Sugar demand, not auxin, is the initial regulator of apical dominance For almost a century the plant hormone auxin has been central to theories on apical dominance, whereby the growing shoot tip suppresses the growth of the axillary buds below. According to the classic model, the auxin indole-3-acetic acid is produced in the shoot tip and transported down the stem, where it inhibits bud growth. We report here that the initiation of bud growth after shoot tip loss cannot be dependent on apical auxin supply because we observe bud release up to 24 h before changes in auxin content in the adjacent stem. After the loss of the shoot tip, sugars are rapidly redistributed over large distances and accumulate in axillary buds within a timeframe that correlates with bud release. Moreover, artificially increasing sucrose levels in plants represses the expression of BRANCHED1 (BRC1), the key transcriptional regulator responsible for maintaining bud dormancy, and results in rapid bud release. An enhancement in sugar supply is both necessary and sufficient for suppressed buds to be released from apical dominance. Our data support a theory of apical dominance whereby the shoot tip’s strong demand for sugars inhibits axillary bud outgrowth by limiting the amount of sugar translocated to those buds. It is commonly accepted that the plant hormone auxin mediates apical dominance. However, we have discovered that apical dominance strongly correlates with sugar availability and not apically supplied auxin. We have revealed that apical dominance is predominantly controlled by the shoot tip’s intense demand for sugars, which limits sugar availability to the axillary buds. These findings overturn a long-standing hypothesis on apical dominance and encourage us to reevaluate the relationship between hormones and sugars in this and other aspects of plant development. Old topic, new story. Everything is possible.
Well, my old doctor left Kaiser, and I was assigned to a new comer, Dr. P. I haven't seen him, but I decided that I don't want him to be my primary care doctor. Why? I had a routine physical last week, and Dr. P called me about the blood test results, bad results to him. I was puzzled. I never had bad test results before, and less than two years later and I am DOWN HILL to hell? I don't believe it. Hey, I am a scientist, and I can think and web surf. I have a healthy life style. If I have to change my life style, I will go have steak for dinner every day from now on! Bye, Dr. P . I will try another doctor... Blood sugar during 24 hours. Wiki link on blood sugar is at http://en.wikipedia.org/wiki/Blood_sugar#Units To unders tand n on-f ast ing test result: http://health.nytimes.com/health/guides/test/hba1c/overview.html http://en.wikipedia.org/wiki/Prediabetes How to Lower Blood Sugar Naturally http://www.lifescript.com/health/centers/diabetes/articles/10_tips_to_lower_blood_sugar_naturally.aspx Cholesterol: Top 5 foods to lower yournumbers http://www.mayoclinic.com/health/cholesterol/CL00002
标签: sugar
