Plant Stress (Jun 2024)
Citrullus colocynthis regulates photosynthetic and biochemical processes to develop stress resilience and sustain growth under sub-optimal temperatures
Abstract
Sub-optimal temperatures posed significant challenges to leaf photosynthesis and plant growth. This study examined the eco-physiological adaptations of a desert vine (Citrullus colocynthis) to unfavorable temperatures (15/25 °C, 25/35 °C, and 35/45 °C) over 35 days. Plants grown in moderate temperatures increased shoot number and leaf canopy (55 %), chlorophyll a (2.5 folds), and carotenoid accumulation compared to other treatments. Conversely, high-temperature stress resulted in longer shoot development with fewer primary branches, while low temperatures constrained both shoot and leaf growth. Plants treated with high heat exposure produced more oxidative stress markers (MDA and H2O2, by two folds), causing greater cellular damage while attaining lesser growth. During the high-temperature episode, plants increased their antioxidant enzyme activities and proline (2.5-fold) levels to protect the tissues from oxidative damage. Plants treated with either moderate or higher heat stress increased the potential quantum yield of photosystem II (Fv/Fm) and maximum quantum yield ФPSII in the young leaves, which indicated the constitutive plant adaptation to unfavorable temperatures. Additionally, photosynthetic efficiency differed with leaf age and temperature; mature leaves performed better physiologically at low temperatures, whereas young leaves adapted better at high temperatures stress. The results suggested that C. colocynthis plants were highly adaptable to unfavorable temperatures by regulating the plants’ thermal homeostatic ability through their photosynthetic and biochemical processes. This study provided deeper insights into species-specific eco-physiological responses to sub-optimal temperatures and contributed to our broader understanding of plant resilience and ecological adaptability in the era of global climate change.
