2023-10-03-BIOL254-W12-Notes .docx

LECTURE 5: PRINCIPLES OF PLANT PHYSIOLOGY Lecturer: Dr Claudia Meisrimler Take home message from Lecture notes. Auxins Auxin is a growth promoter. Auxins are associated with cell elongation and promoting the position of the vascular bundle. Cell identity is strongly associated with auxin. Auxin help...

LECTURE 5: PRINCIPLES OF PLANT PHYSIOLOGY Lecturer: Dr Claudia Meisrimler Take home message from Lecture notes. Auxins Auxin is a growth promoter. Auxins are associated with cell elongation and promoting the position of the vascular bundle. Cell identity is strongly associated with auxin. Auxin helps in maintaining stem cells populations. It is involved in leaf and lateral roots initiation. Auxin is involved with identity and initiation of the cells. Auxin uses the tryptophan pathway. The main type of auxin is indole acetic acid (IAA), the main auxin you find when analysing auxin in plants. In the roots auxin has an inhibiting function. Higher auxin will reduce elongation, low concentration will increase elongation while in the shoot, it is the opposite. Transport controls the concentration of auxins in the cells. Auxins uses receptors, Tir 1 and it is not a membrane associated receptor but an intracellular receptor. Tir1 binds to aux/IAA proteins. The Auxin Signalling Pathway (Usually asked in exams) Auxin binds to the SCF and Aux/IAA Aux/IAA ubiquitinated and degraded by 26S proteasome. Degradation of repressor permits transcriptional activation by ARF transcription factors. Cytokinins The structure one 1 cytokinin is called trans-zeatin. It also occurs in humans also and often associated with inflammation and in plants it is associated with cell division. It controls leaf senescence. Control of nutrient allocation. Root nodule development. Stem cell maintenance and regulation of auxin action because of the cross talk of cytokinins and auxin. Family of cytokinins are related to adenine-like compounds. Adenine pathway is the basis for cytokinins production.