Development of chlorenchyma and window tissues in leaves of peperomia columella

Window leaves consist primarily of tissues specialized for water storage (window tissue) and photosynthesis (chlorenchyma). The objective of our research was to determine when these specializations occur during leaf development in Peperomia columella, a succulent window plant, native to deserts of South America. We measured absolute and relative volumes of leaf tissues. Young leaves consist of approximately 75% chlorenchyma and 12% window tissue, suggesting that they are structurally specialized primarily for photosynthesis rather than water storage. In mature leaves the percentages of chlorenchyma and window tissue are approximately 20% and 58%, respectively, indicating that specialization for water storage occurs during later stages of leaf development. The percent window tissue decreases in mature leaves, but increases in young leaves with water stress.