repeatedly demonstrated that knowledge of phenological development is critical in understanding crop growth,
. 2000. Effects of photoperiod on the phenological development of redroot pigweed (Amaranthus refroflexus L.). Can. J. Plant Sci. 80: [929][930][931][932][933][934][935][936][937][938]. Mechanistic weed models focus on determining the outcome of weed and crop interference. An understanding of weed phenology is essential for simulation model development. Phenological development is a major factor determining the outcome of weed-crop competition. Growth cabinet studies were conducted to characterize the influence of photoperiod on the phenological development of redroot pigweed (Amaranthus retroflexus L.). Results indicated that redroot pigweed is a quantitative short-day species. Four development phases of redroot pigweed were described according to its response to photoperiod: (1) a juvenile phase of 1.1 d; (2) a photoperiod-sensitive inductive phase of 7.9 d; (3) a photoperiod-sensitive post-inductive phase of 39.9 d; and (4) a photoperiod-insensitive phase of 2.2 d. This information is useful for the development of mechanistic models and for comprehending the distribution and competitive ability of redroot pigweed with crops. The utilization of these results could help in predicting the phenological development of redroot pigweed.Key words: Phenology, mechanistic weed models, juvenile phase Huang, J. Z., Shrestha, A., Tollenaar, M., Deen, W., Rahimian, H. et Swanton, C. J. 2000. Effets de la photopériode sur la phénologie de l'amarante à racine rouge (Amaranthus retroflexus L.). Can. J. Plant Sci. 80: 929-938. Les modèles mécanistes des infestations de mauvaises herbes se concentrent sur la résultante de la compétitivité entre mauvaises herbes et cultures. La compréhension de la phénologie des mauvaises herbes est un préalable essentiel à la construction de modèles en simulation car le développement phénologique est un facteur de première importance pour l'issue de la compétition mauvaises herbes-cultures. Nous avons conduit des travaux en armoire de croissance pour caractériser l'influence de la photopériode sur la phénologie de l'amarante à racine rouge (Amaranthus retroflexus L.). L'amarante apparaît comme une espèce de jour court quantitative. Nous avons dégagé quatre phases de développement de l'amarante selon sa réaction à la longueur de la photopériode : 1) une phase juvénile de 1,1 j; 2) une phase d'induction florale sensible à la photopériode de 7,9 j; 3) une phase post-induction, sensible à la photopéri-ode de 39,9 j; 4) une phase photo-apériodique de 2,2 j. Ces renseignements sont utiles pour la construction de modèles mécanistes et pour comprendre le mode de répartition spatiale de la mauvaise herbe ainsi que sa compétitivité envers les cultures. Ils pourraient également faciliter la prédiction de son développement phénologique. Mots clés: Phénologie, mécaniste, modèles d'infestation de mauvaises herbes, phase juvénileIntegrated weed management (IWM) is a multidisciplinary approach that utilizes various methods of weed control within a cropping system Swanton and Murphy 1996). The success of IWM ca...
Understanding the environmental variables influencing the phenological development of weeds is essential for simulation model development. Temperature and photoperiod are important variables governing the phenological development of weeds. Growth cabinet studies were conducted to characterize the phenological development ofSetaria viridisin response to variations in temperature and photoperiod and to determine the duration of the juvenile phase and the effect of temperature and photoperiod on reproductive development.Setaria viridiswas adapted to a temperature range from 6.5 to 47 C. Phenological development ofS. viridiswas described accurately in terms of thermal days (cumulative day degrees above a base temperature) and biological days (Bd: chronological days at the optimum temperature and photoperiod). Four developmental phases ofS. viridiswere described: (1) a juvenile (photoperiod insensitive) phase of 2.6 Bd; (2) a photoperiod-sensitive inductive phase of 2.2 Bd; (3) a photoperiod-sensitive postinductive phase of 6.0 Bd; and (4) a photoperiod-insensitive inductive phase of 10.9 Bd. Photoperiod sensitivity ofS. viridisdid not differ with stage of development when expressed as a rate. Interpretation of constant sensitivity to photoperiod will simplify simulation of weed phenology in mechanistic models.
The effect of three spray variables (droplet number, active ingredient concentration, and droplet size) on uptake and translocation of formulated 14C-triclopyr ester was studied in greenhouse-grown Populus tremuloides seedlings. The dose per plant in all treatments was held constant. In all experiments, absorption (as a percentage of dose applied) was much greater than translocation (as percentage of dose absorbed). Absorption and translocation decreased as concentration (ai) was increased and droplet number decreased. Absorption and translocation also decreased as droplet number decreased and droplet size increased. When concentration (ai) was increased and droplet size decreased, absorption again decreased but to a much lesser extent than in the other two experiments; there was no significant effect on translocation. A time-course experiment indicated that uptake rate began to decrease within 1.5 h of application. The rate of decrease was greater at the higher concentration (ai), suggesting that the decrease was associated with contact injury. A model to integrate the application parameters and translocation gave a high correlation between dose per unit droplet stain circumference and translocation.
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