Josana Andreia Langner

Estimativa das temperaturas cardinais e modelagem do desenvolvimento vegetativo em batata-doce

The objective of this study was to determine the cardinal temperatures of sweet potato and to compare the simulation of node appearance with the plastochron model (linear) and with Wang and Engel model (nonlinear) and the best way to input air temperature in the models. Model calibration and test were conducted with data of number of nodes on the main stem of sweet potato, cultivar Princesa, collected in experiments carried out in Santa Maria, RS, Brazil, at seven planting dates in 2010, 2011 and 2012 growing seasons. Better model predictions were obtained using the cardinal temperatures of 12, 30 and 40 oC. The plastochron and Wang and Engel models showed similar performance. The version of the models that uses mean temperature as input was superior to the version with the minimum and maximum temperatures as input. Both models can be used to simulate the development of sweet potatoes when it is cultivated in the recommended period. Outside this period it is suggested to use the Wang e Engel model.

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.

Parâmetros quantitativos de hastes florais de gladíolo conforme a data de plantio em ambiente subtropical

The objective of this work was to determine the growing seasons, in a subtropical environment, when it is possible to produce gladiolus ( Gladiolus x grandiflorus ) stems that meet commercial, quantitative standards for cut flowers of the national market. Two field experiments were carried out – one from August 2011 to July 2012, and the other from August 2012 to July 2013 – with three gladiolus cultivars and 12 planting dates for each experiment. Stem total length, rachis length, and stem diameter were evaluated at the harvesting point, when the petal color appears in the first three florets at the stem base. The best months for production of gladiolus stems are July, August, September, February, March, and April, although in the other planting dates the stem quality was never below the minimum standard (except for the periods of frost during heading).

Limite crítico no solo para transpiração e crescimento foliar em mandioca em dois períodos com deficiência hídrica

A cassava crop is often exposed to more than one period of water deficit during the growing season. The objective of this study was to verify if there is a difference in the FTSW (fraction of transpirable soil water) threshold for transpiration and leaf growth in cassava plants subjected to one or two periods of water deficit. Two experiments with cassava (Fepagro RS 13 cultivar) were conducted. Treatments were four soil water regimes subdivided into two periods, period 1 (P1) and period 2 (P2): water regimes WR1 and WR2 (with water deficit in both periods and without water deficit in both periods, respectively), and water regimes WR3 and WR4 (with water deficit only in P1 or P2, respectively). The FTSW approach was used to indicate the threshold for transpiration and leaf growth. The FTSW threshold was 0.35, 0.38, and 0.37 for leaf growth and 0.28, 0.26, and 0.28 for transpiration in P1 of WR2 and WR3 and P2 of WR4, respectively. In P2 of WR2, the FTSW threshold for leaf growth and transpiration was 0.09 and 0.13, respectively. It was concluded that there is a decrease in the FTSW threshold in cassava during the second period compared to the first period of soil water deficit, which can be explained by the smaller leaf area, which allowed a longer leaf turgor period, thus delaying activation of the stomata control mechanisms. The practical implication of these results is that they can be used as parameters for crop irrigation, as well as for selecting cultivars more tolerant to water deficit.

Assessing the response of maize phenology under elevated temperature scenarios

The objective of this study was to simulate the development of maize in elevated temperature scenarios at Santa Maria, RS, Brazil. The developmental cycle of maize was simulated with the Wang and Engel (WE) model with genotype-dependent coefficients for the cultivar BRS Missoes. The developmental cycle was divided into vegetative phase (from emergence to silking), and reproductive phase (from silking to physiological maturity). Twelve sowing dates throughout the year were considered, resulting in emergences on the day 15 of each month all year round. Climate scenarios used were synthetic time series of 100 years of current climate and with increase in mean air temperature of +1, +2, +3, +4, and +5, with symmetric and asymmetric increases in daily minimum and maximum temperatures. As temperature increased, the number of years in which crop was killed by frost decreased, indicating that if global warming will confirm, the growing season for maize grown in subtropical environment will be longer by the end of this century. Maize vegetative and reproductive development was delayed or hastened depending upon the emergence time of the year, and if the increase in air temperature is symmetric or asymmetric, indicating complex Genotype x Environment interactions and high vulnerability of maize development to climate change.