Relative growth and nutrient accumulation rates for tobacco

Summary Tobacco plants (Nicotiana tabacum L.) were grown from transplanting until floral expression in the phytotron units of Southeastern Plant Environment Laboratories to evaluate the relationship between relative growth rate (RGR) and relative accumulation rates (RAR) of N, P, K, Ca, and Mg. RAR is calculated to be analogous to RGR. Plants were grown in both controlled-environment rooms with artificial light and air-conditioned greenhouses with natural light at three temperature conditions and three application rates of N-P-K. RGR and RAR were calculated only for the period of grand growth which occurred within the interval from 7 to 32 days after transplanting. In general, neither RGR nor RAR were affected by temperature or nutrient level. However, both temperature and nutrient level affected dry matter accumulation of the plants apparently by an influence on the rapidity with which plants adjusted to their new environment during the initial 7-day interval after transplanting. RAR for P and K were coequal with RGR of the whole plant; thus, the concentrations of P and K within the plant tended to remain constant during growth. RAR for N, Ca, and Mg were less than RGR for the whole plant; thus, internal concentrations of these nutrients declined during growth. RAR of N, Ca, and Mg for the whole plant were equivalent to RGR of the roots. As a rationale for the association of RGR of roots and RAR of N, it is proposed that the soluble carbohydrate pool in the roots concurrently influences both N absorption, as NO₃ ^-, and growth of new roots of immature plants. Research reported in this paper was supported in part by National Science Foundation (RANN) Grants GI-39229 and GI-39230. Operation of the Phytotron Units of Southeastern Plant Environmental Laboratories at Duke and North Carolina State Universities was supported by National Science Foundation Grants GB-28950-1A and GI-28951. Approved as Paper Number 4773 of the Journal Series of the North Carolina Agricultural Experiment Station, Raleigh, NC. Research reported in this paper was supported in part by National Science Foundation (RANN) Grants GI-39229 and GI-39230. Operation of the Phytotron Units of Southeastern Plant Environmental Laboratories at Duke and North Carolina State Universities was supported by National Science Foundation Grants GB-28950-1A and GI-28951. Approved as Paper Number 4773 of the Journal Series of the North Carolina Agricultural Experiment Station, Raleigh, NC.