Hamilton Telles Rosa

Filocrono de genótipos de arroz irrigado em função de época de semeadura

The phyllochron is defined as the time needed for appearance of successive leaves on a culm in plants of the Poaceae family. Using the concept of phyllochron, it is possible to calculate the number of accumulated leaves, which is an excellent parameter to measure the plant development. The objective of this study was to estimate the phyllochron of seven rice cultivars grown in Southern Brazil in five sowing dates in the Central Region of Rio Grande do Sul State. A two-year field experiment was carried out in Santa Maria, RS, Brazil during 2003/2004 and 2004/2005 growing seasons, with five sowing dates each year. Seven rice cultivars recommended for Southern Brazil were used: IRGA 421, IRGA 416, IRGA 417, IRGA 420, BR-IRGA 409, BRS 7 TAIM and EPAGRI 109. The phyllochron (°C day leaf-1) was estimated by the inverse of the slope of the linear regression between main culm number of accumulated leaves (represented by the Haun Stage) and thermal time (base temperature = 11°C) accumulated from plant emergence. Genotype differences are small and can be neglected, but the environment, mainly through sowing date, has a large effect on phyllochron in rice.

Crescimento vegetativo e produtivo de duas cultivares de morango sob épocas de plantio em ambiente subtropical

The proper growth of leaves results in an increase in leaf area, which allows for greater interception of solar radiation, and consequently greater photosynthetic activity and better crop productivity for different planting times. The objectives of this work were to obtain equations in order to estimate leaf area from the linear dimensions of the leaf blades, to establish allometric relationships between the leaf area and the number of leaves in the primary crown, and to determine the productivity of fruits for different planting dates of two strawberry cultivars. The experiment was carried out at the experimental area of the Department of Plant Science, at the Federal University of Santa Maria, in Santa Maria, Rio Grande do Sul, with the Araza and Yvapita cultivars. Plants were sown on six dates: 03/04/2008, 07/05/2008, 02/06/2008, 02/02/2009, 02/04/2009 and 02/06/2009. The experimental design used was of randomised blocks with four replications (plots of 30 plants each). In each plot, six plants were tagged for weekly determination of the number and area of leaves in the primary crown, and the fresh weight and number of fruits per plant. The power model satisfactorily characterised the allometric relationship between the development of the leaf area and the number of leaves accumulated in the primary crown. Fruit production was influenced by planting time, so that early planting in the period recommended by EMBRAPA (April) provides greater leaf area at the beginning of flowering, and a higher yield potential, especially in years with high solar radiation in the spring, as happened in 2008.

Simulação do rendimento de grãos de arroz irrigado em cenários de mudanças climáticas

The objective of this work was to simulate rice grain yield in climate change scenarios with increasing of current atmospheric CO2 concentration and increases in mean air temperature in Santa Maria, RS, as well as to verify possible implications on current recommendations of sowing period. Climate change scenarios for the next one hundred years considering doubled CO2 concentration and increases of 1, 2, 3, 4 and 5°C were used. Rice grain yield was simulated with the InfoCrop model. Simulations were performed considering three rice cultivars - IRGA 421, IRGA 417 and EPAGRI 109 - and seven sowing dates spaced monthly from July 20 th to January 20 th . An increase in rice grain yield was observed in the climate change scenarios simulated for the three cultivars, with higher increase for the very early cultivar (IRGA 421) and lower increase for the late cultivar (EPAGRI 109). If climate change takes place, currently sowing period recommended for irrigated rice shall be enlarged.

