Caught in the light: The fulvalene diruthenium complex shown on the left side of the picture captures sun light, causing initial Ru-Ru bond rupture to furnish a long-lived triplet biradical of syn configuration. This species requires thermal activation to reach a crossing point (middle) into the singlet manifold on route to its thermal storage isomer on the right through the anti biradical.

Tonnage (T), Simmonds (S) avocado trees, and TxS crosses were evaluated for differences in chlorophyll content and maximal quantum yield of photosystem II in sun and shade-type leaves. Total chlorophyll content by area (Chl a+bar) ranged from 984 mg m in TxS240 to 4320 mg m in Simmonds. Chlorophyll a/b ratio (Chl a/b) ranged from 9.8 to 5.5 in TxS238 and TxS243, respectively. Tonnage and Simmon...

Light is an important resource for plant growth and development, crops need to change their physiological characteristics to different light environments. Fragaria ananassa Duch. cv. Toyonoka. is an important economic plant which is widely planted at home. A greenhouse experiment was conducted from April 2010 with different sun-shading treatment, 85% (CK), 60% (T1), 35% (T2) and 10% (T3). After...

Tree seedlings developing in the understory of the tropical forest have to endure short periods of high-light stress when tree-fall gaps are formed, and direct solar radiation, including substantial UV light, reaches the leaves. In experiments simulating the opening of a tree-fall gap, the response of photosynthesis in leaves of shade-acclimated seedlings (Anacardium excelsum, Virola surinamens...

The photosynthetic sensitivity to high light differs among understory plants of shade- and sun- established tree species. Shade-established tree species are sensitive to high light but the underlying photosynthetic mechanism has not been fully resolved. In the present study, we examined the responses of photosystem I (PSI) and photosystem II (PSII) to high light in shade leaves of a shade-estab...

Trifoliolate leaves of Crotalaria pallida Aiton (Fabaceae) exhibit sun-tracking behavior in simulated days and in response to a fixed, oblique light. The site of light perception for sun-tracking is on the lamina, necessitating transport of a signal from the lamina to the site of response (the pulvinule at the base of the leaflet). Evidence for the site of light perception on the lamina include...

Interacting effects of high light and drought on the performance of sun and shade phenotypes were experimentally undertaken following survival, chlorophyll fluorescence and gas exchange in 2-year-old saplings of four Mediterranean trees (Quercus ilex and Q. coccifera as water-saving species, and Pistacia lentiscus and P. terebinthus as water-spending species). Half of the saplings were grown in...

During winter, the light-harvesting complexes of evergreen plants change function from energy-harvesting to energy-dissipating centers. The goal of our study was to monitor changes in the composition of the photosynthetic apparatus that accompany these functional changes. Seasonal changes in chlorophyll fluorescence, pigment concentration, and abundance and phosphorylation status of photosynthe...

The circadian clock has a vital role in monarch butterfly (Danaus plexippus) migration by providing the timing component of time-compensated sun compass orientation, which contributes to navigation to the overwintering grounds. The location of circadian clock cells in monarch brain has been identified in the dorsolateral protocerebrum (pars lateralis); these cells express PERIOD, TIMELESS, and ...

Nanoflares have been proposed as the main source of heating of the solar corona. However, detecting them directly has so far proved elusive, and extrapolating to them from the properties of larger brightenings gives unreliable estimates of the power-law exponent α characterising their distribution. Here we take the approach of statistically modelling light curves representative of the quiet Sun...