Vergara - 1976 - Physiological and morphological adaptability of ri

138 CLIMATE AND RICE
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DE WIT. C. T. 1965. Photosynthesis ofleafcanopies. Agric. Res. Rep. 66311-57.
‘FABUI-Lt. K. I957. Studies on temperatures of water layer in paddy fields [in Japanese. English
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‘IABLIKI. R. M. Aotil. and K. HAMoTAxl. 1972. The eliect of wind speed on the photosynthesis
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DISCUSSION
NIOnTEITI-i (Chairman): l want to make two general and three specific points about the paper.
The tirst point is related to the theme of variability in time and space which we considered in
the last session. Dr. Uchijimzfs work has been concerned with variability‘ over very short time
scales of the order of fractions of a second. and with small length scales of a few centimeters.
This is the domain in which the micrometeoroltigist has to work.
Now alter working alongside biologists for many years. l‘ve come to the conclusion that
most of them really like variability! The center point of many biological papers is a table of
results garlanded with coefficients of variation and stellar indications of significance. Physical
scientists have a dillerent approach to nature. believing that variability" in tibservations is an
admission of ignorance. to be minimized as far as possible by the application of fundamental
physical laws and concept. Some of these concepts involve probability functions to describe
variability‘ in a fonnal way.
Dr. Uchijima has shown us how micronieteorologists have been able to introduce this kind
of physical orderliness into the immense variability of weather in crops; for example. he has
used the first Law of Thermodynamics disguised as equation 21. Other equations are phenomenological.
that is. they summarize the results of many experiments in difterent crops and at
different sites in terms of clearly’ defined parameters. In contrast. crop physiology might be
described as still in a pre-Newtonian stage of development. descriptive rather than analytical.
lt is symptomatic of the subject that the physiological papers submitted to this meeting contain
so few formal mathematical relations. a vast sea of painstaking observations from which a very
few general principles seem to be faintly’ emerging.
But I am not dcnigrating the elTorts of biologists. because my second general point is this. II
the micrometeoroltigy of crops has become well paramcterized whereas crop physiology is still
passing through a more primitive stage of development. perhaps we should stop. or at least
slow down. studies of the micrometeoroltigv of crop canopies until we can make our physical
measurements more relevant to the biological side of the system. lrispired by the promising work
of people like Eichii Inoue. some of us have had a ball for the last 20 years or so, continually
refining methods tor measuring and analyzing the processes of exchange which are characteristic
of crop communities. I am convinced that what we need now is a much closer integration
of micrometeoroltigical and botanical tibscrvations. Dr. Uehijima in his paper uses only two or
three plant parameters and is concerned with only two processes. photosynthesis and transpiration.
We can see how much relevant biology is missing from this kind of exercise if we look at
the other papers submitted to the symposium dealing with water stress. cold injury. panicle
initiation. extension of pollen tubules. components of yield. etc. Microrneteortilogists should
now he getting more involved in these and other aspects of crop ecology’. For a start. 1 believe
they’ should become more concerned with the relation between the microclimale of crops and
the temperature and water potential of plant tissue. hleasurements of temperature and yvatcr
potential are central to an understanding of how the development of crop plants. from germination
to maturity’. is controlled by" their physical environment.
My specific points are these. First. I was glad to see that both Dr. Uchijima and Dr. Mitchell
have expressed irradiance in the proper units lbr a flux of energy per unit area, i.c. watts per
square meter, The photometric units (kilolux) used elsewhere are inappropriate for plant