Base temperature for leaf appearance and phyllochron of selected strawberry cultivars in a subtropical environment

Leaf development is characterized by the appearance of new leaves and is related to crop leaf area index, which affects the interception of solar radiation used for photosynthesis and biomass production and ultimately defines crop yield. The objectives of this paper were to estimate the base temperature for leaf appearance and to determine the phyllochron of two strawberry cultivars considering several planting dates. A two-year field experiment was conducted during 2008 and 2009 in Santa Maria (RS). The cultivars Araza (early) and Yvapita (late) were used at three planting dates in both years. Base tempera- ture (Tb) was estimated using the Mean Square Error (MSE) approach of the regression between accumulated leaf number (LN) and accumulated thermal time (ATT). The phyllochron was calculated as the inverse of the slope of the regression of LN against ATT. Estimated Tb for leaf appearance in both cultivars was 0 °C. Variations in phyllochron were observed among the two cultivars, among planting dates and also during the plant developmental period of each cultivar. Before flowering, the phyllochron was similar in both cultivars and after flowering it was higher in cultivar Araza. Phyllochron was greater for later planting dates and increased at short photoperiods in Fall and Winter. Results showed that both cultivars have a typical long- day plant response because phyllochron decreased as photoperiod increased up to approximately 11.8 hours, and phyllochron was the lowest at longer photoperiod.

Adaptação e avaliação do modelo infocrop para simulação do rendimento de grãos da cultura do arroz irrigado

This study aimed to adapt and evaluate the InfoCrop model for simulating grain yield of irrigated rice in Santa Maria, state of Rio Grande do Sul, Brazil. The grain yield of irrigated rice was simulated considering three versions of the InfoCrop model with adaptations for local rice cultivars. Simulated yields were compared to the yields observed in the Santa Maria county surveyed by the Instituto Riograndense do Arroz (Institute of Rice of Rio Grande do Sul - IRGA) from 1996/97 to 2008/09, and to the yields of experiments conducted at the Universidade Federal de Santa Maria (Federal University of Santa Maria - UFSM) from 1998/1999 to 2005/2006. The InfoCrop model captured the interannual variability of the grain yield of irrigated rice for the Santa Maria county and the experiments conducted at UFSM. The root mean squared error of the simulation of grain yield using the Version 3 of the InfoCrop model (better performance), considering all data observed, was 0.850 Mg ha-1, with overestimation trend, which may have occurred because the model considers a situation of potential yield, which does not always occur in commercial farming.

O fenômeno El Niño Oscilação Sul e a variabilidade interanual da evaporação do tanque Classe A e da umidade relativa do ar em Santa Maria, RS

The objective of this study was to associate the interannual variability of Pan evaporation and air relative humidity with the El Nino Southern Oscilation (ENSO) phenomenon in Santa Maria, RS, Brazil. Daily data records of Pan evaporation (PAN, mm day-1) and mean daily relative humidity (RH, %) measured in Santa Maria, RS, were used. PAN was measured from 1973 to 2006 and RH was measured from 1969 to 2006. Years were grouped into El Nino (EN) years, La Nina (LN) years, and Neutral (N) years, from July 1st of the year to June 30th of the following year. Results showed that PAN is lower in EN years and greater in LN years. On the other hand, RH was greater in EN years and lower in LN years. The effect of ENSO on PAN is greater in November, December, January, and May, whereas RH is affected by ENSO in October, November, December and May.

Soma térmica de algumas fases do ciclo de desenvolvimentoda escala de counce para cultivares sul-brasileirasde arroz irrigado

The COUNCE scale is a developmental scale recently proposed for rice and that is being used in Brazil. However, the duration of developmental phases of this scale in degree-days is not available for Brazilian irrigated rice cultivars. Thus, the objective of this study was to determine the thermal time of some developmental phases of the COUNCE scale in irrigated rice cultivars grown in Southern Brazil using different calculation methods and cardinal temperatures throughout the crop cycle. A field experiment was carried out in Santa Maria, RS, Brazil, during two years (2003/2004 and 2004/2005), with five sowing dates in each growing season. The experimental design was completely randomized with four replications. Each replication was a 12-liter pot with 10 plants. The cultivars used were IRGA 421, IRGA 416, IRGA 417, IRGA 420, BR-IRGA 409, BRS 7 TAIM, and EPAGRI 109. The date of R2 (colar of the flag leaf visible) and R9 (all grains with brown hulls) stages of the COUNCE scale were recorded on the main culm of five tagged plants per pot. Using the cardinal temperatures of 11 °C, 28 °C, and 40 °C, the thermal time of the emergence-R2 phase was 700-800 °C day for the very early cultivar, 1000-1400 °C day for early cultivars and 1300-1700 °C day for intermediate and late cultivars, and the thermal time of the R2-R9 phase was 400-700 °C day with no relationship with the developmental cycle of the cultivar.

