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THE EFFECTS OF WATER DEFICIENCY ON THE PHYSIOLOGY AND YIELD OF MAIZE AND BARLEY
Water is one of the important environmental factors that effect plant
growth. In Taiwan, the cultivations of field crops are often failed by
the water stress due to the geographical and weather conditions.
Therefore, it is necessary to understand the response of plants under
water stress condition, and the relationship between drought-resistance
and yield capacity for the purpose of improving the rotation system of
In the present experiment maize and barley were used as the
materical. The following physiological and biochemical programs were
1.The growth and physiology of photosynthesis of expanded leaves.
2.The significance of the changes in amount of sulutes inside
expanding leaves and the growth functions under the condition water
deficits and rewatering after water shortage.
3.The observations of the root/shoot ratio and the leaf size by using
soil-sand culture under eaterstress condition. Moreover, to find
out the possible factors which inhibited the leaf elongation
4.To search for the effects that water stress exerted on yield
component of various crops.
The results were summarized as follows:
1. The water potential and osmotic potential of expanded leaf of maize
and barley displayed significant diurnal varivation under control
and mild stress (-0.8 ~ -1.5 Mpa). The diurnal pattern of the
osmotic potential of expanded leaf of all varienties, almost
paralled to those of leaf water potential, thus maintaining the
turgor level, thus because, the concentration of the major solutes
of expanded leaf of all varieties, also exhibited a significant
diurnal variations, and weren''t much changed by mild stress. The
only change cuased by mild stress was starch/sucrose partitining
2. The photosynthetic rate, leaf conductance and leaf relative water
content of each variety decreased with leaf water potential; and
varied with varieties. The physiological responses could be used
as indicators for selecting drought resistance.
3. Under moderate stress (-1.2 - -1.5 Mpa), the osmotic potential of
expanded leaf of all varieties showed adjustable in various degree.
The more drought-resitant strains, like maize TN11 and barley CB15,
have much more solutes than those non-resisteant strains, like maize
TNG351 and barley CH2. Therefore, osmoregulation can be maintaned
and allowed to continue expansion growth under growth-inhibiting
drought condition as well.
4. Leaf elongation is very sensitive to water shortage, and was
inhibted under mild stress; For maize TN11, TNG351; barley CH2,
CB15, leaf elongation ceased when predawn declined to -1.3 Mpa,
-1.1 Mpa; -1.1 Mpa, -1.45 Mpa. Since the selongation of leaves
os ,pre semsotove tp tje water supply, it gave a significant
influence to the yield capacity, and it is so easily to dectate, so
the response of LER (leaf elongation rate) to water stress, has
become a useful indicator for screaring drought-resistant plants.
5. The Li+, Na+, K+ contents of the elongation leaves kept constant
under the water stress condition. The orgainic compounds were
accumulated significantly at early drought stage, and give a
considerable influence to the osmotic adjustment. The earliest
response to water deficits was the accumulation of soluble sugar
content, then, the free amino acid. All these material were
involved in osmotic adjustment. When the condition of water supply
get worse, the extension growth of leaves had almost creased and
metabolism of sugar and nitrogen compounds were also influenced.
This showed that the necessity of growth is much related with the
metabolism of feed back control.
6. As for the restoration of rewatering after water shortage, it give
a corelation with crop varieties. The result showed, when the
variety gave more drought-resistance, the leaves related with yield
and physiological reactions, restored more healthy and stronger.
7. From the soil-sand culture, the result showed that the shoot growth
of the plant under the water stress condition was reduced more than
the root growth. This indicated that root-shoot ratio are increased
by water stress. On the other hand, the cell wall extensibility
were also decreased gradually after a long term of drought.
Therefore, water deficits could also changed the leaf biophysical
8. The important factors which effects the yield components are the
time of water shortage and the degree of water stress. If the
flower buds of plants were initaited under various water stress
condition, then the grains per spike and panicle weight would be
decreased, However, the plant height and panicle length were not
influenad, consequently, the water are more short, the yield are
more lower. When the period of plant internode elongation was under
water shortage condition, the plant height was decreased
significantly, the grains per spike and the weight of per 100 grains
were also decreased. During the flowering stage, the water stress
would influence the yield of grains per spike, the flowering date
both barley and maize were delayed as well. In the milk-riping
stage, the weight of per 100 graing would be effected by water
stress, the seed filling period was also getting shorter.
米TNG351；大麥CH2、CB15 分別於黎明前葉片水分潛勢（predawn ψ ） 為-1.3Mpa，
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