Final answer:
Warm-season grasses turn brown and enter dormancy in response to colder temperatures and shorter days, conserving energy until favorable conditions return. This strategy is similar across many plants, including vineyards, where vines hibernate during winter.
Step-by-step explanation:
When warm-season grasses go dormant in the colder months, their color typically fades or turns brown. This dormancy is a survival strategy that allows the plant to conserve energy by switching to anaerobic metabolism and pausing growth until conditions are favorable again. As daylight decreases, the production of chlorophyll in leaves diminishes, leading to the loss of the usual green color and the emergence of other pigments, if present. While this is a common occurrence in many herbaceous plants, in grasses, the entire plant often appears brown and lifeless.
Similarly, vineyards experience dormancy during winter when the vines enter a state of hibernation to survive until spring. This biological phenomenon is triggered by environmental cues such as shorter day length and cooler temperatures. In this 'long nap,' they conserve resources and prepare for the burst of activity in spring when they break dormancy. Each year, plants respond to seasonal changes with various behaviors such as leaf color changes and flowering at different times.