco de ocorrência de excesso hídrico no subperíodo semeadura-emergência. O risco de ocorrência de excesso hídrico para o ciclo de desenvolvimento é decrescente, conforme o avanço da data de semeadura.

ABSTRACT: The aim of this study was to identify soybean sowing dates on which there was low water surplus risk. The crop was raised on a Haplic Planosol soil in the Central Depression of Rio Grande do Sul, Brazil. Soybean development simulations and daily water balances were calculated for different sowing dates from August 1968 to July 2012. Water surplus data was subjected to BoxPlot analyses and Scott-Knott tests at a 5% error probability. Exponential, gamma, lognormal, normal and Weibull functions were tested and the best fits to the data were obtained for both subperiods and total cycle. The highest number of fits for the development cycle and subperiods were obtained using the gamma and weibull functions, respectively. For sowing carried out after November 1, there was a low water surplus risk in the sowing-emergence subperiod. The risk of water surplus during the development cycle decreased with the advance of the sowing date.

O objetivo deste trabalho foi identificar datas de semeadura com menor ocorrência média de dias com excedente hídrico para a cultura do girassol, e determinar a persistência de dias consecutivos com excedente hídrico ao se considerar a capacidade de armazenamento de água disponível de diferentes solos da região central do Rio Grande do Sul. O desenvolvimento da cultura e o aprofundamento do sistema radicular foram simulados de acordo com a soma térmica para 14 datas de semeadura, de agosto até meados de fevereiro, com dados de 1968 até 2011. A partir da capacidade de armazenamento de água disponível para as diferentes classes de solos da região, calculou-se o balanço hídrico sequencial diário para determinar os dias com excesso hídrico. Avaliou-se a ocorrência de dias com excesso hídrico em diferentes subperíodos de desenvolvimento da cultura, e procedeu-se à análise exploratória com gráficos box-plot para determinação da persistência de dias consecutivos com excesso hídrico durante todo o ciclo da cultura. O excedente hídrico limita o cultivo de girassol em determinadas áreas e períodos na região central do Rio Grande do Sul. A persistência de dias consecutivos com excedente hídrico e a duração do ciclo de desenvolvimento da cultura são influenciados pela data de semeadura.

The objective of this work was to identify sowing dates with the lowest average occurrence of days with water excess for sunflower crop, and to determine the persistence of consecutive days with water excess considering the available water storage capacity of different soils of the central region of the state of Rio Grande do Sul, Brazil. Crop development and root system deepening were simulated based on thermal summation for 14 sowing dates, from August until mid-February, with data from 1968 to 2011. From the available water storage capacity of the different soil classes of the region, the sequential daily water balance was calculated to determine the days with water excess. The occurrence of days with water excess was evaluated in different crop development sub-periods, and exploratory analysis with box-plot graphs was performed to determine the persistence of consecutive days with water excess during the crop cycle. Water excess limits sunflower cultivation in some areas and periods in the central region of the state of Rio Grande do Sul. The persistence of consecutive days with water excess and the duration of the crop development cycle are influenced by the sowing date.

O objetivo deste trabalho foi obter um modelo matemático que estime o índice de área foliar (IAF) para a cultura do girassol em função da soma térmica acumulada. A geração dos modelos e o teste de seus coeficientes foram realizadas com dados obtidos de experimentos conduzidos em diferentes datas de semeadura nos anos agrícolas de 2007/08, 2008/09, 2009/10 e 2010/11, com os híbridos de girassol Aguará 03 e Hélio 358. Utilizou-se as dimensões lineares das folhas para determinação não destrutiva da área foliar e a soma térmica para quantificar o tempo biológico. Conhecidos os dados de soma térmica acumulada (STa) e IAF para um mesmo dia após a emergência, gerou-se modelos matemáticos que estimam o IAF. Foram obtidos, por apresentarem os melhores ajustes (menor raiz quadrada do quadrado médio do erro, RQME), os modelos de pico gaussiano, polinomial cúbico, sigmoidal e um modelo ajustado composto, denominado sigmoidal modificado. O modelo sigmoidal modificado obteve melhor ajuste aos dados de geração e o maior valor do coeficiente de determinação (R2). No teste dos modelos obteve-se os menores valores da raiz do quadrado médio do erro e maior R2entre valores observados e estimados para o modelo sigmoidal modificado.

