The objective of this work was to estimate the cardinal temperatures and to quantify the thermal requirements for the initial development of seedlings of the native tree species Citharexylum myrianthum and Bixa orellana. A field experiment was carried out in a completely randomized design, in a 2?12 factorial arrangement (2 tree species and 12 sowing dates), with five replicates. The base, optimum, and maximum temperatures for the development of C. myrianthum were 11.4, 18.1, and 36.6°C, and, for B. orellana, 12.0, 18.4, and 46.4°C. The thermal requirements for the development of C. myrianthum was 66.7°C day per leaf, and, for B. orellana, 82.5°C day per leaf. In the initial development, B. orellana shows a large thermal amplitude and is tolerant to extreme temperatures, while C. myrianthum shows a large thermal amplitude, but a lower thermal requirement and a more rapid development than B. orellana.

The aim of this study was to estimate cardinal temperatures (base, optimum, and maximum), and simulate the vegetative development of guava crop through phyllochron (linear) and Wang and Engel (nonlinear) models at the seedling phase. The experiment was conducted in Itajubá, MG, Brazil (22° 24’ 46.43” S 45° 26’ 48.94” W), for two years in a completely randomized design with twelve sowing dates and five experimental units per treatment, totaling sixty experimental units. The cardinal temperatures were estimated using twelve methods described in the literature and the values were: base, 10.9 °C, optimum, 17.3 °C and maximum, 51.2 °C. The phyllochron model was superior to Wang and Engel’s model for simulation of vegetative growth of guava, with root mean square error of 1.5 leaves.

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The aim of this study was to simulate the vegetative development of the olive cultivars Arbequina and MGS ASC315 cultivated in Maria da Fé, MG, Brazil (22° 18’ 29” S, 45° 22’ 31” W, 1.276 m of altitude). The development of these cultivars was simulated in nine transplanting dates, considering three distinct scenarios for three periods (2011-2040, 2041-2070 and 2071-2100). Climate changes influence the olive crop management. The increase in air temperature modifies the development rate and the duration of the seedling phase of the cultivars Arbequina and MGSASC315. In colder months, there is accelerated vegetative development and shorter seedling phase duration. Conversely, in warmer months, there is delayed development with longer seedling phase duration.

Air temperature and photoperiod play an important role in the seedling development for tropical forest species. Both variables are sensitive to climate, and so evaluating thermal and photoperiodic effects on seedling development is fundamental, especially for climate change studies. Methods to quantify thermal time and the energy required for plants to reach a development stage include air temperature and cardinal temperatures. The photoperiod will also affect physiological reactions of a plant and thus its development. Here we evaluated the six thermal time methods widely used to compute thermal requirement, and identified the influence of the photoperiod from the 2015 and 2016 growing seasons and 12 sowing dates in Itajubá, Minas Gerais state, Brazil, on seedling development of three native tropical forest species Psidium guajava L. (Myrtaceae), Citharexylum myrianthum Cham. (Verbenaceae), and Bixa orellana L. (Bixaceae). The method used to quantify thermal time influenced the analytical results of seedling development; the one that considered three cardinal temperatures and compared them with the mean air temperature (Method 5) performed better in computing thermal requirements. The influence of photoperiod on seedling development was inconclusive for the three species, but all three developed better in mild temperatures (between 13.3 °C and 26.9 °C) with a photoperiod shorter than 13 h.