Vergara - 1976 - Physiological and morphological adaptability of ri

RICE GROWTH IN DIFFERENT ENVIRONNIENTS 447
TANAKA, A, and B. S. Vl-TRGARA. I967. (“rrowth habit and ripening of rice plants in relation
to the environmental conditions in the Far East. Pages 2642 in Symposittm on problem in
development and ripening of rice grain. Int. Rice Comm. Newsl. (Spec. Issue).
\I'ERL‘IAR.A, B. S., T. T. CHANG, and R. LILIS. I969. The flotvering response of the rice plant to
photoperiod. Int. Rice Res. Inst. Tech. Bull. 8. 31 p.
\-'1:Rc,uz_/~._ B. S.. A. TANAKA, R LILIS. and S. PL-"Rixximmtywo. 1966. Relationship between
growth duration and grain yield of rice plant. Soil Sci. Plant Nutr. 12:31-39.
DISCUSSION
EVAXS (Chairman): 'l‘anaka‘s paper emphasizes the litany different seasonal sequences to
which rice crops are exposed and the many patterns of growth and development these give rise
to. This leads him to conclude with the important point that phy1otron studies of the eITect of
climatic factors at particular stages of the life cycle will be of little value unless given to plants
which have experienced the full sequence of conditions relevant to the problem. It is a timely
yvaming, but there is no reason why the relevant sequence of conditions cannot be applied in
phytotrtin experiments. as Raper has shown in his work on tobacco in the Raleigh phytotron.
in which he has successfully “facsimilated" field crops.
Another important point to be made in relation to Tanakas paper is that even for a given
cultivar. whether source or sink, or reproductive or ripening phase conditions, is more limiting
to yield depends to a great degree on the sequence of seasonal conditions experienced by the
crop during its development. The cultivar best adapted to a particular locality and season is
the one in which the capacities of source and sink approach their potential limit and are in
balance under that sequence of conditions. At another season. or in another environment.
source and sink may be out of balance in that cultivar. From this it follows that the use of
single cultivars over a very wide geographical range may characterize only the early stage of the
Green Revolution. which must eventually come to terms with the need for closer local adaptation.
TAKAHASHI: Supposing everything is available. what is the ideal growing period for ideal
plant growth of a best variety"?
.=l. Tana/cu: So far as available information concurs. I prefer to have varieties with a duration
of less than 100 days. planted at close spacing so that the canopy closes up as early as possible,
and do not have the vegetative-lag phase.
NIUIL-VFA: In terms of expressing grain yield on a yearly basis. which type of gTOWIII pattern
do you think is most desirable?
A. Yhnaku: Iyly answer is the same as that to Dr. 'I'akaha.shi's question.
ORA: How can you determine when the lag phase starts?
A. Tameka: By the maximum tiller number stage.
DF. DATT-x: The period from flowering to harvest is about 30 days in high temperature situations.
It is even shorter where moisture is limiting. such as in the upland rice. Is this something
we have to live with or can breeders do something about this problem?
A. Tunakti: I do not know whether it is possible. but I think it is worth trying.
GHILDYAL: In India we have two situations. either the monsoon is delayed or it stops early.
What wtiuld be the best rice growth pattern for these two situations’?
:1. Tanaka: ‘l-Vith unreliable rains. long duration. photoperiod-sensitive varieties an: able to
adjust their growth pattern. depending upon rainfall.
LOMOTAN : In Fig. 4, areas in the East Visayas of the Philippines and the whole of Mindanao
were not included. Does this mean that rice is grown in thee areas at all times of the year‘?
.»l_ Tflfiélktl.‘ Figure 4 was compiled by .\'Ir. Kung of FAO quite some years ago. It docs
not show exact situations today. it was used to show diversities.
EVANS: In your paper you talked only about an optimum leaf-area index which I think really
applies to the old taller varieties. Vfith the modern ones we can get very high leaf-ma indices
without any decrease in crop growth.