Hi, Wanzhuo,

you can try to do this by change plant nutrition and growth conditions. Namely, you can try use weaker light, special combination of micro and macro nutrients etc. Good luck!

To reduce IAA levels in leaves you can use TIBA - Triiodobenzoic acid - inhibitor

of auxin transport

Sincerely Yours, Dr. V.A.Tsygankova

Thanks, V. Tsygankova. Is TIBA the transport inhibitor? If so, the use of TIBA on petiole will increase the IAA content in leaf. Is there any other inhibitor to reduce IAA content in leaf?

Dear Wanzhuo!

You can find more answers to your questions in the Internet using key words:

TIBA - Triiodobenzoic acid - inhibitor of auxin transport

Inhibitors of auxin biosynthesis

Inhibitors of auxin transport

Sinserely yours, Victoria Tsygankova

TIBA does not reduce IAA level, but increasing it, You can try to use yucasin, as potential inhibitor of IAA biosynthesis: http://onlinelibrary.wiley.com/doi/10.1111/tpj.12399/full

Or you can manipulate with activity of IAA biosyntehsis gene like TAA, YUCCA etc. Good luck!

Dear Wanzhuo!

I send you more detailed information on your questions. Please use its as keywords for search answers.

1-N-Naphthylphthalamic acid (NPA) and 2,3,5-triiodobenzoic acid (TIBA) are used as specific inhibitors of the auxin efflux.

Quercetin (a flavonol) and Genistein are naturally-occurring auxin transport inhibitors.

9-Hydroxyfluorene-9-carboxylic acid (HFCA), TIBA, and trans-cinnamic acid (TCA) are also example of Polar Auxin Transport Inhibitors. They prevent the development of the bilateral growth of the plant embryo during the globular stage. All 3 inhibitors induce the formation of fused cotyledons in globular but not heart-shaped embryo

Polar auxin transport can be regulated by reversible protein phosphorylation; protein kinases and protein phosphatases mediate the phosphorylation and dephosphorylation, respectively. A study suggests that phosphatase inhibition can alter the activities of acropetal and basipetal auxin transport.

With best regards, Victoria Tsygankova

Dear Wanzhuo!

I find information about not direct but indirect influence of inhibitors of auxin polar transport on decrease content IAA in leaves. You can see this information on keyword:

inhibitor of auxin biosynthesis in leaves.

Sincerely Yours, V.Tsygankova

Dear Wanzhuo!

Please, see also additional information confirming indirect influence of inhibitors of auxin polar transport on decrease content IAA in leaves on reference:

https://www.google.com.ua/search?q=indirect+influence+of+inhibitors+of+auxin+polar+transport+on+decrease+content+IAA+in+leaves&rlz=1C1AVSX_enUA523UA523&oq=indirect+influence+of+inhibitors+of+auxin+polar+transport+on+decrease+content+IAA+in+leaves&aqs=chrome..69i57&sourceid=chrome&espv=210&es_sm=93&ie=UTF-8#q=indirect+influence+of+inhibitors+of+auxin+polar+transport+on+decrease+content+IAA+in+leaves&start=10

With best regards, Victoria Tsygankova

In my view the best is method is by photooxidation using light sources particularly blue wavelength region.

Applying blue light for a short time causes Auxin photo oxidation and can help to reduce not only Auxines but every physiological activitity in plants.

Adding