How does pollen tube malformation affect fertilization?

A pollen tube malformation occurs when the pollen tube fails to develop, grow properly, or reach the ovule. This can result from genetic defects, environmental stress (like high temperature or pollution), or improper nutrient or hormone balance within the style. 

Since the pollen tube is responsible for delivering male gametes to the ovule, any abnormality in its structure or direction directly affects fertilization. If the pollen tube grows too slowly, takes a wrong path, or bursts prematurely, the sperm cells may never reach the egg cell, preventing fertilization. This leads to reduced seed set or sterility in plants. 

Malformations can include swollen tips, branching tubes, or failure to penetrate the ovule. In some cases, incompatibility between pollen and stigma (self-incompatibility) can also trigger malformation. Research in plant reproduction shows that calcium ions, proteins, and signaling molecules are vital for proper tube growth. Therefore, any disruption in these signaling pathways can stop fertilization, affecting fruit and seed production — a key concern in agriculture and hybrid breeding.