Thursday, August 7, 2014

Do Lithops Use Abscisic Acid? You bet!

What's this? Alert Gardener Jim (who is growing more alert all the time, it seems!) sent me this intriguing snippet from the journal Science and I couldn't help think of our hardy Lithops (and other mesembs and cacti, too):

ABA Tells Roots To Stop And Then Grow   Jason D. Berndt  Science  6/6/14
"Plants initially grow a primary vertical root. The primary root then puts out horizontal lateral roots, which help to anchor the plant and take up water and nutrients from the soil. But to make the most of precious resources, plants use the hormone abscisic acid to stop lateral roots from growing in times of drought. Zhao et al. found that after a time, plants resume lateral root growth. This process paradoxically also uses abscisic acid, which binds to a different receptor and triggers changes in the expression of genes involved in resuming lateral root growth."
Sci. Signal. 7, ra53 (2014).
Lithops Abstract, MR
 Lithops guardians have noted how our favorite mesembs keep a sturdy tap root regardless of weather and soil conditions. And most of the time, that's all they have. But when moisture appears in the form of brief rains or heavy fog/dew, a Lithops can grow fine lateral roots in an astoundingly short time. The new roots take up the available water, then degrade as conditions go back to normal (bone dry). And now we know how that happens!

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