The aim of this study was to obtain a mathematical model for estimating the leaf area index (LAI) of a sunflower crop as a function of accumulated thermal time. Generating the models and testing their coefficients was carried out using data obtained from experiments carried out for different sowing dates in the crop years of 2007/08, 2008/09, 2009/10 and 2010/11 with two sunflower hybrids, Aguará 03 and Hélio 358. Linear leaf dimensions were used for the non-destructive measurement of the leaf area, and thermal time was used to quantify the biological time. With the data for accumulated thermal time (TTa) and LAI known for any one day after emergence, mathematical models were generated for estimating the LAI. The following models were obtained, as they presented the best fit (lowest rootmean- square error, RMSE): gaussian peak, cubic polynomial, sigmoidal and an adjusted compound model, the modified sigmoidal. The modified sigmoidal model had the best fit to the generation data and the highest value for the coefficient of determination (R2). In testing the models, the lowest values for root-mean-square error, and the highest R2 between the observed and estimated values were obtained with the modified sigmoidal model.

Foram determinados novos coeficientes do termo que pondera a nebulosidade na Equação de Brunt-Penman utilizando-se a razão de radiação solar (RK) no lugar da razão de insolação (n/N) e foram testados e ajustados coeficientes das equações do método de Brutsaert propostas para o período diurno no sul do Brasil e verificou-se qual das metodologias tem resultados mais corretos em relação à Equação de Brunt-Penman original, para Santa Maria/RS, para o período diário. Foram utilizados dados meteorológicos obtidos nas Estações Meteorológicas Automática e Convencional de Santa Maria em 2.472 dias. Os coeficientes foram ajustados pelo método de regressão linear ou não-linear, dependendo do modelo, utilizando-se 2/3 dos dados. As Equações ajustadas foram testadas com os demais 1/3 dos dados. A equação de Brunt-Penman modificada com o termo da nebulosidade ponderada tanto pela radiação solar incidente na superfície na ausência de nebulosidade (RK,R) como pela radiação solar incidente no topo da atmosfera (RK,K), foram aquelas que resultaram nos melhores índices estatísticos comparativamente à equação original de Brunt-Penman. Nessas equações foram impostas as condições de contorno: 0,3 ≥ RK,R ≥ 1 or RK,K ≤ 0,22. Embora com índices estatísticos semelhantes, uma análise de sensibilidade mostrou que a equação de Brutsaert e demais ponderadoras da nebulosidade resultaram em maiores desvios quando comparadas com a Equação original de Brunt-Penman, além de apresentarem complexidade superior para a aplicação prática.

New coefficients were determined for the weighting term for cloudiness in the Brunt-Penman equation using the rate of solar radiation (RK) in place of the rate of sunshine duration (n/N). The coefficients in the Brutsaert method proposed for daytime in southern Brazil were also tested and adjusted, and the method was selected which gave the more accurate daily results in relation to the original Brunt-Penman equation, for Santa Maria in the state of Rio Grande do Sul, Brazil (RS). Meteorological data covering 2,472 days obtained from the automatic and conventional weather stations in Santa Maria were used. The coefficients were adjusted by linear and nonlinear regression methods depending on the model, using 2/3 of the data. The adjusted equations were tested with the remaining 1/3 of the data. The Brunt-Penman equation modified by the term for cloudiness weighted both for solar radiation incident on the surface with no cloudiness (RK,R) and for solar radiation incident at the top of the atmosphere (RK,K), were those that resulted in the best statistical indices relative to the original Brunt-Penman equation. In those equations the boundary conditions, 0.3 ≥ RK,R ≥ 1 or RK,K ≤ 0.22, were imposed. Although having similar statistical indices, a sensitivity analysis showed that the Brutsaert equation and other weightings for cloudiness resulted in larger deviations when compared to the original Brunt-Penman equation, in addition to having greater complexity for practical application.

Este trabalho explora diferentes modelos não destrutivos de estimativa da área foliar de Solanum melongela L. através de medidas do comprimento (C) e largura (L) do limbo foliar. Para tanto, um cultivo de berinjela em estufa plástica foi conduzido no período de março a junho de 2007. Amostraram-se folhas de plantas em momentos aleatórios totalizando 186 folhas, sendo 98 utilizadas na estimativa dos parâmetros dos modelos e 88 para sua validação. As amostragens abrangeram amplo espectro de dimensões foliares, visando minimizar a raiz do quadrado médio do erro (RQME). Elas foram realizadas aos 71, 79, 81, 85, 92 e 99 dias após o transplante. Posteriormente obteve-se o maior número possível de discos foliares com o auxílio de um calador de 25 mm de diâmetro. Correlações foram realizadas entre a área foliar obtida pelo método dos discos com as dimensões lineares de L e C, o produto entre elas (CL) e o quadrado do comprimento multiplicado pela largura (C²L). Análises de regressão para 20 modelos foram obtidas, entre quadráticos, exponenciais, lineares, logarítmicos e de potência, dos quais 12 apresentaram coeficiente de determinação (R²) elevado. O modelo quadrático (Y = -5,78+0,4981CL-3,263.10-4CL²) e o da potência (Y = 0,4395CL1,0055) apresentaram melhores estimativas, com R² de 0,964 para ambos e RQME de 33,2 e 34,4, respectivamente. Com a medida apenas de uma dimensão foliar, o modelo quadrático (Y = -63,5+10,492L+0,2822L²; R² = 0,937; RQME = 44,1) apresenta-se como alternativa, pouco afetando a precisão da estimativa.

