The following hormone is anti auxin
a. NAA b. IBA c. Cytokinin d. Gibberellin
Answers
. First idea of plant hormones was given by Von Sachs "organ forming substance."
2. Ist Plant hormone discovered by F.W. Went was Auxin but term hormone was given by Starling & Phytohormone by Thieman.
Chemicals which are acts as natural Phytohormones are called as synthetic growth hormones. Synthetic Auxins
a-& b-NAA, 2, 4-D, 2, 4, 5-T, IPA PAA, IBA Maleic hydrazide (MH).
NAA-Napthalene acetic acid
2-4-D - 2, 4-Dichlorophenoxy acetic acid.
2, 4, 5- T - Trichloro phenoxy acetic add.
IPA - Indole propeonil pyruvic acid
PAA - Phenyl/phenoxy acetic acid·
Factors related to growth of plant
Auxins
Charles Darwin & F. Darwin (1880) was the first one to study phototropism. They observed coleoptile bending in Canary grass (Phalaris). Wrote, Book "Power of movements in plants" Term"Stimulus" By Darwin.
Boysen & Jensen 1910: Experiments on oat (Avena sativa) Plant.
In the first experiment he removed the coleoptile tip and then replaced it on stump.
On providing uniiaterallight the coleoptile tip gave positive curvature.
They observed that if gelatin inserted between the tip & cut stump, then coleoptile bends towards the unilateral light. If mice were inserted then coleoptile fail to phototropism.
Material substance term for growth hormone was given by him.
Paal: Demonstrate that when the cut tip was replaced on cut end (stump) eccentrically (asymmetrically) it cause bending even in dark.
If coca butter or platinum foil inserted there is no curvature observed.
Idea of unequal distribution of growth substance given by Paal. Large amount of substance found on shaded side.
F.W. Went (1928): Went isolated the growing tip of Avena sativa on agar plate & perform Agar-block experiment.
He give name auxin to growth substance, thus credit of Auxin discovery goes to F.W. Went.
He also found that the curvature (bending) in Avena coleoptile is proportional, with in limits to the amount of Auxin in Agar - block. This test was named as Avena curvature-test (Bioassay of auxin). Went found that 27% auxin present on illuminated side & 57% on the dark side. (About 16% auxin lost on illuminated side & rest transferred to base) Transport of natural Auxin is basipetal & polar type.
(Synthetic ® Auxin = A polar transport)
Kogl & Hagensmit (1931): Isolated an active substance from urine-of pellagra patient which was called as Auxin - A or chemically auxenotriolic acid (C18H32O5).
Later a similar substance was isolated from corn grain oil and was named as Auxin-B or Auxenolonic acid. (C18H30O4).
Again Kogl, Erxleben & Haagen Smit 1934 - Isolated another substance from human urine and named as Heteroauxin
(IAA-C10H9O2N) by Thimann,
Auxin from Rhizopus was obtained by Thimann.
Auxin biosynthesis occurs by tryptophan amino acid in the presence of Zn++ ion.
Degradation or oxidation of Auxin
Enzymatic (by IAA oxidase)
Photo-oxidation
Now IBA (Indole Butyric acid) have been also isolated from plants (natural auxin) but IAA is most widely found auxin in plants.
The compounds which can be converted into auxin are called as auxin precursor, whereas the compounds which inhibits the activity of auxin are called as antiauxins.
Indole Acetic Acid
Natural auxins: These are naturally occurring auxins in plants and therefore; regarded as phytohormones. Indole 3-acetic acid (IAA) is the best known and universal auxin. It is found in all plants and fungi.
The first naturally occurring auxin was isolated by Kogl and Haagen-Smit (1931) from human urine. It was identified as auxin-a (auxenotriolic acid, C18H32O5).s Later, in 1934 Kogl, Haagen-Smit and Erxleben obtained another, auxin, called auxin-b (auxenolonic acid, C18H30O4) from corn germ oil (extracted from germinating corn seeds), and. heteroauxin from human urine. Heteroauxin (C10H9O2N) also known as indole-3-acetic add (IAA), is the best known natural auxin, Besides IAA, indole-3-acetaldehyde, indole -3-spyruvic acid, indole ethanol, 4-chloro-idole aerie acid (4-chloro-IAA) etc., are some other natural auxins.
Explanation:
please mark as brainlist
give me answer in this question