Submitted to: Biomed Central (BMC) Plant Biology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/16/2008
Publication Date: 12/16/2008
Citation: Niedz, R.P., Evens, T.J. 2008. The effects of nitrogen and potassium nutrition on the growth of nonembryogenic and embryogenic tissue of sweet orange (Citrus sinensis (L.) Osbeck). Biomed Central (BMC) Plant Biology. 8:126. doi:10.1186/1471-2229-8-126 Interpretive Summary: The healthy and vigorous growth of plant cells and tissues in the laboratory is a prerequisite to using those cells/tissues for various plant breeding applications such as cell selection and genetic engineering. One of the most fundamental requirements for growing plants is that the fertilizer used contains the appropriate types and quantities of mineral nutrients. This is true for all plants grown under all conditions (e.g., field, greenhouse, hydroponic, and in vitro culture). When plants are supplied with the appropriate mineral nutrients, the result is healthy and vigorous growth. This study both reports and demonstrates the importance of appropriate mineral nutrition on the in vitro laboratory growth of two different sweet orange tissue cultures commonly used in citrus plant improvement programs – embryogenic tissue and nonembryogenic tissue. Tissue growth of both sweet orange tissue types was increased by the defining the appropriate level of three essential plant nutrients – ammonium, potassium, and nitrate. Nonembryogenic tissue growth was increased from the control 330% increase in tissue mass over 14 days to 905%. Embryogenic tissue growth was increased from 305% to 505%.
Technical Abstract: The objective of this study was to improve the growth of sweet orange (Citrus sinensis (L.) Osbeck cv. ‘Valencia’) nonembryogenic and embryogenic callus tissue via nitrogen nutrition. The experimental approach was a mixture-amount design comprised of a two-component NH4+:K+ mixture that ranged from 0:1 to 0.5:0.5 and NO3- amount that ranged from 10 mM to 50 mM. The amount of NH4+ + K+ was matched to the amount of NO3-. The specific treatment points were selected by D-optimality criteria to sample the two-dimensional design space. A linear programming algorithm was used to calculate the salts/acids/bases required to make each formulation where all inorganic ions other than the three ions being varied were fixed at their MS levels. This resulted in a design and a set of media formulations free of ion confounding and thus allowed a direct determination of the ion-specific effects of NH4+, K+, and NO3- on the growth of the two selected citrus tissue types. Fresh weight growth for nonembryogenic tissue was increased from 330% for the control MS-based medium to 905%, and from 302% to 505% for embryogenic tissue. The dominant driver of these responses was the NH4+:K+ ratio.