Towards the Reliable Prediction of Time to Flowering in Six Annual Crops. I. The Development of Simple Models for Fluctuating Field Environments

Abstract

Despite numerous altempts, the development of generalized models capable of accurate predictions of the times from sowing to flowering (f) of crop plants in field environments has remained elusive. Models which seek to corrclatcy\vith various states of environmental factors such as photoperiod, P, and temperature, T, using formal statistical procedures arc often complex. Here, we describe a family of photothermal responses (involving unambiguous parameters and limits) which quantify the linear, non-interacting effects of P and Tnot on^but on \/f, i.e. on the rate of progress towards (lowering. Based on these relations we suggest that the modelling of crop phenology will be simplified, more reliable and more biologically plausible. R. J. Summerficld el a/.: Prediction del tiempo defloration. RESUMENA pesar dc los numcrosos intcntos, aun cs imposiblc dcsarrollar modclos gcneralizados capaccs de predceir con exactitud los pcrfodos cntrc la sicmbra y la fioracion dc la plantas dc cultivo en ambicntes dc campo. Los modclos quc procuran corrclacionar la fioracion a los divcrsos cstados de los factorcs del medio ambicnte, tal como el fotopen'odo y la tempcratura, utili/.ando proccdimicntos cstadi'sticos formalcs, a menudo resultan muy complejos. En cstc articulo sc describe una familia dc rcspucslas fototcrmicas (quc implican paramctros y limitcs no ambiguos) quc cuantifican los cfectos lineales no intcractivos del fotopen'odo y la tempcratura, no en la fioracion sino en una lloracion, o sea, la velocidad del avancc hacia la fioracion. En base a estas rclaciones, sc sugicrc quc el modclado de la fenologfa de los cullivos podn'a scr simplificado, mas confiablc y mas plausible desde el punto de vista biologico.

Plant adaptation to temperature and photoperiod

“…Plant species are commonly classified into categories of long day, short day and day neutral plants. Daylength responses, however, also vary within species.Summerfield and his colleagues have carried out detailed studies on regulation of flowering in several crop species and conclude that the time when a crop flowers is determined almost exclusively by the genetically controlled responses to daylength and temperature (Summerfield et al 1991, Roberts et al 1993). On the basis of experiments under controlled conditions in which temperature and photoperiod could be independently manipulated, they have developed quantitative models that are reliable enough to predict when particular genotypes will flower in any environment.…”

Photoperiod affects the flowering time of field-sown balansa clover

“…Previous relationships between plant flowering and day length, that utilize long and short day plant classifications (Major, 1980) or photothermal time (Summerfield et al 1991), were unable to capture the variation in time of flowering as well as the straight thermal time model. The relationship was strongest for each cultivar when the model assumed the amount of time required from emergence to flowering was based on the duration and direction of photoperiod at emergence.…”

“…The effects of photoperiod on the time of flowering have been quantified using photothermal time as defined by Weir et al (1984). This method has been used to predict flowering time in many crops (Summerfield et al, 1991) including wheat (Porter et al, 1987) and subterranean clover (Evans et al, 1992). In most cases analyses have been based on the mean photoperiod experienced by the plant from emergence to flowering.…”

“…where FP is a photoperiod modification factor, Pp is the photoperiod at emergence in hours, Pp opt is the optimum photoperiod and the Pp base is the base photoperiod (Summerfield et al, 1991). Photoperiod was defined from sunrise to sun set, including civil twilight (Evans et al, 1992).…”

Heat stress impacts on wheat growth and yield were reduced in the Huang-Huai-Hai Plain of China in the past three decades

“…Previous controlled-environment experiments and crop modeling studies show that crop duration shortens with increase in mean temperature if adaptation options such as changes of sowing dates and cultivars are not taken into account (Summerfield et al, 1991). A shorter crop growth duration reduces the amount of radiation that is intercepted by the leaf canopy, and hence the biomass and grain yields decline.…”