Dicot stem anomalous secondary growth occurs due to following reasons:

Anomalous position of cambium 

e.g.,Serjania sp. and Bauhinia sp.

Abnormal behavior of normal cambium

e.g., Bignonia, Aristolochia, Tinospora, Clematis etc.

Extrastelar cambium formation

e.g., Amaranthus sp. 

Interxylary phloem or included phloem

e.g., Entada sp (box bean), Combretum sp (Combretum), Strychnos sp.

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This combination of two positive feedback loops:

one that activates a CDK1 activator (Cdc25C)

one that inhibits a CDK1 inhibitor (Wee1)

results in the abrupt and irreversible transition from G2 into mitosis.

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In resting cells,

NF-κB binds directly to an inhibitor called I-κBα

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Tannins deter feeding by herbivores

Plant tannins also serve as defenses against microorganisms.

For example, the nonliving heartwood of many trees contains high concentrations of tannins that help prevent fungal and bacterial decay

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Homodimerization

HER1 directly binds EGF which leads to formation of a homodimer of the HER1 extracellular domain

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The size of a population is determined by a balance between births, immigration, deaths and emigration.