Axillary bud

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Plant Buds clasification.svg

The axillary bud is an embryonic shoot which lies at the junction of the stem and petiole of a plant.

As the apical meristem grows and forms leaves, it leaves behind a region of meristematic cells at the node between the stem and the leaf. These axillary buds are usually dormant, inhibited by auxin produced by the apical meristem, which is known as apical dominance. If the apical meristem was removed, or has grown a sufficient distance away from an axillary bud, the axillary bud may become activated (or more appropriately freed from hormone inhibition). Like the apical meristem, axillary buds can develop into a stem or flower.

Certain plant diseases - notably phytoplasmas - can cause the proliferation of axillary buds, and cause plants to become bushy in appearance.

Axillary buds can be used to differentiate if the plant is single-leafed or multi-leafed. Simply count the number of leaves after an axillary bud. If there is only one leaf, then the plant is considered single-leafed, vice versa.

During the formation of leaves and elongation of stem some cells are left behind from shoot apical meristem and constitute axillary bud


For a leaf which has the length of its midrib(i.e length from main axis of the plant to end point of leaf, mainly considered length of leaf) equal to L , and the angle of the leaf(angle made by the Petiole with the main axis of the plant) being θ, and the distance of the end point of the midrib from the main axis be R,

                              Sinθ = R/L ( By Trigonometry)

Let the length of axillary bud be l. the axillary bud can be considered a planar cyclic quadrilateral with its opposite angles being supplementary(i.e, θ and 180-θ). Assuming the width of the axillary bud to be an arc of length r, Sin(180-θ)≈ 180-θ can be written as

                              Sin(180-θ)= r/(l/2)=2r/l   ( angle=arc length /radius
      here arc length is r while radius is 1/2 the length of the axillary bud since it is considered inscribed in a circle)  
         by Trigonometric rules, Sin(180-θ)=Sinθ
                         i.e, R/L=2r/l
                        ⇒  l = 2 r L/R

If the plant is uniform , r≈1

                        ⇒  l = 2 L/R, which gives the length of an Axillary Bud.

This is Rohit Krishna's own contribution.