C4 photosynthesis boosts growth by altering physiology, allocation and size.

C4 photosynthesis is a complex set of leaf anatomical and biochemical adaptations that have evolved more than 60 times to boost carbon uptake compared with the ancestral C3 photosynthetic type(1-3). Although C4 photosynthesis has the potential to drive faster growth rates(4,5), experiments directly comparing C3 and C4 plants have not shown consistent effects(1,6,7). This is problematic because differential growth is a crucial element of ecological theory(8,9) explaining C4 savannah responses to global change(10,11), and research to increase C3 crop productivity by introducing C4 photosynthesis(12). Here, we resolve this long-standing issue by comparing growth across 382 grass species, accounting for ecological diversity and evolutionary history. C4 photosynthesis causes a 19-88% daily growth enhancement. Unexpectedly, during the critical seedling establishment stage, this enhancement is driven largely by a high ratio of leaf area to mass, rather than fast growth per unit leaf area. C4 leaves have less dense tissues, allowing more leaves to be produced for the same carbon cost. Consequently, C4 plants invest more in roots than C3 species. Our data demonstrate a general suite of functional trait divergences between C3 and C4 species, which simultaneously drive faster growth and greater investment in water and nutrient acquisition, with important ecological and agronomic implications

A marine biogenic source of atmospheric ice nucleating particles

The amount of ice present in clouds can affect cloud lifetime, precipitation and radiative properties1,2. The formation of ice in clouds is facilitated by the presence of airborne ice nucleating particles1,2. Sea spray is one of the major global sources of atmospheric particles, but it is unclear to what extent these particles are capable of nucleating ice3-11. Sea spray aerosol contains large amounts of organic material that is ejected into the atmosphere during bubble bursting at the organically enriched sea-air interface or sea surface microlayer12-19. Here we show that organic material in the sea surface microlayer nucleates ice under conditions relevant for mixed-phase cloud and high-altitude ice cloud formation. The ice nucleating material is likely biogenic and less than ~0.2 μm in size. We find that exudates separated from cells of the marine diatom T. Pseudonana nucleate ice and propose that organic material associated with phytoplankton cell exudates is a likely candidate for the observed ice nucleating ability of the microlayer samples. Global model simulations of marine organic aerosol in combination with our measurements suggest that marine organic material may be an important source of ice nucleating particles in remote marine environments such as the Southern Ocean, North Pacific and North Atlantic

Effects of chlorinated benzenes on diatom fatty acid composition and quantitative morphology. I. 1,2,4-Trichlorobenzene

Cells of the diatom Cyclotella meneghiniana were exposed in a closed system to 0.245 ppm 1,2,4-trichlorobenzene. Response to this chlorinated benzene was monitored over a period of 5 days by quantitative ultrastructure and fatty acid percent composition. Over the time period examined, 41 significant morphological changes and 12 significant changes in fatty acid composition were observed. Autophagic-like vacuoles were frequently observed, indicating lysis of cellular constituents. In general, there was an increase in the C20:5 fatty acid, which may be indicative of photosynthetic impairment, since this fatty acid probably substitutes for linolenic acid in diatoms. The most significant numbers of changes were observed after 8 hr of exposure to this lipophilic toxicant, and these changes occurred in membranous organelles. It is suggested that the daily photoperiodic variation in lipid content of phytoplankton may be an important consideration in evaluating effects of lipohilic toxicants.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/48069/1/244_2005_Article_BF01225001.pd

A coastal coccolithophore maintains pH homeostasis and switches carbon sources in response to ocean acidification

WOS:000439301700001International audienceOcean acidification will potentially inhibit calcification by marine organisms; however, the response of the most prolific ocean calcifiers, coccolithophores, to this perturbation remains under characterized. Here we report novel chemical constraints on the response of the widespread coccolithophore species Ochrosphaera neapolitana (O. neapolitana) to changing-CO2 conditions. We cultured this algae under three pCO(2)-controlled seawater pH conditions (8.05, 8.22, and 8.33). Boron isotopes within the algae's extracellular calcite plates show that this species maintains a constant pH at the calcification site, regardless of CO2-induced changes in pH of the surrounding seawater. Carbon and oxygen isotopes in the algae's calcite plates and carbon isotopes in the algae's organic matter suggest that O. neapolitana utilize carbon from a single internal dissolved inorganic carbon (DIC) pool for both calcification and photosynthesis, and that a greater proportion of dissolved CO2 relative to HCO3- enters the internal DIC pool under acidified conditions. These two observations may explain how O. neapolitana continues calcifying and photosynthesizing at a constant rate under different atmospheric-pCO(2) conditions