Abstract: Auxin regulates almost every aspect
of plant growth and development. Its intracellular
concentration is controlled by biosynthesis and
degradation. In addition, there is an “auxin pool”
that consists of the conjugates with sugars,
amino acids, and peptides. Some of the
conjugates reversely release auxin, enabling
alternative methods to regulate auxin
concentrations. Auxin concentrations are also
affected by transport. Besides the long distance
delivery through the phloem, auxin is transported
across the cell by influx and efflux carriers, from
the shoot to root with maximum concentration at
the root tip. At the root tip, the auxin flow
reverses, and shootward auxin transport occurs.
An auxin gradient formed this way is
indispensable for proper development,
maintenance of the meristem, and cell identity.
The formation of root hairs is auxin-dependent.
Auxin controls not only the initiation of root hairs
but also regulates their elongation. In
Arabidopsis thaliana, auxin accumulates in
atrichoblasts and it is supplied to trichoblasts.
Before hair initiation, randomization of cortical
microtubule arrays is observed in lettuce
seedlings. This action is promoted by auxin and
is indispensable to hair formation. Furthermore,
light promotes CMT randomization and root hair
initiation via auxin signaling. Ethylene is another
promoter of root hair formation. Ethylene affects
auxin signaling and vice versa. Interactions
between these hormones are synergistic for root
growth inhibition but antagonistic for lateral root
formation. Reactive oxygen species also
regulate various responses in plants. They play
an important role during root hair elongation,
although their precise relationship with auxin is
yet not clear.
Abstract: Auxin regulates almost every aspectof plant growth and development. Its intracellularconcentration is controlled by biosynthesis anddegradation. In addition, there is an “auxin pool”that consists of the conjugates with sugars,amino acids, and peptides. Some of theconjugates reversely release auxin, enablingalternative methods to regulate auxinconcentrations. Auxin concentrations are alsoaffected by transport. Besides the long distancedelivery through the phloem, auxin is transportedacross the cell by influx and efflux carriers, fromthe shoot to root with maximum concentration atthe root tip. At the root tip, the auxin flowreverses, and shootward auxin transport occurs.An auxin gradient formed this way isindispensable for proper development,maintenance of the meristem, and cell identity.The formation of root hairs is auxin-dependent.Auxin controls not only the initiation of root hairsbut also regulates their elongation. InArabidopsis thaliana, auxin accumulates inatrichoblasts and it is supplied to trichoblasts.Before hair initiation, randomization of corticalmicrotubule arrays is observed in lettuceseedlings. This action is promoted by auxin andis indispensable to hair formation. Furthermore,light promotes CMT randomization and root hairinitiation via auxin signaling. Ethylene is anotherpromoter of root hair formation. Ethylene affectsauxin signaling and vice versa. Interactionsระหว่างฮอร์โมนเหล่านี้มีพลังในรากยับยั้งการเจริญเติบโตแต่เป็นปรปักษ์สำหรับรากด้านข้างการก่อ ชนิดออกซิเจนปฏิกิริยายังควบคุมการตอบสนองต่าง ๆ ในพืช พวกเขาเล่นมีบทบาทสำคัญในรากผม elongationแม้ว่าความสัมพันธ์ที่ชัดเจนกับออกซินยังไม่ชัดเจน
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