Growth and Development of Purple Nutsedge Based on Days or Thermal Units

Abstract

-This work was carried out with the objective of elaborating mathematical models to predict growth and development of purple nutsedge (Cyperus rotundus) based on days or accumulated thermal units (growing degree days). Thus, two independent trials were developed, the first with a decreasing photoperiod (March to July) and the second with an increasing photoperiod (August to November). In each trial, ten assessments of plant growth and development were performed, quantifying total dry matter and the species phenology. After that, phenology was fit to first degree equations, considering individual trials or their grouping. In the same way, the total dry matter was fit to logistic-type models. In all regressions four temporal scales possibilities were assessed for the x axis: accumulated days or growing degree days (GDD) with base temperatures ( ).Keywords: Cyperus rotundus, growing degree days, phenology, base temperature, modeling. y = 37,678/(1+(x/509,353) -7,047 ). RESUMO -Este trabalho foi desenvolvido com o objetivo de elaborar modelos matemáticos para previsão do crescimento e desenvolvimento da tiririca (Cyperus rotundus) com base em dias ou unidades térmicas acumuladas (graus-dia). Para isso, dois experimentos independentes foram desenvolvidos: o primeiro com fotoperíodo decrescente (março a julho) e o segundo com fotoperíodo crescente (agosto a novembro). Em cada experimento, foram realizadas dez avaliações de crescimento

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

“…For other weed species, the Tb found was of: around 10°C for honeyweed (Leonurus sibiricus L.), by Silva et al (2014a); 12°C for southern sandbur (Cenchrus echinatus L.), by Machado et al (2014); 12ºC for purple nutsedge (Cyperus rotundus L.), by Lima et al (2015); and 10 or 15°C for sourgrass [Digitaria insularis (L.) Mez ex Ekman], by Marques et al (2014). In this context, in general, species with better adaptation to cold climate, with C3 photosynthetic cycle and smaller size, have Tb below 10°C.…”

“…Traditionally, days are adopted as the unit of time, but this variable is often subjected to environmental interference, which is also indirectly expressed on phenology (Machado et al, 2014;Marques et al, 2014). Therefore, when there is no water stress, temperature has been regarded as the most important weather factor to predict physiological events (Gadioli et al, 2000;Lima et al, 2015).…”

“…Moreover, there is a linear relationship between temperature increase and plant growth (Gadioli et al, 2000). Therefore, mathematical models and simulation routines based on the concept of accumulated GDD may be used (Machado et al, 2014;Lima et al, 2015). Even though this concept is not different for weeds, few studies have evaluated the development of these species based on GDD (Marques et al, 2014).…”

Crescimento e desenvolvimento, resistência múltipla aos herbicidas inibidores da EPSPS-ALS e alternativas em pós-emergência para controle de <i>Amaranthus palmeri</i> (S.) Wats

“…(2) Inicialmente, adotou-se técnica de análise por grupo de experimentos, comparando-se a variabilidade dos experimentos por meio do teste de Hartley (PEARSON;HARTLEY, 1956). Em seguida, as análises do desenvolvimento fenológico das plantas foram ajustadas ao modelo linear, conforme adotado por Lima et al (2015). As variáveis quantitativas, relacionadas com o crescimento das plantas, foram analisadas por meio de regressões nãolineares.…”

“…Para tanto, a utilização de análises de crescimento é um método acessível e preciso para inferir a contribuição de diferentes processos fisiológicos para o crescimento vegetal, possibilitando o conhecimento da cinética de produção de biomassa das plantas, sua distribuição e eficiência ao longo da ontogenia (AUMONDE et al, 2013;LIMA et al, 2015).…”