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The role of phytotrons in
agricultural research
L. T. Evans
SUMMARY
he most important contribution of phytotrons to agricultural research lies in
the means they provide to clarify the objectives of plant breeding and agronomic
programs. particularly by unravelling the effects of covaryiiig and interacting
components of climate. Examples are drawn from analyses of the epidemiology
oi‘ blue mold disease in tobacco. and of the effects of radiation and temperature on
grain filling and yield determination in wheat. Pronounced interactions occur
between several climatic factors. but particularly between day length and night
temperature and their effects on the reproductive cycle.
Where particular climatic conditions impose a major bottleneck on crop
production, phytotron conditions can he used as a selection sieve for parents
and progeny in plant breeding programs. Ways of improvulg performance at both
ahovc- and below-optimal temperatures are considered.
Phytotrivns are powerful tools for the analysis of day length and temperature
requirements for reproduction in plants. and provide many opportunities for
the modification and acceleration of crop life cycles in plant breeding programs.
Problems of emrapolation from phytotron to field are considered, and several
examples are given of agreement between the two kinds of experiments. Finally.
a plea is made for more experiments with simulated plant communities and with
plants prestressed to give responses more relevant to those of tield-grown plants.
INTR()DUC TION
Experiments in the field must always play a crucial role in agricultural research,
at both the beginning and the end of the process. On the one hand, they identity
or highlight major problems for investigation". on the other, they provide thc
ultimate tcst of thc new genotypes or agronomic practices dcvclopcd as solu—
tions to those problems. Between identification and solution of the problems.
however. there is a period of reciprocating analysis and synthesis during vrhich
experiments in controlled environments can clarify’ tibjcctivcs. unravel the
effects of covarying and interacting components of the environment. manipulate
lifc cycles for plant brccding purposes, and provide more reproducible, specific,
and rapid selection of cultivars and practices to deal with the problem.
L. T. Evans. Division of Plant Industry. Commonwealth Scientific and Industrial Research (lrganization
[CSIRU). Canberra. Australia.