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The results showed reduction in chlorophyll content (Fig.1
a) and leaf area (Fig.1 c) of plants
subjected to delayed sowing. The role of chlorophyll and leaf area in
photosynthesis is well known. Leaf is a major plant organ where all
photosynthetic activities take place, and photosynthesis is the
process by which radiant energy from the sun is converted into
chemical energy necessary for vital functions of living organisms.
The reduction in leaf area and chlorophyll contents in plants may
affect the photosynthetic activity of plants adversely. The end
product of photosynthesis is utilized by man as the cereal grain the
yield of which was reduced in the present experiment due to late
sowing of the crop (Fig.1 c). The reduction
in chlorophyll may be due to enhanced chlorophyllase activity (Garcia
et al. 1987) due to rise in temperature. But according to others
(Ashraf and Khan 1994; Ashraf, Azmi et al. 1994; and Kuroda et al.
1990) the reduction in chlorophyll may be due to higher peroxidase
activity and accumulation of some phenolic compounds which might
occur in the late sown crop due to temperature (25-35C) favourable
for them. As a result of reduced leaf area the crop intercepted less
photosynthetically active radiant energy resulting in reduction in
the grain yield (Ashraf et al. 1989): our results supported this
conclusion (Fig.1 c).
It has been suggested that in wheat the increase in the rate of grain
growth, due to higher temperature experienced by late sown crop, does
not compensate for the loss in grain yield caused by reduced duration
of grain growth (Bagga and Tandon 1991). The ideal condition would be
to develop varieties having faster rates of grain growth in a shorter
period. Since the rate of grain growth (increase in weight) is
dependent on starch forming enzymes, with a narrow range of
temperatures (15-30C) for activity, large differences in grain growth
rate are not expected among wheat varieties with similar sink size.
Improvement of wheat genotypes for faster rates of grain growth would
therefore, be restricted within narrow limits. The duration of the
grain amenable growth period, on the other hand appears to be of
great relevance since a number of wheat varieties are known to
maintain relatively longer durations of grain growth under increasing
temperatures. Bagga and Tandon (1991) suggested the use of medium to
long duration varieties for late sowing which is quite in line with
the above contention.
References
Arnon DT (1949) Copper enzymes in isolated chloroplast.
Poly-phenoloxidase in Beta vulgaris. Plant Physiol 24: 1-
15.
Ashraf MY and Khan AH (1994) Characterization of induced high
temperature chlorophyll mutant of rice (Oryza sativa L). Sci
Intl 6(1): 73-75.
Ashraf MY, Azmi AR, Khan
AH and Ala SA (1994) Effect of water stress on total phenol,
peroxidase activity and chlorophyll contents in wheat. Acta Physiol
Plant 16(3):185-191.
Ashraf MY, Khan AH and
Azmi AR (1992) Cell membrane stability and its relation with some
physiological processes in wheat. Acta Agron. Hung. 41 (3 -4):
183-191.
Ashraf MY, Baig NA and
Baig F (1989) Response of wheat (Triticum aestivum L.) treated
with cycocel under water stress conditions. Acta Agron Hung 38(3-4):
265-269.
Bagga AK and Tandon JP
(1991) Productivity of wheat under late sown condition. A report on
collaborative work, In: Plant Physiology Research at IARI, Division
of Plant Physiology, IARI New Delhi. pp. 31-40.
Garcia AL, Torrecillas A,
Leon A and Ruiz-Sanchez MC (1987) Biochemical indicators of the water
stress in maize seedlings. Biol Plant 29: 45-48.
Kuroda M, Ozawa T and
Imagawa H (1990) Changes in chloroplast peroxidase activities in
relation to chlorophyll loss in barley leaf segments. Physiol Plant
SO: 555-560.
Penelia JR, Bagga AK and
Wasnik KG (1993) Effect of late sown conditions on productivity and
nitrogen status in wheat. Indian J. Plant Physiol 36:
178-184.
Steel RGD and Torrie JH
(1980) Principles and procedures of statistics. MeGraw-Hill, New
York.
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