in a moment of understanding, he empathizes with Olan, understanding that she has worked hard and faithfully for him for many years without reward.  In this moment, the pearls symbolize Wang Lung's affection and admiration for Olan and her contributions.  The pearls are a visual symbol of his honest caring for his wife's happiness.

In later chapters, Wang Lung will take the pearls away from Olan to give to his mistress Lotus.  This offensive move not only reflects the transference of Wang's affections from Olan to Lotus, but also reveals Wang Lung's extremely selfish, thoughtless attitude.

For O-lan, the two pearls represent the only time in her life when she had something of her own. Most of O-lan's life has been devoted to hard work, raising the children, and catering to her husband's needs. The two pearls take on special significance because when Wang Lung gave them to O-lan, it was the only time he'd ever shown any appreciation toward her.

Over time they come to symbolize married love, a love that notably diminishes over the course of the marriage. Yet so long as O-lan can hang on to the pearls she will always be reminded of what was and what still might be. Such hopes are dashed, however, when Wang Lung cruelly takes the pearls away from O-lan and gives them to Lotus, thereby demonstrating once and for all that he longer loves her.