This journal is about research on phototropism, hormone auxin and the

identification of the phototropin photoreceptors. Phototropism is directional growth in

which the direction of growth is determined by the direction of the light source. Positive

phototropism is a growth towards a light source, while growth away from light is called

negative phototropism. Most plant shoots exhibit positive phototropism, while roots

usually exhibit negative phototropism. Different organs of the plant may exhibit different

phototropic reactions to different wavelengths of light. The light stimulates the movement

of auxin to the shaded side of the hypocotyl. Phototropism is caused by differential

carotenoid-mediated auxin inactivation. carotenoids (proposed phototropism

photoreceptors) participate in photoinactivation of auxin.Phototropism is strongest

toward blue light. Auxin Response Factor is function as transcriptional regulators whose

activity is inhibited by binding to proteins under low light conditions such as red light or

ethylene also promote phototropism by controlling the expression of genes containing

auxin response elements. Eight genes with differential transcript accumulation across

phototropic-stimulated involved in cell wall extension. Auxins are compounds that

positively influence cell enlargement, bud formation and root initiation. They also

promote the production of other hormones and in conjunction with cytokinins, they

control the growth of stems, roots, flowers and fruits. Auxins were the first class of

growth regulators discovered. They affect cell elongation by altering cell wall plasticity.

Auxins decrease in light and increase were its dark. More auxin flows down the dark

side, meaning that it grows faster than the exposed side of the plant. This unequal or one-

sided growth (also called differential growth) cause bending of the plant toward the light

source. The interaction of plants hormones and photoreceptors contributes to plant

development.The genes encoding for AUX/IAA proteins also contain this AuxRE, a

negative feedback loop involving the up regulation of AUX/IAA proteins may participate

in the progression of normal phototropism.

UNIVERSITI PENDIDIKAN SULTAN IDRIS TANJUNG MALIM, PERAK

PLANT PHISIOLOGY

TBF3023

[Phototropism: Bending towards Enlightenment]

NAMA: MUHAMAMD SHAKIR BIN CHE SOH

NO MATRIK: D20081032384

NO IC: 890205-02-5269

PROGRAM: PENDIDIKAN SAINS (BIOLOGI)

KUMPULAN: B

NAMA PENSYARAH: DR HASIMAH ALIMON