Cold Acclimation and Freezing Tolerance (A Complex Interaction of Light and Temperature)

Area of Science:

• Plant Physiology
• Molecular Biology
• Biochemistry

Background:

• Cold acclimation in winter rye (Secale cereale L. cv Musketeer) involves complex physiological and molecular adjustments.
• Photosystem II (PSII) plays a critical role in photosynthesis and is sensitive to environmental stresses like cold.
• Understanding the interplay between light, temperature, and PSII redox state is crucial for plant adaptation.

Purpose of the Study:

• To investigate the impact of varying temperature and irradiance on winter rye.
• To determine the influence of light, temperature, and PSII redox state on plant morphology, freezing tolerance, gene expression, and photosynthetic adjustment.
• To elucidate the specific roles of PSII redox state versus environmental factors in cold acclimation.

Main Methods:

• Winter rye was grown under five distinct temperature and irradiance regimes.
• Measurements included plant morphology, freezing tolerance (LT50), transcript levels (Lhcb, Wcs19, Wcs120), and photosynthetic parameters.
• Correlation analysis was used to link environmental factors and PSII redox state with observed plant responses.

Main Results:

• Cold-induced transcript Wcs19 accumulation, compact morphology, and enhanced non-photochemical quenching are linked to the PSII redox state, not solely growth conditions.
• Maximal freezing tolerance (LT50) and Lhcb/Wcs120 mRNA levels depend additively on both growth temperature and irradiance.
• Photosynthetic capacity and photoinhibition tolerance also adjusted in response to the tested regimes.

Conclusions:

• The relative reduction state of photosystem II is a key factor in specific cold acclimation responses, including Wcs19 expression and morphology.
• Maximal freezing tolerance acquisition is influenced by independent contributions of growth temperature and irradiance.
• Modulation of chloroplastic redox poise is likely important for photosynthetic acclimation and achieving maximal freezing tolerance.