| Effects of phytohormones and relative enzymes on initiation and elongation of cotton fiber cells were studied by using two fiber mutants, super short fiber mutant (Lil) and fiberless mutant (fl). The results were shown as follows.1. Restriction mechanism for fiber elongation of Lil mutant grown in Held There were abnormities of ultra structure in 9 DPA fibers of Lil mutant whencompared with wild type: thinner cytoplasm, less functional organelles such as Golgi body and endoplasmic reticulum, ect, and more starch grains. Energy form was stored as starch in early period instead of transformed to polysaccharide during the fiber elongation, which might result in the stagnation of fiber elongation.In the fiber of Li/ mutant grown in field, hormone content and its peak and vale points during the elongation presented an abnormal curve. For the content of GA3, the mutant had a flat-trend change, while the wild type had a parabola change. For the content of IAA, the mutant was lower content than the wild type. After fiber elongation stopped, a peak point of IAA occurred at 12 DPA for the mutant, but had two peaks at 6 DPA and 15 DPA for the wild type, which corresponded for the dates of fiber fast elongation. For the ZRs content, although the mutant had the similar change trend to the wild type, the content was only 1/15 of the wild type. This indicated that shortage of ZRs, low increase of GA3 and abnormal peaking time of IAA might be the reasons of restriction to elongation of the mutant, and this kind of restriction could be recovered partly by exogenous hormones in culture media.2. Recovery mechanism of restriction to fiber elongation of Li 1 mutant in vitroFiber length of the mutant and the wild type were 3.41 mm and 7.23 mm in GA3+IAA media and increased significantly at 5% level than fiber in check media, which were 76% and 24.3% of the field fiber length. There was a cooperation effect between GA3 and IAA on the fiber elongation, but the effect was 3.1 times more in the mutant ovule than in the wild type ovule, suggesting that cooperation effect of the two hormones could release the restriction of fiber elongation caused by some defectsof the mutant in some degree. But the restriction of fiber elongation still could not be completely released because of the genetic inhibitory factor(s) in the mutant.3. Cooperation of hormones and enzymes on fiber elongation of the mutantIn field, IAA content in the mutant fiber peaked at the end of fiber elongation, while IAA oxidase activity maintained to rise and peak in later period of fiber elongation just like the wild type did. In vitro, IAA content increased both in mutant and wild type, while IAA oxidase activity in the mutant was more calmed than in the wild type. So it can be detected that many kinds of factors acted on the release of restriction in the mutant fiber elongation, that is, high content of GA3, IAA and ZRs, and low activity of IAA oxidase made the mutant a progress in fiber elongation.4. Fiber-like callus of mutant in BT media with GA3The mutant ovule in BT media with GA3 could produce a kind of callus covered with fiber-like cells, which occupied about 10% of all bottles. This cell was a multi-cell fiber and sometime had several black dots on its surface like glands on stem and leaf of plant in field. Many microiubules around the plasmalemma were founded in these cells after culture for 21 day, which characterized second wall deposition.This kind of multi-cells often appeared in BT media with GA3. GA3 was thought to partially break the restriction in fiber initiation in the mutant and play an important role in the multi-cell formation. It was presumed that some special genes, which kept silence in field, became activated in vitro, and stimulated the original fiber cell to further separation.5. Effect of hormones and enzymes on fiber initiationLow GA3 and ZRs content made the mutant ovule no fiber initiation. Low POD and IAA oxidase activity helped to fiber initiation of the mutant, while high IAA oxidase activit...
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