Effects of temperature and photoperiod onSetaria viridis

Abstract

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.

Effects of Temperature and Photoperiod on the Phenological Development of Barnyardgrass

“…This finding is in contrast to green foxtail, where sensitivity to photoperiod was apparent only up to initiation of heading and further phenological development was independent of photoperiod. The number of thermal days required to reach initiation of flowering, seed set, and end of seed set was similar across all photoperiods (Swanton et al, 1999) Our results for barnyardgrass, however, agree with the findings of Vengris et al (1966) They reported that plants under a LD (16 h) condition headed and produced mature seeds much later than similar plants under SD (11 h) conditions. In an 11‐h photoperiod, barnyardgrass headed about 35 DAE and produced mature seeds at about 52 DAE, whereas under a 16‐h photoperiod, heading occurred at about 53 DAE and produced mature seeds at 90 DAE.…”

“…For example, Muldoon et al (1982) reported that the relative growth rate and accumulation of shoot dry weight of Japanese barnyard millet ( Echinochloa utilis Ohwi et Yabuno) and paisa ( E. frumentacea L.) were positively correlated with an increase in temperature from 15/10 to 33/28°C. Rate of leaf appearance in velvetleaf ( Abutilon theophrasti L.) also increased with temperature from 12/4 to 26/18°C and declined at higher temperatures (Patterson, 1992) Similarly, Swanton et al (1999) reported that the rate of leaf and tiller appearance and shoot elongation of green foxtail increased with temperature up to 35/25°C and declined at higher temperatures.…”

“…Phenological models have been developed with a considerable degree of success for wheat, corn, sorghum [ Sorghum bicolor (L.) Moench. ], rice, cotton (Hodges, 1991b), and green foxtail (Swanton et al, 1999)…”

“…At this photoperiod a total of 25.2 thermal days was required for barnyardgrass to complete its life cycle. Swanton et al (1999) reported that green foxtail required a total of 19.6 thermal days at this photoperiod to complete its life cycle. Plants exposed to the 16‐h photoperiod took longer to reach the same phenological stages.…”

“…Therefore, to provide biological information for modeling purposes, the objectives of this research were to characterize the phenological development of barnyardgrass in response to variations in temperature and photoperiod by determining the duration of the juvenile phase and the effects of temperature and photoperiod on reproductive development. A similar approach was taken by Swanton et al (1999) to characterize the phenological development of green foxtail ( Setaria viridis L.).…”