Growth and development of Conyza bonariensis based on days or thermal units

Abstract

-The objective of this work was to evaluate the growth and development of a glyphosateresistant population of Conyza bonariensis in different sowing dates (autumn, winter, and spring) and in two agricultural environments, based on days or thermal units. Five experiments were performed in two agricultural environments in Brazil: two in the municipality of Não-Me-Toque, in the state of Rio Grande do Sul -with sowings in July and September 2011; and three in the municipality of Santa Cruz das Palmeiras, in the state of São Paulo -with sowings in April, July, and September 2011. In each trial, ten evaluations of the phenological development and total dry mass of C. bonariensis were performed, fitting these variables to a unit of time in days or growing degree days. The phenological development of C. bonariensis had the best adjustment at the base temperature of 8.4o C, and was affected by sowing date and agricultural environment. In autumn, with decreasing temperature and photoperiod, plants are still able to accumulate dry mass, but without floral induction. In spring, with increasing temperature and photoperiod, dry mass accumulation is lower, but phenological development is faster, with significant floral induction.

Conyza bonariensis growth and development according to thermal time accumulation and photoperiod

“…Another study evaluating hairy fleabane, that was sown in spring under subtropical environment conditions, showed a floral induction faster than plants with a sowing date in winter and fall, in which the difference to reach the flowering stage between seasons was greater than 30 days (Soares et al, 2017), confirming the results of the present study (Table 2). This was attributed to the elevation of the average air temperature.…”

“…In which T avg is the mean air temperature (°C) calculated by the arithmetic mean of the minimum and maximum daily air temperatures; and T b is the base temperature (T b ) which was used at 8.4°C (Soares et al, 2017). The thermal time accumulation (TTa, °C day) was obtained through the sum from GDD:…”

“…Recent findings show that the sowing date influences the phenological development of hairy fleabane (Soares et al, 2017). Seed of this plant that emerged under decreasing temperature and photoperiod conditions show an increase of dry matter production and reduced flowering induction, whereas under increasing temperature and photoperiod conditions there is less accumulation of dry matter and more flowering induction (Soares et al, 2017). Therefore, based on the climatic conditions, it is possible to predict this species development and, then, make recommendations for control at the appropriate time.…”

“…Growth and development stages of weeds are best defined by environmental conditions (Marques et al, 2014). The stem elongation in a hairy fleabane plant begins around four weeks after emergence, in the subtropical environment (Kaspary et al, 2017), which can happen with changes according to temperature and photoperiod conditions (Soares et al, 2017). There is no information on the environmental factors that control this behavior, mainly those related to thermal time accumulation.…”

Thermal Requirement and Phenological Characterization of Papaya Varieties Cultivated Under Subtropical Climate

“…An efficient way of studying the phenological and productive behaviour of a crop is through temperature, relating it to the thermal sum expressed in degree-days, which has been used to estimate the amount of heat required for plants growth and development (SOARES et al, 2017). Currently, thermal sum has been widely used to correlate phenological phases of a single culture (CHIOU; HSIEH; CHIEN, 2015); therefore, the current study was performed by using such technique to quantify the time needed for any phenological phase in any kind of environmental conditions, regardless the species (LUCAS et al, 2012;RODRIGUES;LIMA, 2013;MATOS et al, 2014).…”