How Nonliving Factors Affect Cacti

Sunlight

• Because many cactus species prefer full sunlight locations, these species grow spines as shading mechanisms. For example, dense spines form shady areas on the cactus stems to regulate internal temperatures. When examined closely, you'll see that many spines have a white hue; light colors reflect sunlight and reduce heat stress. Cactus species with white hairs covering their stems have even more reflective power. Morning sunlight and dappled afternoon shade is a perfect growing location. If your cacti receive too much sunlight, their stems display a yellowed appearance; chlorophyll cells are dying back, losing their normal green hue. Heavily shaded cacti, in contrast, grow leggy as the plant reaches for potential sunlight.

Moisture

• Rainfall is infrequent and scarce where cacti thrive. In response, cacti spread their roots horizontally, rather than vertically, in search of moisture. Because their soil is mainly sand-based, water moves quickly through the grains; roots must be close to the surface to absorb as much moisture as possible. Water is stored within the cactus stems -- they visibly swell after a substantial rainfall. They use this stored water during drought. The spines also play a part in directing water to the roots. Dew forms on the spines and drips down onto the cactus roots. Rainfall is also funneled with spines to keep water near the roots for maximum uptake.

Photosynthesis

• With temperatures rising during summer days, cacti cannot photosynthesize like foliage plants. Photosynthesis involves transpiration, or water exchange, between plant cells and the surrounding air. In response to their extreme environment, cacti use Crassulacean Acid Metabolism (CAM) to transpire. For example, cacti open their stomata, or pores, along their stems during the night to absorb critical carbon dioxide. During the day, they use this stored gas molecule to photosynthesize while their stomata remain closed. As a result, cacti do not lose a lot of moisture during the day, especially since their stems are waxy and tough to prevent excessive evaporation.

Reproduction

• Most cacti create colorful blossoms, from yellow to red, to attract pollinators -- many species are self-pollinating but benefit from cross-pollination for genetic diversity. Each species blossoms at a different time to entice specific animals. Some cacti thrive in hot environments where pollinators only appear at night; these cacti produce night flowers for bats and other nocturnal organisms. Cacti living in more mild climates flower during the day for insect pollination. Nonliving factors, like local temperatures, affect flowering times and pollination, which cause plant adaptations for successful reproduction.