This paper explores different models of non-destructive leaf area estimates for Solanum melongela L. by the measure of leaf length (C) and blade width (L). The methodology involved eggplant cultivation in the greenhouse from March to June. Plant leaves were sampled at random throughout the growing season, totalizing 186 leaves, of which 98 were used to estimate the model parameters and 88 were used for model validation. The samples covered wide spectrum of leaf dimensions, in order to minimize root mean square error (RMSE). Leaves were sampled at 71, 79, 81, 85, 92 and 99 days after transplanting. The highest possible numbers of leaf discs were obtained with a 25 mm auger. Correlations were computed between the leaf area obtained by the discs method and the linear dimensions of L and C, the product of both (CL) and the square length multiplied by the width (C²L). Regression analyses for 20 models were tested, including quadratic, exponential, linear, logarithmic and power model, of which 12 had a high coefficient of determination (R²) value. The quadratic model (Y = - 5.78+0.4981CL- 3.263.10-4CL²) and the power model (Y = 0.4395CL1.0055) showed the best estimates, with R² of 0.964 for both, and RMSE of 33.2 and 34.4, respectively. With only one leaf dimension the quadratic model (Y = -63.5+10.492L+0.2822L²; R² = 0.937; RMSE = 44.1) is an alternative, with little impact on the precision.

Potato (Solanum tuberosum ssp. Tuberosum) crop is particularly susceptible to water deficit because of its small and shallow root system. The fraction of transpirable soil water (FTSW) approach has been widely used in the evaluation of plant responses to water deficit in different crops. The FTSW 34 threshold (when stomatal closure starts) is a trait of particular interest because it is an indicator of tolerance to water deficit. The FTSW threshold for decline in transpiration and leaf growth was evaluated in a drying soil to identify potato clones tolerant to water deficit. Two greenhouse experiments were carried out in pots, with three advanced clones and the cultivar Asterix. The FTSW, transpiration and leaf growth were measured on a daily basis, during the period of soil drying. FTSW was an efficient method to separate potato clones with regard to their response to water deficit. The advancedclones SMINIA 02106-11 and SMINIA 00017-6 are more tolerant to soil water deficit than the cultivar Asterix, and the clone SMINIA 793101-3 is more tolerant only under high solar radiation.

O objetivo deste trabalho foi estimar a duração dos subperíodos fenológicos e do ciclo de desenvolvimento da soja, de acordo com grupos de maturidade e datas de semeadura, e determinar as funções de distribuição de probabilidades que melhor caracterizam a distribuição destes dados. Foram avaliadas as funções exponencial, gama, lognormal, normal e Weibull, tendo-se verificado a de melhor ajuste aos dados de desenvolvimento simulado da cultura, de acordo com dados meteorológicos diários coletados de outubro de 1968 a julho de 2012, na estação climatológica principal de Santa Maria, RS. A simulação do desenvolvimento da cultura foi feita para diferentes datas de semeadura, com os grupos de maturidade (GM): 5.9-6.8, ciclo precoce/semiprecoce; 6.9-7.3, ciclo médio; e 7.4-8.0, ciclo semitardio/tardio. A função lognormal é a que melhor se ajusta à duração dos subperíodos e do ciclo da soja. Esta duração varia conforme a data de semeadura, com ciclo maior nas semeaduras antecipadas (outubro) e menor nas tardias (dezembro).

The objective of this work was to estimate the average length of phenological subperiods and of soybean development cycle as affected by maturity groups and sowing dates, and to determine the probability distribution functions that best characterize the distribution of this data. It was evaluated the exponential, gamma, lognormal, normal, and Weibull functions, and determined the one with the best fit to the simulated crop development data, using meteorological data collected from October 1968 to July 2012, at the main climatological station of Santa Maria, RS, Brazil. Crop development was simulated for different sowing dates, considering the maturity groups (GM): 5.9-6.8, early/semiearly cycle; 6.9-7.3, medium cycle; and 7.4-8.0, semilate/late cycle. The lognormal function has the best fit for the length of soybean subperiods and cycle. This length varies according to the sowing date, with bigger cycles in early sowings (October), and smaller ones at late sowings (December).

