Advances in research on the control of pollen tube growth by calcium in higher plants

Abstract

The function of the pollen tube in higher plants is to deliver two male gametes to the embryo sac to ensure successful double fertilization. During this process, many interactions occur among pollen tubes and pistil cells and tissues. Calcium ion (Ca^2 +) dynamics mediate these interactions to ensure that the pollen tube grows with correct polarity and orientation to reach its target, the embryo sac. The pistil tissue, which contains abundant Ca²⁺, attracts the growing pollen tube via changes in Ca²⁺. Recent studies have shed light on the mechanisms of vacuole biogenesis and the Ca²⁺ action pathway in the growing pollen tube. This successfully explains the distribution characteristics of high Ca²⁺ at the tip of the pollen tube and the physiological mechanism of Ca²⁺ controlling pollen tube growth. In last stage of pollen tube growth, some studies indicated that the cessation of pollen tube growth and breaking of the tube in embryo sac maybe related to Ca²⁺ dynamic, which finishes its complex journey of pollen tube in vivo.