Pollen tube are tolerant and even pollen damaged by X-rays and gamma rays can still grow pollen tubes. The interaction between the stigma-style and the pollen grain is a vital piece that contributes to the growth. The elongation of the tube is achieved with elongation of the cytoskeleton and it extends from the tip, which is regulated by high levels of calcium in the cytosol. The calcium levels help the synaptic vesicles in the membranes grow and extend at the tip. Polypeptides found in the style also regulate growth of tube and specific peptides that play a role in signaling for growth
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