Instant Notes: Plant Biology

Ahormoneis defined as a naturally occurring, organic substance that, at low concentration, exerts a profound influence on a phys ...

much more sensitive, with maximum stimulation of growth at 10–9–10–10M auxin, and inhibition at higher concentrations. Cell divi ...

fruits if they are treated with auxin. Senescence and abscission of mature leaves, fruits and flowers is inhibited by auxin; how ...

expressed in the root apex, which encodes an auxin transport protein which is involved in directional elongation, for instance i ...

Synthesis and degradation Ethylene is produced from the amino acid methionine, via S-adenosyl methio- nine(SAM) and 1-aminocyclo ...

Synthesis Gibberellins are diterpene acids synthesized by the terpenoid pathway. Terpenoids are compounds built of repeating iso ...

Cytokinin transport Cytokinins are synthesized in various tissues and organs, though the root apical meristem (Topic C2) is a ma ...

two stages to produce ABA. ABA is degraded, either by oxidation or by conju- gation, to form ABA-glucosyl ester. Abscisic acid t ...

Section F – Growth and development F3 Molecular action of hormones and intracellular messengers Plant hormones influence both lo ...

ways, with the same hormone having several different effects using several different mechanisms in the same plant, and even in t ...

Altered gene expression is an essential component of many hormone-regulated processes. Altered gene expression results in the pr ...

increased pumping of protons (H+) into the cell wall by the plasma membrane proton ATPase(proton pump; Topic I3). The acid growt ...

Table 2. Examples of auxin-responsive mRNAs Messenger RNAs identified Time taken to respond Notes that are up- or down-regulated ...

Calcium as an intracellular messenger Cells maintain a very low concentration of Ca2+in the cytoplasm (<1μM), by pumping it o ...

Plants also have a range of Ca2+-dependent(but calmodulin independent) protein kinases. Protein kinases are important in signal ...

Section G – Sensing and responding to the environment G1 Phytochrome, photoperiodism and photomorphogenesis Plants use light for ...

response to light; there are many other examples, including seed germination (some seeds will only germinate after being exposed ...

G1 – Phytochrome, photoperiodism and photomorphogenesis 85 O S A N Pro His Ser Cys His Leu Gln N N H H H 15 H B H 5 R R Pr 10 C ...

genes is not sensitive to light, and type II phytochrome is much less sensitive to proteolysis, so it remains more or less const ...

Section G – Sensing and responding to the environment G2 Tropisms Tropismsare responses to environmental stimuli which involve a ...