Search

This year marks the 100th anniversary of the experiments by Garner and Allard that showed that plants measure the duration of the night and day (the photoperiod) to time flowering. This discovery led to the identification of Flowering Locus T (FT) in Arabidopsis and Heading Date 3a (Hd3a) in rice as a mobile signal that promotes flowering in tissues distal to the site of cue perception. FT/Hd3a belong to the family of phosphatidylethanolamine-binding proteins (PEBPs). Collectively, these proteins control plant developmental transitions and plant architecture. Several excellent recent reviews have focused on the roles of PEBPs in diverse plant species; here we will primarily highlight recent advances that enhance our understanding of the mechanism of action of PEBPs and discuss critical open questions. [ABSTRACT FROM AUTHOR]

Five-year-old Scots pine (Pinus sylvestrisL.) seedlings were grown in open-top chambers at ambient and elevated (ambient + 400 μmol mol−1) CO2 concentrations. Net photosynthesis (A), specific leaf area (SLA) and concentrations of nitrogen (N), carbon (C), soluble sugars, starch and chlorophyll were measured in current-year and 1-year-old needles during the second year of CO2 enrichment. The elevated CO2 treatment stimulated photosynthetic rates when measured at the growth CO2 concentration, but decreased photosynthetic capacity compared with the ambient CO2 treatment. Acclimation to elevated CO2 involved decreases in carboxylation efficiency and RuBP regeneration capacity. Compared with the ambient CO2 treatment, elevated CO2 reduced light-saturated photosynthesis (when measured at 350 μmol mol−1 in both treatments) by 18 and 23% (averaged over the growing season) in current-year and 1-year-old needles, respectively. We observed significant interactive effects of CO2 treatment, needle age and time during the growing season on photosynthesis. Large seasonal variations in photosynthetic parameters were attributed to changes in needle chemistry, needle structure and feedbacks governed by whole-plant growth dynamics. Down-regulation of photosynthesis was probably a result of reduced N concentration on an area basis, although a downward shift in the relationship between photosynthetic parameters and N was also observed. [ABSTRACT FROM PUBLISHER]