Original£ºCotton Science£¬2006£¬18(2)£º99-103
Effects of Calcium and Auxins on the Initiation Abstract£ºThe effects of Ca2+ and auxins on root growth of cotton ( Gossypium hirsutum L.) were studied. Cotton seedlings were cultured in two layers of filter paper adhered on glass boards with the lower 2 cm dipped in water and grown in growth chamber at (25 ¡À 1)¡æ. Agar solutions containing test concentrations of Ca(NO3)2, indole butyric acid (IBA), Ca(NO3)2 + IBA, Ca2+ antagonists or calmodulin (CaM) antagonists were pasted on the joint between seedling hypocotyl and radicle, respectively. Treatments with 50 mg¡¤L-1 Ca(NO3)2 and 5 mg¡¤L-1 IBA promoted lateral root initiation (LRI) by 14.8 and 29.6 %, but retarded primary root elongation (PRE) by 13.4 and 8.3%,respectively. The combination of 50 mg¡¤L-1 Ca2+ + 5 mg¡¤L-1 IBA showed synergistic effects as the LRI was 33% higher than the control, while the PRE was close to the control, but much higher than that treated with only Ca(NO3)2 or IBA. The PRE, LRI and free CaM content were inhibited by treatment with 3-10 mg¡¤L-1 LaCl3 (Ca2+ª¬inhibitor), 3-10 mg¡¤L-1 EGTA (calcium chelated agent) and 3-10 mg¡¤L-1 TFP (CaM antagonist). Treatment with 5 mg¡¤L-1 IBA enhanced indolacetic acid (IAA) in the basal radicle segment, repressed IAA and GAs in apical and middle segment of radicle, increased CTKs (cytokinin) content and decreased IAA/ CTKs in all segments of the radicle. Treatment with 3-10 mg¡¤L-1 TIBA reduced CTKs in the whole radicle, IAA and IAA/ CTKs in basal and middle segments, and increased IAA content as well as IAA/ CTKs in radicle apex, which might have contributed to its inhibition of LRI and enhancement of PRE.
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