To investigate the effects of atmospheric CO2 enrichment on physiology and autumnal leaf phenology, we exposed 3-year-old sugar maple (Acer saccharum Marsh.) seedlings to 800 (A8), 600 (A6), and 400 μL(CO2) L-1 (AA) in nine continuous stirred tank reactor (CSTR) chambers during the growing season of 2014. Leaf abscission timing, abscised leaf area percentages, leaf number, light-saturated net photosynthetic rate (PNmax), leaf area, accumulative growth rates, and biomass were determined and assessed. The results suggested the following: (1) no significant differences were found in the timing of leaf abscission in the three CO2-concentration treatments; (2) PNmax was continuously stimulated to the greatest extent in A8 at 319% and 160% in A6 until the end of the growing season, respectively; and (3) leaf number, leaf area, and accumulative height growth all significantly increased by elevated CO2, which led to a 323% increase in A8 biomass and 235% in A6 biomass after 156-d fumigation. In summary, the results suggest, the timing of leaf abscission of sugar maple in fall was not modified by CO2 enrichment, the increased carbon gain by elevated CO2 was mainly due to increased leaf area, more leaves, and the continuously enhanced high photosynthesis throughout the growing season instead of the leaf life span., L. Li, W. J. Manning, X. K. Wang., and Obsahuje bibliografii
The effects of awn removal on ear gas exchange in four barley lines (Morex, Harrington, Steptoe, and TR306) were studied under a controlled environment using a Before-After Control-Impact Paired (BACIP) experimental design. From ear emergence to grain maturity, plants were grown in pots at either 60 or 90 % of soil water holding capacity. Gas-exchange measurements of ears were made 9 and 10 d after anthesis (DAA). On 11 DAA, awn removal was performed on half of the ears in each pot, followed by measurements on both intact and de-awned ears on 12 and 13 DAA. Net photosynthetic (PN) and transpiration (E) rates decreased significantly with awn removal, but dark respiration (RD) rate was not affected. We estimated for each ear a temperature-adjusted respiration rate (Ra) from RD. When we corrected PN with Ra, we found that rates of spikelet photosynthesis were largely underestimated. Moderate water stress had minimal effect on gas exchange of bracts and awns of the barley ear. Barley lines did not differ for any individual gas-exchange parameter. and Q. Z. Jiang ... [et al.].