Importance of natural cloud regimes to ecophysiology in the alpine species, Caltha leptosepala and Arnica parryi, Snowy Range Mountains, southeast Wyoming, USA.

The south-central Rocky Mountains, USA, are characterised by a dry, continental mesoclimate with typical convective cloud formation during the afternoon. Little is known about the specific influence of such predictable cloud patterns on the microclimate and ecophysiology of associated species. During the summer of 2012, days with afternoon clouds were most common (50% of all days) compared with completely clear (24%) or cloudy days (6.

Support for a photoprotective function of winter leaf reddening in nitrogen-deficient individuals of Lonicera japonica.

Plants growing in high-light environments during winter often exhibit leaf reddening due to synthesis of anthocyanin pigments, which are thought to alleviate photooxidative stress associated with low-temperature photoinhibition through light attenuation and/or antioxidant activity. Seasonal high-light stress can be further exacerbated by a limited photosynthetic capacity, such as nitrogen-deficiency. In the present study, we test the following hypotheses using three populations of the semi-evergreen vine Lonicera japonica: (1) nitrogen deficiency corresponds with reduced photosynthetic capacity; (2) individuals with reduced photosynthetic capacity synthesize anthocyanin pigments in leaves during winter; and (3) anthocyanin pigments help alleviate high-light stress by attenuating green light.

Photosynthetic costs and benefits of abaxial versus adaxial anthocyanins in Colocasia esculenta 'Mojito'.

Anthocyanins in upper (adaxial) leaf tissues provide greater photoprotection than in lower (abaxial) tissues, but also predispose tissues to increased shade acclimation and, consequently, reduced photosynthetic capacity. Abaxial anthocyanins may be a compromise between these costs/benefits. Plants adapted to shaded understory environments often exhibit red/purple anthocyanin pigmentation in lower (abaxial) leaf surfaces, but rarely in upper (adaxial) surfaces.

Estimating contribution of anthocyanin pigments to osmotic adjustment during winter leaf reddening.

The association between plant water stress and synthesis of red, anthocyanin pigments in leaves has led some plant biologists to propose an osmotic function of leaf reddening. According to this hypothesis, anthocyanins function as a solute in osmotic adjustment (OA), contributing to depression of osmotic potential (Ψ(π)) and maintenance of turgor pressure during drought-stressed conditions. Here we calculate the percent contribution of anthocyanin to leaf Ψ(π) during OA in two angiosperm evergreen species, Galax urceolata and Gaultheria procumbens.

Red leaf margins indicate increased polygodial content and function as visual signals to reduce herbivory in Pseudowintera colorata.

Red-pigmented leaf margins are common, but their functional significance is unknown. We hypothesized that red leaf margins reduce leaf herbivory by signalling to herbivorous insects the presence of increased chemical defences. Leaves were collected from a natural population of Pseudowintera colorata.