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Influence of Phosphorus and Potassium on Alfalfa Yield, Taproot C and N Pools, and Transcript Levels of Key Genes after Defoliation
Author(s) -
Berg W. K.,
Cunningham S. M.,
Brouder S. M.,
Joern B. C.,
Johnson K. D.,
Volenec J. J.
Publication year - 2009
Publication title -
crop science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.76
H-Index - 147
eISSN - 1435-0653
pISSN - 0011-183X
DOI - 10.2135/cropsci2008.07.0395
Subject(s) - taproot , biology , medicago sativa , sucrose phosphate synthase , shoot , agronomy , nutrient , phosphorus , zoology , sowing , sucrose synthase , botany , sucrose , horticulture , chemistry , biochemistry , invertase , ecology , organic chemistry
Fertilization with K and P impacts alfalfa ( Medicago sativa L.) yield, but how these nutrients influence taproot reserves and gene expression is unknown. Our objectives were to determine how P and K impact (i) alfalfa yield and yield components, (ii) accumulation and use of taproot carbon (C) and nitrogen (N) pools, and (iii) transcript levels for β‐amylase, sucrose synthase, and the high molecular weight vegetative storage protein in alfalfa taproots. Yield and yield components were determined at 30‐d intervals beginning in late May. Roots were sampled after the late June harvest (Day 0) and 1, 3, 6, 10, 14, 21, and 30 d thereafter. Addition of P and K increased forage yield by enhancing mass per shoot. High P resulted in rapid starch use, while taproots of plants fertilized with K had low sugar concentrations. Transcripts decline by Day 6 and by Day 10 were below detection limits. Transcripts for β‐amylase and sucrose synthase accumulated rapidly after Day 10 in taproots of plants fertilized with both P and K. Balanced P and K nutrition resulted in the accumulation and effective utilization of C and N reserves and in improved alfalfa adaptation to defoliation.