2. Materials and methods
2
.
1
. I. Germination experiment Germination was evaluated using the Interna-
tional Rules for Seed Testing ISTA, 1976. Cot- ton seeds Gossypium barbadense L. cv. Giza 75
were soaked for 24 h in six concentrations of kinetin 6-furfurylaminopurine 0, 0.25, 0.5, 1.0,
5.0 and 10.0 mg l
− 1
before germination. Alu- minium dishes 17 cm in diameter and 3 cm deep
were used. Sand was used as substrate with pH values within the range 6.0 – 7.5, which must be
free from foreign seeds and sterilized at 250°C for 4 h to avoid infestation by fungi, bacteria or toxic
substances. It was sieved to receive reasonably uniform sand particles \ 0.05 – 0.8 mm diame-
ter, washed, sterilized and kept moistened. Fifty pre-soaked seeds were placed in each dish in a
2-cm deep sand depression made with a standard puncher. Each concentration included four repli-
cates of two dishes 100 seeds per replicate. Dishes were then incubated in a darkened germi-
nator at 30 9 1°C for 96 h, after which the per- centage of seeds which germinated was recorded
for seed viability. Seedling vigour was recorded from 10 seedlings which were randomly selected
from each dish; lengths of hypocotyl, radicle and entire seedling were measured. The 10 seedlings
were weighed immediately to record fresh weight.
2
.
2
. II. Field experiment Two field experiments were performed during
the 1993 and 1994 seasons at the Agricultural Research Center Experimental Station, Giza,
Egypt, with the cultivar Giza 75. The soil type in both seasons was a clay loam with alluvial sub-
stratum pH: 8.10; 44.1 clay; 27.8 silt; 18.9 fine sand; 4.22 coarse sand; 2.98 calcium car-
bonate and 1.82 organic matter. The field ca- pacity 0 – 60 cm was 35. Total water supply
during the growing season was about 6000 m
3
per hectare.
Each experiment consisted of 18 treatments of the following combinations: six different concen-
trations of kinetin 0, 0.25, 0.5, 1.0, 5.0 and 10.0 mg l
− 1
and three different methods of applica- tion: A seeds were soaked for 24 h in different
kinetin solutions before sowing; B cotton plants were sprayed with 480 l ha
− 1
uniform coverage of leaves at 60 and 75 DAS square initiation and
the beginning of boll filling with different kinetin solutions; and C methods A + B.
The experimental design was a randomized complete block with four replications. Seeds were
sown on March 24 and April 8 in 1993 and 1994, respectively, in plots consisting of 5 rows 3 m
wide × 4 m long. Hills were spaced 20 cm apart in rows. Plants were thinned to two plants per hill
after 6 weeks to attain plant density of 16.6 m
2
. The first irrigation was given 3 weeks after sow-
ing, and the second 3 weeks later, thereafter the plots were irrigated every 2 weeks until the end of
the season for a total of nine irrigations. Phospho- rus was applied before sowing at a rate of 24 kg P
ha
− 1
as calcium superphosphate 6.5 P. Potas- sium was applied before the first irrigation at a
rate of 47 kg K ha
− 1
as potassium sulfate 40 K 3 weeks after sowing. Nitrogen was applied
at the rate of 144 kg N ha
− 1
as ammonium nitrate with lime 33.5 N in two equal amounts,
6 and 8 weeks after sowing; each application was followed immediately by irrigation.
Ten plants were chosen randomly from the center row of each plot to determine the number
of opened bolls per plant, boll weight and seed cotton yield in grams per plant. Earliness was
estimated as the portion of the total yield har- vested in the first picking. First hand-picking took
place on 24 and 30 September and final picking on 14 and 20 October in 1993 and 1994, respec-
tively. The total seed cotton yield of each plot including 10 plant subsamples was ginned to
determine seed cotton and lint yield, lint percent- age lint percent of seed cotton, seed index g100
seeds, and lint index g of lint100 seeds. Fiber tests were made at the laboratories of the Cotton
Technology Research Division, Cotton Research Institute, Agricultural Research Center, Giza,
Egypt, at a relative humidity of 65 9 2 and temperature of 20 9 1°C. Measurements consisted
of: i fiber length in terms of 2.5 and 12.5 span length millimeters and uniformity ratio as mea-
sured by a digital Fibrograph, ii micronaire reading a combined measure of fiber fineness and
fiber maturity measured by a Micronaire instru- ment, and iii flat bundle strength expressed in
terms of strength weight ratio ‘s.w.r.’ measured by the Pressley index according to Annual Book
of ASTM Standards, D 1447-77, D 1448-79, and D 1445-75, respectively, 1979. Results were ana-
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