Mudança climática e seus efeitos na cultura do arroz

Since the industrial revolution there was an increase in the atmospheric greenhouse gases, such as the carbon dioxide (CO2), which may lead to an increase in global temperature by the end of the 21th century. The direct effect of the increase in the CO2 concentration on plants is the possibility of increasing plant growth rate and crop yield, once CO2 is the substrate for photosynthesis. If the increase in CO2 concentration will be accompanied by an increase in air temperature, there may not be an increase in plant growth and crop yield because of a shortening of the developmental cycle an increase in plant tissue respiration. However, the response to elevated CO2 and temperature varies depends upon the crop. Thus, the objective of this review is to assemble information about the ecophysiological response of rice crop, one of the tree major cereals produced and consumed by the world population, to climate change. Plants with the C3 metabolism, as rice, are more benefitted from the increase in atmospheric CO2 concentration than plants with the C4 metabolism. High daytime and nighttime temperatures may drastically reduce the yield potential of rice crop due to shortening of the developmental cycle and spikelet sterility. Such a trend can be mitigated by selecting genotypes more resistant to conditions of high air temperature during flowering and by changing the sowing date.

Desenvolvimento vegetativo e reprodutivo de cultivares de trigo e sua associação com a emissão de folhas

The objective of this study was to determine the relationship between the duration of vegetative, reproductive and total developmental cycle with the main stem final leaf number and with the main stem leaf appearance rate in Brazilian wheat cultivars, varying the sowing date. A field experiment was carried out in Santa Maria, RS, in 13 sowing dates during three years (2005, 2006 and 2007). Six wheat genotypes with developmental cycle varying from early to late were used: BRS LOURO, CEP 52, BRS 177, CEP 51, NOVA ERA, and BRS TARUMA. For each cultivar and sowing date, the duration, in °C day, of the vegetative (emergence - anthesis), reproductive (anthesis - physiological maturity) phases, and total developmental cycle (emergence - physiological maturity), the main stem final leaf number and the phyllochron (time interval between the appearance of two successive leaves) were determined. The relationship between these variables was tested through a regression analysis. The results indicate that the duration of total developmental cycle of wheat is directly related with the duration of the vegetative phase and not with the duration of the reproductive phase, which was similar among cultivars. The duration of the vegetative phase is related with main stem final leaf number and not with leaf appearance rate.

Desenvolvimento vegetativo em diferentes hastes da planta de mandioca em função da época de plantio

Studies on the vegetative development of cassava grown in subtropical conditions of Brazil are scarce. The objective of this study was to determine the phyllochron and the final leaf number on the main stem and on sympodial branches of a cassava variety grown in different planting dates in a subtropical climate. A field experiment was conducted in Santa Maria, RS, with four planting dates: 09/26/2006, 10/18/2006, 11/08/2006 and 11/28/2006. The variety FEPAGRO RS13, with tricotomic growth habit, was used in a complete randomized design with four treatments (planting dates) and four 4.0 x 9.0m plots with five rows and 0.8 x 0.8m spacing in each planting date. On the main stem (MS) and on the first order (BR1) and second order (BR2) sympodial branches of six plants per plot randomly selected, the number of visible leaves (NL) on a weekly basis, and the final leaf number (FLN) were measured. The phyllochron on MS, BR1 and BR2 was estimated by the inverse of the slope of the linear regression of NL against accumulated thermal time, assuming a base temperature of 14°C. Phyllochron increased in the sequence MS BR1>BR2. Both phyllochron and FLN varied according to planting date, with photoperiod being a possible cause of such variation. Within BR1 and BR2 sympodial branches, phyllochron and FLN were not different among stems.