O objetivo deste trabalho foi elaborar uma escala diagramática para a avaliação visual e quantificação do dano causado por granizo em folhas de girassol. O trabalho foi conduzido em área experimental em Santa Maria (RS) no ano agrícola 2008/2009, sendo o dano causado por um evento de granizo ocorrido na data de 08/01/2009, com as plantas de girassol no estádio de plena floração (R5.1) e com índice de área foliar medido de 2,2 m² m-2. Foram coletadas 243 folhas danificadas que antes da coleta tiveram seu perímetro redesenhado com o auxílio de folhas inteiras de formato similar. Após a determinação da porcentagem de área danificada, foram selecionadas imagens para compor a escala diagramática logarítmica. O teste da escala foi realizado por 10 diferentes observadores em 24 folhas sorteadas dentre as 243 coletadas. A acurácia e a precisão de cada avaliador foram determinadas por regressão linear simples entre o dano real e o estimado com o auxílio da escala diagramática, além destes, utilizou-se a Raiz do Quadrado Médio do Erro (RQME), o erro absoluto e o coeficiente de determinação (R²) da regressão linear. Verificou-se que a escala é adequada para observação de dano foliar por granizo.

The objective of this study was to develop a diagrammatic scale for the visual assessment and the quantification of hail damage in sunflower leaves. The study was carried out in an experimental area in Santa Maria (RS) during the agricultural year of 2008/2009, the damage being caused by a hail-storm event which occurred on 8 January, 2009, with the sunflower plants in full bloom (R5.1) and a leaf-area index of 2.2 m²m-2. A total of 243 damaged leaves were collected, which before collection had their outlines redrawn with the aid of complete leaves of similar shape. After determining the percentage of the damaged area, images were selected to make up the diagrammatic logarithmic scale. A test of the scale was undertaken by 10 different observers on 24 randomly selected leaves from the 243 collected. The accuracy and precision of each appraiser were determined by simple linear regression of actual damage and that estimated with the aid of the diagrammatic scale, in addition we used the Root Mean Square Error (RMSE), the absolute error and the coefficient of determination (R²) of the linear regression. It was found that the scale is suitable for the observation of leaf damage caused by hail.

Foram determinados os coeficientes a e b da equação de Angströn-Prescott para a estimativa da radiação solar global para Santa Maria, RS. Utilizaram-se os dados diários da intensidade de fluxo de radiação solar global e de insolação (brilho solar) registrados na Estação Meteorológica pertencente ao 8° Distrito de Meteorologia, localizada no Campus da Universidade Federal de Santa Maria - UFSM, período 2002-2008. Os dados foram copiados no banco de dados do 8° Distrito de Meteorologia - 8° DISME, em Porto Alegre, e calculados os valores diários de radiação solar global no topo da atmosfera e de insolação máxima possível, considerando a latitude local. Com esses dados, foram determinadas as equações mensais e estacionais de regressão para a estimativa da radiação solar global em função da insolação. Constatou-se que existe alta correlação entre os dados de radiação solar global com aqueles de insolação, sendo, assim, possível estimar a radiação solar global em função da insolação.

Coefficients a and b of the Angströn - Prescott equation to estimate global solar radiation for Santa Maria, RS were determined. Daily data of global solar radiation and sunshine, were obtained from the Meteorological Station which belongs to the 8th District of Meteorology, located on the campus of the Federal University of Santa Maria - UFSM, period from 2002 to 2008. The mentioned data were copied from the database of the 8th District of Meteorology - 8th DISME in Porto Alegre. Top of atmosphere radiation and possible maximum sunshine were calculated considering local latitude. With such elements, monthly regression equations were determined for the estimation of solar radiation as a function of insolation. We found a high correlation between insolation and global solar radiation and it's possible to estimate the solar radiation depending on the measured insolation.

The objective was to study the leaf temperature (LT) and leaf diffusive vapor conductance (gs) responses to temperature, humidity and incident flux density of photosynthetically active photons (PPFD) of tomato plants grown without water restriction in a plastic greenhouse in Santa Maria, RS, Brazil. The plants were grown in substrate and irrigated daily. The gs was measured using a steady-state null-balance porometer on the abaxial face of the leaves during the daytime. Both leaf surfaces were measured in one day. The PPFD and LT were measured using the porometer. Leaf temperature was determined using an infrared thermometer, and air temperature and humidity were measured using a thermohygrograph. The leaves on the upper layer of the plants had higher gs than the lower layer. The relationship between the gs and PPFD was different for the two layers in the plants. A consistent relationship between the gs and atmospheric water demand was observed only in the lower layer. The LT tended to be lower than the air temperature. The mean value for the gs was 2.88 times higher on the abaxial than adaxial leaf surface.