centrations ranging from 0.25 to 5.0 mg l
− 1
and application methods A and C resulted in a slight
numerical reduction in yield earliness.
3
.
5
. Fiber properties Kinetin application did not significantly affect
fiber length parameters 2.5 and 12.5 span lengths and uniformity ratio, micronaire reading or flat
bundle strength in either season, with only one exception, where micronaire reading increased
compared with the untreated control in 1994. This increase in micronaire reading was significant when
applying concentrations of kinetin ranging from 0.5 to 10.0 mg l
− 1
. The mean values of these characters tended to slightly increase by applying kinetin at
different concentrations when compared with the control. The kinetin application methods did not
affect fiber properties in either season, with two exceptions where fiber 12.5 span length and flat
bundle strength increased when applying method B as compared with method A. Fiber 2.5 and 12.5
span lengths, micronaire reading and flat bundle strength tended to increased slightly by using
application method B, followed by application method C, compared with application method A,
while length uniformity ratio did not follow a definite trend.
3
.
6
. Interactions Interactions were noted between kinetin concen-
trations and kinetin application methods regarding their effects on seed cotton yield per plant and seed
cotton and lint yields per plot in 1994 Table 3, but not on other measured characters. Favourable
effects for 5.0 mg l
− 1
kinetin concentrations on seed cotton yield per plant and seed cotton and lint
yield per plot, were more obvious when kinetin application method C was used.
4. Discussion
4
.
1
. Seed 6iability and seedling 6igour The stimulatory effect of kinetin application on
seed viability and seedling vigour could be at- tributed to its favourable effects on synthesis of
RNA, proteins, and enzymes, causing a general metabolic advancing or priming to occur Moore,
1989. Actually, cytokinins might be rapidly incor- porated into micromolecules such as RNA. On the
basis of their findings, it could be stated that cytokinins promote RNA and protein synthesis
and that exogenous cytokinins often have highly localized effects when applied to whole plants and
plant organs Moore, 1989. The stimulative effect of kinetin on germination and seedling vigour
observed in the present study agrees with the findings of Bozcuk 1990 and Kabar 1990 with
cotton and Singh and Amritphale 1993 with soybean.
4
.
2
. Yield components Rodgers 1981 made a comparative analysis of
retained and naturally abscising cotton fruits and found that abscission was negatively correlated
with the concentration of cytokinins. Therefore, foliar applications of this chemical to cotton plants
should reduce flower bud and young boll shed and promote fruit growth. Mayeux 1985 showed that
Burst a commercial cytokinin product applied at early bloom or applied at mid bloom significantly
increased the boll set and fruiting of cotton plants. Similar findings were obtained by Oosterhuis et al.
1997. The positive response of boll weight to kinetin application might be explained by the
physiological, metabolic, and biochemical effects of kinetin. In this respect Gadallah 1995 found that
application of kinetin at 10, 50 or 100 mg kinetin l
− 1
to castor bean Ricinus communis plants increased the stability of cell membranes, chloro-
phyll, soluble sugars, soluble proteins and dry matter content. The present results consistent with
those obtained by Mayeux 1985 and Abdel-Al et al. 1989. Namken 1984 and Abdel-Al et al.
1989 also found little effect of cytokinin on lint percentage. Abdel-Al et al. 1989 found similar
results, concerning the positive response of seed index to kinetin application. The observed increase
in seed and lint indices due to kinetin application could be attributed to its stimulated action on auxin
synthesis in fertilized ovules Sandstedt, 1971 and this makes them more able to attract more nutrients
Mayeux, 1985 which would enhance their growth leading to initiation and development of
greater number of fibers per seed Skoog and Armstrong, 1970.
4
.
3
. Yield These results may be attributed to the promot-
ing effect of this substance on numerous physio- logical processes, leading to an improvement in
all yield components. Guinn and Brummett 1993 stated that cytokinins have been reported
to increase stomatal aperature and stimulate photosynthesis. Bauer and Cothren 1986 indi-
cated that an increase in photosynthesis greatly increased flowering, boll retention, and yield.
Parker and Salk 1990 and Hedin and McCarty 1994a reported that kinetin increased seed cot-
ton yield. Namken 1984 also found that cy- tokinin applications increased lint cotton, while
Dhopte and Lall 1987 found that a foliar spray of 10 mg l
− 1
kinetin at the flowering stage, in- creased dry matter production, decreased boll
shedding and increased seed cotton yield.
4
.
4
. Yield earliness Namken 1984 found that there were no sig-
nificant differences in earliness due to cytokinin treatments.
4
.
5
. Fiber properties Namken 1984 found that there were no sig-
nificant differences
in fiber
properties mi-
cronaire, length, uniformity, and strength due to cytokinin treatments. Abdel-Al et al. 1989
found that application of cytokinin had no sig- nificant effect on micronaire reading and flat
bundle strength. Hofmann and Else 1989 found that kinetin had no significant effect on fiber
quality.
5. Conclusions
