Vergara - 1976 - Physiological and morphological adaptability of ri

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Carbon dioxide and yield of rice
S. Yoshida
SUMMARY
of carbon dioxide on growth and yield of rice were examined from three
Effects different aspects: (l) effects of CO_- on photosynthesis growth, and yield. (2)
CO_ dynamics in field photosynthesis. and (3) CO; cnrichmcnt as a tool in analysis
of yicld tori-nation.
Carbon dioxide enrichment experiments showed that the optimum concentration
for growth and yield of rice lies between 1,500 and 2.000 ppm CO_. Severe
CO_- delicits occur around photosynthetic surfaces of a rice crop when active
photosynthesis proceeds under high solar radiation. Paddy soils release CO_- into
the atmosphere. ranging from 3.9 to 5.? g - m~ . day‘ under flooded conditions and
from 6.0 to 8.6 g - m-l - day-t under drained conditions. The contribution of soil
CO; to gross photosynthesis was estimated at 6% for flooded soil zmd 7% for
drained soil. CO, enrichment before and after flowering demonstrated that at
Los “altos total grain number per unit of land area is more limiting to grain yield
than to grain lilting. The critical time for determining number of grains at Los
Bafios appears to lie within the period between neck-node differentiation and
spikelet differentiation (about 33 to l4 days before flowering).
INTRODUCTION
Most crop species respond to higher carbon dioxide concentrations than to
ambient air C0, concentration. Consequently‘, in crops like vegetables, CO,
enrichment has become one of the most spectacular trays of increasing yields in
enclosed environments such as glasshouscs and plastic enclosures (Wittwer and
Robb. 1964). CO, enrichment in such environments not only increases crop
yields but also economic returns, This is however. not true for grain crops such
as rice and “the-at. Technological and economic problems do not permit use of
CO; enrichment in grain crops. We do find that the CO; enrichment technique
is a useful tool to analyze processes that limit yield formation.
I shall examine the effects of C0, on growth and yield ofthc ricc plant from
three different aspects; (l) effects of CO, on photosynthesis, grovrth, and yield;
(2) CO1 dynamics in field photosynthesis; and (3) CO; enrichment as a tool in
analjrsis of yield tbnnation.
S. lbshlda. Plant Physiology Department. lntemational Rice Research Institute (lRRl). Los Bafios
laguna. Philippines.