Vergara - 1976 - Physiological and morphological adaptability of ri

32]
Physiology of water deficits in
cereal grains
J. Boyer and H. G. McPherson
SUMMARY
has a differential deet on physiological processes known to contribute
to grain yield. Drought
The recognition of such differential sensitivity and
the study of the more sensitive processes are important first steps in improving
yield during drought.
Cell enlargement is extremely sensitive to desiccation and can be affected by
the normal changes iii plant Water status which follow changes in evaporative
demand during the day. The photosynthetic activity of the leaves is considerably"
less sensitive, but any inhibition of rates during grain fill can have important
effects on agronomic yield. The lI‘&ll'lSl0CZ1lit)l1 of photosynthatc. although
diminished during desiccation, nevertheless continues even after the complete
cessation of photosynthesis. ll is unlikely. therefore. that inhibition of the
translocation process itself represents an important limitation for grain yield
during drought.
The flowering process requires a specialized set of events which may‘ be
controlled to an extent by photosyrithate supply and all enlargement. Floral developmeiit.
flowering. pollination. and fertilization represent the stages of crop
development most sensitive to drought inhibition. and much further study of
these processes is warranted.
[t is suggested that breeding for less inhibition of cell enlargement arid less
senescence of leaves during prolonged desiccation may improve the productivity
of plants under moderately dry conditions. particularly in cereal crops. Breeding
and managing crops to improve root systems and reduce water use may‘ zdso
provide a means of increasing grain yields. In the long term. it may be possible
to reduce the inhibition of photosynthesis by desiccation. but more fundamental
knowledge is needed for this to be assessed.
lNTR()DUC TlON
The formation of grain in crops requires the contribution and good timing of
a number of central physiological processes. Photosynthetic material must be
produced. and high yields require the development of a large. highly active
photosynthetic surface. Photosynthetic products must then be moved to the
seed. Carbohydrates. largely as sucrose. and nitrogen compounds. probably
as amino acids. are the main transport forms and they are combined and modi-
J. Bqier‘. Department of Botany‘. Llniversity of Illinois. Urbana. Illinois. USA. H. J. ilfCp/ITFSOH
Plant Physiology‘ Division. Division of Scientific and Industrial Research (DSIR). Palmerston North.
New Zealand.