Auxin
Videos
Auxins are a class of plant hormones with some morphogen-like characteristics. Auxins play a cardinal role in coordination of many growth and behavioral processes in plant life cycles and are essentia
The auxin signal cascade: In the absence of auxin, Aux/IAA bind to and suppress the transcriptional activity of ARFs. When auxin is present it forms a 'molecular glue' between TIR1 and Aux/IAAs, which leads to the degradation of these repressors. ARFs are then free to bind to DNA and to cause changes in transcription.
Auxin diffuses along the shaded side of the plant, and causes cellulose in the cell wall to break, allowing turgor (water pressure) to expand the cell.
A healthy Arabidopsis thaliana plant (left) next to an auxin signal-transduction mutant with a repressed response to auxin.
Crown galls are caused by Agrobacterium tumefaciens bacteria; they produce and secrete auxin and cytokinin, which interfere with normal cell division and cause tumors.
Meristem
Videos
In cell biology, the meristem is a structure composed of specialized tissue found in plants, consisting of stem cells, known as meristematic cells, which are undifferentiated cells capable of continuo
Microscopic image of a shoot apical meristem surrounded by leaf primordia of Arabidopsis thaliana.
Note the long spur of the above flower. Spurs attract pollinators and confer pollinator specificity. (Flower: Linaria dalmatica)
Complex leaves of Cardamine hirsuta result from KNOX gene expression