Some seeds remain alive underground for years before conditions allow them to grow. Their ou coverings pro the liv tissues fr damage wh chemical sig prevent ea growth un suitable condi finally arr. This delay can help a plant population survive a season when rain is scarce. Not all seeds respond to the same signals: some require a period of cold, whereas others begin growing after exposure to light. A patch of apparently bare ground may therefore contain a reserve of future plants.

Type only the missing letters. Each box is one letter, and the number of boxes matches the letters that are missing.