
TY  - JOUR
A1  - Noquet, Carine 
A1  - Meuriot, Frédéric 
A1  - Caillot, Sébastien 
A1  - Avice, Jean-Christophe 
A1  - Ourry, Alain 
A1  - Cunningham, Suzanne M. 
A1  - Volenec, Jeffrey J. 
T1  - Short-day photoperiod induces changes in N uptake, N partitioning and accumulation of vegetative storage proteins in two <emph type="2">Medicago</emph> <emph type="2">sativa</emph> cultivars
JF  - Functional Plant Biology
JO  - Functional Plant Biol.
Y1  - 2003
VL  - 30
IS  - 8
SP  - 853
EP  - 863
KW  - Medicago sativa, N partitioning, N reserves, phytochrome, regulation, short day, VSP accumulation.
UR  - https://doi.org/10.1071/FP03099 
N2  - Our objective was to study the effect of short-day photoperiod for 28, 42 and 56 d on growth, N uptake and N partitioning, particularly vegetative storage protein (VSP) accumulation in taproots of two alfalfa (Medicago sativa L.) cultivars (Lodi and Europe). For both varieties, the reduction of daylength from 16 h (long day, LD) to 8 h (short day, SD) for 28 d reduced total plant growth by decreasing shoot growth. Nitrogen uptake and N distribution within the plant was determined by 15N labeling. N uptake decreased with SD treatment duration, and was 2- and 3-fold lower for Europe and Lodi, respectively, for 56 d in SD conditions when compared with LD plants. The SD treatment resulted in preferential partitioning of N to taproots in comparison with LD conditions (19 vs 9% for Lodi and 12 vs 5% for Europe after 28 d). For both cultivars, the SD-induced changes in N allocation to taproots did not significantly affect taproot soluble protein concentrations during 42 d of daylength treatment. In contrast, VSP accumulation occurred after only 28 d for plants grown in SD conditions (6.2 vs 4.8 mg g&#8211;1 DW for Lodi and 5.1 vs 1.4 mg g&#8211;1 DW for Europe). SD exposure also increased vsp 57 and vsp 32 mRNA transcript levels in Lodi and Europe (up to 2-fold higher) taproots in SD for 28 d compared with LD conditions. Overall results indicate that photoperiod modulates taproot N accumulation in alfalfa by enhancing both &#946;-amylase (vsp 57) and vsp 32 gene expression and accumulation. The enhanced VSP accumulation by short-day photoperiod may result from altered VSP gene expression / transcript stability or occur indirectly through altered N source&#8211;sink relationships. Additionally, when SD treatment included a night break with 15 min illumination with sodium high pressure light or red light, our results suggest that the induction of vsp 57 and vsp 32 gene expressions by SD signal is mediated by the phytochrome system. 
ER  -

