Submitted to: Journal of Plant Nutrition
Publication Type: Peer reviewed journal
Publication Acceptance Date: 4/30/2010
Publication Date: 6/27/2012
Publication URL: handle.nal.usda.gov/10113/54300
Citation: Jaradat, A.A. 2012. Reproductive allocation and nutrient relationships in Cuphea: A semi-domesticated oilseed crop. Journal of Plant Nutrition. 35:1579-1599. Interpretive Summary: The loss of reproductive mass during plant growth and development represents a problem in understanding the allocation of dry matter to reproduction in Cuphea and could be attributed to nutrient imbalances. The relationships between a number of morphological traits and the carbon, nitrogen, and phosphorus concentrations in several plant tissues of Cuphea were analyzed at the vegetative and reproductive growth stages. The objectives were to predict how concentrations and ratios of these nutrients and the allocation of dry matter to stems, leaves and roots are interrelated, how they are influenced by growth stages and plant tissues, and how they impact the production of flowers, capsules and seeds. Changes in plant size due to branching and its transition from vegetative to reproductive growth phase resulted in changes in the concentrations of all three nutrients and their ratios in different plant parts and tissues. We found that the N:P ratios in leaves, flowers, capsules and seeds are almost stable throughout plant growth phases and are important in determining reproductive allocation in Cuphea. Large antagonistic effects of C:N on N:P ratios were found in different plant tissues, and suggest that maximum reproductive allocation can be attained by manipulating N:P ratio during plant growth and development. This information will help plant physiologists develop field-scale methods to alter growth and development so that plants can invest more nutrients and mass allocation for the benefit of reproductive biomass on the expense of stems and roots.
Technical Abstract: No information is available on allometric variations in C, N, and P in structural, reproductive and metabolic tissues and their ratios in Cuphea germplasm line PSR23, a semi-domesticated indeterminate and phenotypically plastic oilseed crop. The objectives of this study were to quantify the impact of ontogeny on allocation to reproductive mass and nutrient stoichiometry, and build and validate predictive and allometric models using dry matter allocation to stems, leaves, roots and reproductive organs, and nutrient stoichiometry as determinants of relative growth rate and net assimilation rate in Cuphea. Interrelationships between C, N, P; their ratios; and phenotypic traits estimated in structural, reproductive and metabolic tissues at vegetative and reproductive growth stages were used to derive and validate partial least square and reduced major axis regression models to study the interrelationships between ontogeny, allometric mass and nutrient ratios, and to predict relative growth rate and net assimilation rate as functions of growth stages, phenotypic traits and nutrient ratios in Cuphea. C, N, P, their ratios and stoichiometry were variable depending on growth stage and plant tissue. Ontogenically, N:P ratios in reproductive and metabolic tissues were least variable and were mainly affected by allometric leaf mass and relative growth rate. Reproductive mass is best predicted by allometric stem mass and C:N ratios in structural and metabolic tissues; whereas, net assimilation rate is best predicted by allometric total branch length and relative growth rate. The conservative N:P ratios in reproductive and metabolic tissues are important in determining reproductive allocation in Cuphea. The large variability in the observed PLS model exponents point to the large antagonistic effects of C:N on N:P ratios in different plant tissues, and suggests that maximum reproductive allocation can be attained by manipulating N:P ratio during ontogeny. A greater investment of resources in reproduction might be possible for this semi-domesticated crop if nutrient and mass allocation to supporting structures (i.e., roots and stems) can be altered for the benefit of reproductive biomass.