Phototropic Leaflet Reorientation in Alfalfa Germplasm Selected for Leaf Color and Size |
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Authors: | R L Travis R Reed |
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Institution: | University of California, Davis |
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Abstract: | Solar tracking has been described in several agronomic and wild species, yet variation within a given species has not been reported. To address that issue, photoperiod leaflet reorientation in response to vectorial light was measured in three alfalfa ( Medicago sativa L.) germplasm pools selected from the cultivar Ladak 65. Dark-leaf germplasm responded to all photosynthetic photon flux densities (PPFD) (100 to 700 μmol/m2/s) with no detectable lag period. Following a 24-h dark treatment only high PPFD (600 to 700μmol/m2/s) elicited reorientation. Pale-leaf germplasm responded to intermediate (300 to 400 μmol/m2/s) and high PPFD in a similar manner; however, the low (100-125μmol/m2/s) PPFD treatment had little effect on reorientation. The 24-h dark treatment decreased reorientation at all PPFD. Small-leaf germplasm responded equally to all PPFD and was not affected by the 24-h dark treatment. The results suggest that available energy levels may influence the reorientation response. Carbonyl cyanide m -chlorophenylhydrazone, an inhibitor of photophosphorylation, and 3-(3,4-dichlorophenyl)-1,1-dimethylurea, an inhibitor of non-cyclic photosynthetic electron transport, reduced reorientation only in the pale-leaf type. These results suggest that stored energy reserves were adequate to maintain leaflet reorientation in the absence of photosynthesis in all but the pale-leaf germplasm. In that germplasm photosynthetically generated energy may be required to support reorientation. |
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Keywords: | Medicago sativa L diaheliotropism solar tracking |
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