RA 00015.pdf - OAR@ICRISAT

Figure 22. Transverse section of the leaf lamina
of pearl millet hybrid HB 3 showing
the characteristic bundle sheath cells
of the C4 plant.
cells). Surrounding these are the smaller mesophyll
cells, also containing chloroplasts. Marked
cultivar differences in the concentration of
chloroplasts in the bundle sheath cells were
noted.
Effects of Drought-screening Treatments
on Crop Growth and Yield
In order to learn more about the effects of
artificial stress treatments used in screening for
drought resistance, detailed measurements of
crop growth and yield were carried out on
irrigated and on stress treatments during the hot
dry season. The stress treatments used were a
mid-season stress (from 30 to 64 days after
emergence) and a terminal stress beginning at
flowering (48 days after emergence).
Crop duration was shortened by 10 days and
the total crop growth reduced by about 30
percent in the terminal stress treatment (Fig 23).
The mid-season stress caused a marked reduction
in crop growth during the treatment
period, as well as an apparent depressive effect
on growth rate following termination of stress.
Total dry weight and maximum leaf area index
achieved in this treatment were only approximately
60 percent of those in the control, and
crop maturity was delayed more than 20 days.
Grain yields, similar in both stress treatments,
were approximately 45 percent of those in the
control (Table 20). The way in which yield
reduction occurred, however, differed between
the two stress treatments as different yield components
were affected by the different timing of
the two treatments.
Yield reduction in the terminal stress treatment
occurred because of the failure of the late
tillers to develop (compare the differences in
panicle numbers between this treatment and the
control at 64 days and at maturity, Table 20) and
because of a reduction in size of the grains filled
under stress. Yield reduction in the mid-season
stress treatment was due entirely to a reduction in
the productivity of the average panicle. Tillers
whose development was interrupted during the
stress resumed growth after the stress was terminated
(again compare panicle numbers at 64 days
600
400
200
Drought
-period
Drought period
Control
Terminal stress
40 80 120
Days after seedling emergence
L.S.D.
(0.05)
Midseason
stress
Figure 23. Effects of stress treatment on crop
dry-matter accumulation. Arrows indicate
time of application of drought
stress. The mid-season treatment was
relieved on Day 65; the terminal stress
treatment was not relieved, as the crop
had senesced by Day 80.
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