[1] This study evaluates the potential impact of clouds on ecosystem CO2 and CO2 isotope fluxes (‘‘isofluxes’’) in two contrasting ecosystems (a broadleaf deciduous forest and a C4 grassland) in a region for which cloud cover, meteorological, and isotope data are available for driving the isotope-enabled land surface model (ISOLSM). Our model results indicate a large impact of clouds on ecosyst...

X y effort to understand the basis of life on this planet must always come back to photosynthesis: the process that enables plants to grow by utilizing carbon dioxide (C02), water (H20) and a tiny amount of minerals, Photosynthesis is the one large-scale process that converts simple, stable, in­ organic compounds into the energy-rich combination of organic matter and oxy­ gen and thereby makes ...

Rates of photosynthesis, sucrose synthesis, starch accumulation and degradation were measured in sugar beet (Beta vulgaris L.) and bean (Phaseolus vulgaris L.) plants under a square-wave light regime and under a sinusoidal regime that simulated the natural daylight period. Photosynthesis rate increased in a measured manner in direct proportion to the increasing light level. In contrast to this ...

UNLABELLED C4 photosynthesis is considered one of the most remarkable examples of evolutionary convergence in eukaryotes. However, it is unknown whether the evolution of C4 photosynthesis required the evolution of new genes. Genome-wide gene-tree species-tree reconciliation of seven monocot species that span two origins of C4 photosynthesis revealed that there was significant parallelism in the...

BACKGROUND AND AIMS Monsi and Saeki (1953) published the first mathematical model of canopy photosynthesis that was based on the light attenuation within a canopy and a light response of leaf photosynthesis. This paper reviews the evolution and development of their theory. SCOPE Monsi and Saeki showed that under full light conditions, canopy photosynthesis is maximized at a high leaf area ind...

How trees sense source-sink carbon balance remains unclear. One potential mechanism is a feedback from non-structural carbohydrates regulating photosynthesis and removing excess as waste respiration when the balance of photosynthesis against growth and metabolic activity changes. We tested this carbohydrate regulation of photosynthesis and respiration using branch girdling in four tree species ...

Profiles of N(2) fixation, O(2) production (gross photosynthesis), O(2) concentration, chlorophyll a concentration, and photon fluence rates were measured with 50-mum resolution in colonies of the heterocyst-forming cyanobacterium Nostoc parmelioides. Microelectrode measurements were made after 20 h of incubation under N(2) gas. Colonies were frozen, and 50-mum sections were prepared by using a...

At 14-hour day length, 25 C leaf temperature, 9 mm Hg vapor-pressure deficit, and 1.17 joules cm(-2) min(-1) irradiance, the diurnal change in daily photosynthesis of the cultivated peanut (Arachis hypogaea L.) is a result of an endogenously controlled circadian rhythm in net photosynthesis which peaks near noon and troughs near midnight. By resetting the day-night light regime, the rhythm reph...

C4 photosynthesis has independently evolved from the ancestral C3 pathway in at least 60 plant lineages, but, as with other complex traits, how it evolved is unclear. Here we show that the polyphyletic appearance of C4 photosynthesis is associated with diverse and flexible evolutionary paths that group into four major trajectories. We conducted a meta-analysis of 18 lineages containing species ...

The question then is how the same neurons convey two different sorts of information. The answer is that motor giants are capable of generating two types of action potentials, small/slow calcium spikes and large/fast sodium spikes, depending on the degree of depolarization it receives. As opposed to the input from the ring giant, the input from the pacemaker is too low to trigger the sodium spik...