Regulating Plant Tissue Growth by Mineral Nutrition.

Authors: Niedz, Randall; Evens, Terence

Submitted to: In Vitro Cellular and Developmental Biology - Plants
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/20/2007
Publication Date: 6/20/2007
Citation: Niedz, R.P., Evens, T.J. 2007. Regulating plant tissue growth by mineral nutrition. In Vitro Cellular and Developmental Biology - Plants. 43(4):370-381.

Interpretive Summary: The purpose of this study was to efficiently determine the appropriate mineral nutrients to regulate the growth of a sweet orange cell line. One of the primary problems in the cell and tissue culture of citrus, and many crop plants, is that for many important applications the in vitro responses are extremely poor. Developing useful applications are thus hampered due to the high cost associated with compensating for poor responses. For example, having to culture 1000 explants to only recover a dozen or less is costly. The problem of developing optimal nutrient levels is one of experimental complexity. There are sixteen mineral nutrients essential for plant growth. All possible combinations of these sixteen nutrients each at three levels – low, medium, and high, results in 43,046,721 treatment combinations. The experiments reported here utilized a geometric approach that only required 43 combinations. The result was that growth was predictably varied from 15% to over 140% of the growth on the control medium.

Technical Abstract: The objective of this study was to determine if the growth of sweet orange (Citrus sinensis (L.) Osbeck cv. ‘Valencia’) nonembryogenic callus could be regulated and controlled via the mineral nutrient components of the medium. The fourteen salts comprising MS basal medium were subdivided into five component groups. These five groups constituted the independent factors in the design. A five-dimensional hypervolume constituted the experimental design space. Design points were selected algorithmically by D-optimality criteria to sample of the design space. Growth of the callus at each design point was measured as % accumulation of fresh weight at 14 days. An ANOVA was conducted and a response surface polynomial model generated. Model validation was conducted by mining the polynomial for design points to two regions - “MS-like” growth and MS + 40% growth and comparing callus growth to predicted growth. Half of the eight selected MS-like points and one of the six MS + 40% growth points (point #22) validated indicating regions within the design space where growth was equivalent to MS but the salt combinations were substantially different from MS, and a smaller region where growth exceeded MS by over 40%. NH4NO3 and Fe were identified as important factors affecting callus growth. A second experiment was conducted where NH4NO3 and Fe were varied thus creating a 2-dimensional slice through the region of greatest callus growth, and provided increased resolution of the response.