Cardinal temperatures for the leaf development of Corymbia citriodora and Eucalyptus urophylla seedlings

Abstract

-The objective of this work was to estimate cardinal temperatures and phyllochron for the leaf development of the eucalyptus species Corymbia citriodora and Eucalyptus urophylla, in the seedling phase. A field experiment was carried out in a completely randomized design, in a 2x11 factorial arrangement, with the two eucalyptus species, 11 sowing dates, and five replicates, in the municipality of Itajubá, in the state of Minas Gerais, Brazil. The cardinal temperatures -base, optimum, and maximum -for leaf development were, respectively, 8.7, 17.1, and 41.3°C, for C. citriodora, and 11.5, 17.1, and 40.5°C for E. urophylla. The phyllochron of C. citriodora was 62.95°C day per leaf, and that of E. urophylla was 46.03°C day per leaf, which indicates that E. urophylla requires less energy accumulation than C. citriodora for leaf emission in the main stem.Index terms: air temperature, leaf emission rate, phyllochron, seedling quality, thermal requirement. Temperaturas cardinais para o desenvolvimento foliar de mudas de Corymbia citriodora e Eucalyptus urophyllaResumo -O objetivo deste trabalho foi estimar as temperaturas cardinais e o filocrono para o desenvolvimento foliar das espécies de eucalipto Corymbia citriodora e Eucalyptus urophylla, durante a fase de muda. Um experimento de campo foi realizado em delineamento inteiramente casualizado, em arranjo fatorial 2x11, com as duas espécies de eucalipto, 11 épocas de semeadura e cinco repetições, em Itajubá, MG. As temperaturas cardinais -basal inferior, ótima e basal superior -para o desenvolvimento foliar foram, respectivamente, 8,7, 17,1 e 41,3°C, para C. citriodora, e 11,5, 17,1 e 40,5°C, para E. urophylla. O filocrono de C. citriodora foi de 62,95°C dia por folha, e o de E. urophylla, de 46,03°C dia por folha, o que é indício de que E. urophylla necessita de menor acúmulo energético do que C. citriodora para a emissão de folhas na haste principal.Termos para indexação: temperatura do ar, taxa de emissão foliar, filocrono, qualidade de mudas, necessidade térmica.

Cardinal temperatures and thermal requirements for the initial development of two Brazilian native species

“…The optimum temperature was estimated (Lisboa et al, 2012;Freitas et al, 2017) by determining the thermal requirements for each species, sowing dates (12), and experimental units. Thermal requirements were obtained by the inverse of the angular coefficient (a) of the simple linear regression between the number of leaves (NL) in the main stem and the accumulated degree-days (DD) counting from the date when leaves first emerged (Table 1) .…”

“…agropec. bras., Brasília, v.54, e00525, 2019 DOI: 10.1590/S1678-3921.pab2019.v54.00525 Freitas et al, 2017), influencing the leaf appearance and the permanence period of trees in greenhouses and nurseries .…”

“…The effect of temperature, expressed in degree-days, is determined by the thermal time from which the daily cumulative thermal availability for the species can be computed within certain limits, called the cardinal temperatures (Muttoni et al, 2017). The cardinal temperatures are defined as follows: base temperature, which is considered the temperature below which metabolic processes are reduced, and development is null or diminished; optimum temperature, which is considered the temperature in which the maximum development occurs; maximum temperature, is that above which respiration is greater than photosynthesis, and development is null or diminished (Lisboa et al, 2012;Monteiro et al, 2014;Freitas et al, 2017).…”

“…Besides, plants are subjected to different air temperature conditions, as they can be planted in the different sowing dates or in the same sowing date, but in sites with distinct air temperature conditions (Luz et al, 2012;Souza & Martins, 2014). In some climatic conditions, such as subtropical climate, the convention is to use controlled temperature environments (Muttoni et al, 2017); however, this process is onerous and difficult to put into practice with forest species (Freitas et al, 2017).…”

“…Studies on cardinal temperatures are frequently carried out for annual and biannual cultures due to agricultural interest (Lucas et al, 2012;Luz et al, 2012;Gonçalves et al, 2015;Muttoni et al, 2017;Schmidt et al, 2018), but are practically nonexistent for perennial cultures (Souza & Martins, 2014;Freitas et al, 2017), mainly for tree species native to Brazil. Information on the capacity of a species to adapt to a wide range of environments is of great interest to producers and researchers, since knowledge of cardinal temperatures and thermal requirements values are important for developing and refining optimization strategies to manage and improve both production and its quality, as well as to integrate species that are more adapted to the climactic conditions of cultivation Freitas et al, 2017;Schmidt et al, 2018). Furthermore, this information constitutes important input data for forest management models applied to native forest trees, like gap models and mechanistic ones.…”