| Budget Amount *help |
¥2,300,000 (Direct Cost: ¥2,300,000)
Fiscal Year 1998: ¥600,000 (Direct Cost: ¥600,000)
Fiscal Year 1997: ¥1,700,000 (Direct Cost: ¥1,700,000)
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| Research Abstract |
Attention was focused on roles of calcium in gravitropism of roots. We also found that the interaction of Ca^<2+>/H^+ in the apoplast of root tips may be involved in transmission of the gravity signal In the gravitropism of Zea primary roots. However, actions of calcium remains unknown, because factor(s) mediating the gravitropic response remains to be determined.
To study factor(s) and actions of calcium, movements of diffusible IAA and contents of cell wall-bound IAA in apical region of gravistimulated roots of Zea (cv. Golden Cross Bantam 70) were examined by using the indolo-alpha-pyrone method and flow-injection analysis. The content of diffusible IAA in 1-2-mm and 2-3-mm sections increased transiently, reaching a maximum at 20 min and 40 min after gravistimulation, respectively. However, 0-1-mm sections had little diffusible IAA, On the other hand, the content of cell wall-bound IAA showed transient decrease with a nadir at 20 min in only 0-1-mm sections. These results indicate that diffusible IAA may be transported basipetally from the tip to the elongation zone in response to gravistimulation and that cell wall-bound IAA may be source of diffusible IAA.Thus, we suggest that the reversible reaction between cell wall-bound IAA and diffusible IAA may be involved in the signaling processes of gravity.
Furthermore, we found that the increase in the content of diffusible IAA in the 2-3-mm sections was prevented by treatment the root cap with 5 mM EGTA, To study effects of calcium on the reversible reaction of IAA in vitro experiments are in progress using 0-1 mm section.
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