Differential freezing resistance and photoprotection in C3 and C4 eudicots and grasses

Abstract

Globally, C4 plants dominate hot, open environments, but this general pattern is underpinned by important differences in the biogeography of C4 lineages. In particular, the species richness of C4 Poaceae (grasses) increases strongly with increasing temperature, whereas that of the major C4 eudicot group Chenopodiaceae correlates positively with aridity. Freezing tolerance is a crucial determinant of biogeographical relationships with temperature and is mediated by photodamage and cellular disruption by desiccation, but little is known about differences between C4 families. This study hypothesized that there is a greater risk of freezing damage via these mechanisms in C4 Poaceae than Chenopodiaceae, that freezing protection differs between the taxonomic groups, and that freezing tolerance of species is linked to arid habitat preference. Chlorophyll fluorescence, water relations, and freezing injury were compared in four C3 and six C4 species of Poaceae and Chenopodiaceae from the same Mongolian flora. Contrary to expectations, freezing-induced leaf mortality and photodamage were lower in Poaceae than Chenopodiaceae species, and unrelated to photosynthetic pathway. The freezing resistance of Poaceae species resulted from constitutive protection and cold acclimation and an ability to protect the photosynthetic apparatus from photodamage. Freezing protection was associated with low osmotic potential and low tissue elasticity, and freezing damage was accompanied by electrolyte leakage, consistent with cell-membrane disruption by ice. Both Chenopodiaceae and Poaceae had the potential to develop cold acclimation and withstand freezing during the growing season, which conflicted with the hypothesis. Instead, freezing tolerance was more closely associated with life history and ecological preference in these Mongolian species.

Macro-Climatic Distribution Limits Show Both Niche Expansion and Niche Specialization among C4 Panicoids

“…At present, the climate data set suggests that C 3 panicoids are not more successful than their C 4 relatives in cold climates and that more C 4 than C 3 panicoid lineages have reached cold regions. This is in agreement with recent ecophysiological studies that suggest C 4 species have no intrinsic barrier to developing freezing tolerance, and that in some ecosystems the chance of developing freezing resistance may depend more on the capacity for drought resistance than on photosynthetic pathway [ 64 , 65 ].…”

The evolutionary ecology of C4plants

“…prairie grasses), in both cases overwintering in a dormant state, which is a common strategy adopted by plants to avoid episodic freezing (Zanne et al ., ). However, there seems to be no intrinsic barrier to freezing tolerance in a C 4 leaf, with species developing protection via constitutive or facultative cold acclimation mechanisms (Sage & Sage, ; Liu & Osborne, , ). The leaves of other C 4 species are intolerant of freezing, but have physiological mechanisms for protection against light‐mediated damage during chilling events in the range 0–10°C (Long, ; Naidu et al ., ).…”

Physiological Characteristics of <i>Medicago sativa</i> Seedlings in Response to Lab Simulated Basic Salt and Freeze-Thaw Stress

“…For example, low temperature stress can affect the cell membrane system, and then causes a series of physiological and biochemical changes such as varieties of proline [25]. Similarly, freezing leads to excessive water loss and causes proteins denaturation as well [26]. Beyond that, the effects of combined stress on proline and soluble protein were obviously enhanced in T4.…”