The influence of N and P supply and genotype on N remobilization in containerized Pinus radiata plants

Abstract

H.E. Bown, M.S. Watt, P.W. Clinton, and E.G. Mason. 2012. The influence of N and P supply and genotype on N remobilization in containerized Pinus radiata plants. Cien. Inv. Agr. 39(3): 505-520. A large proportion of the nitrogen (N) used in the current-year growth of the widely grown plantation species Pinus radiata D. Don is N that was stored in plant tissues the previous year. However, the extent to which an imbalance between levels of phosphorus (P) and N may change the capacity of plants to remobilize N is unknown. In this study, the N remobilization responses of four P. radiata genotypes to a factorial combination of N and P additions were assessed in containerized plants in a two-year greenhouse experiment. N supply was enriched with Sixty-five percent of the plant N content at the end of the first year of growth was remobilized during the second year in the high-N high-P supply treatment, compared to 42-48% for the other N and P addition treatments. The ratio of N uptake to N remobilization was greater for the high-N supply regimes compared to the low-N supply regimes, suggesting that trees may rely progressively more on remobilization than uptake as N fertility declines. Most N remobilization (77%) occurred during the spring-summer periods and coincided with the largest proportion of needle development (80%), suggesting that N remobilization was driven by sink-strength. Old foliage was the main source for internal cycling, while roots were the main sink. Faster-growing genotypes did not exhibit an enhanced capacity for N remobilization, suggesting that genetically induced growth performance is not explained by N internal cycling. In conclusion, trees growing with an abundant and balanced nutrient supply exhibited greater capacity for nitrogen remobilization than trees with N and/or P deficiencies however, faster-growing clones did not exhibit an enhanced capacity for N remobilization.

Growth and nutrient efficiency of Betula alnoides clones in response to phosphorus supply

“…The allocation of more resources to the root, so as to absorb more water and nutrients to support plant growth, helps to explain the greater productivity in this clone ). This can also be confirmed from its higher nutrient absorption efficiencies and NUE (Bown et al 2012;Folk & Grossnickle 2000). Clone BY1 had lower leaf nitrogen concentration but higher leaf potassium concentration compared with other clones, suggesting that nitrogen dilution and synergism between phosphorus and potassium ions were occurred in the fast-growing clones of B. alnoides.…”

“…The survival and early performance of outplanted nursery stock at the establishment stage are likely to be more influenced by internal nutrient retranslocation than by the current nutrient supply, hence the benefit of nutrient loading in nursery production (Bown et al 2012, Folk & Grossnickle 2000, Salifu & Timmer 2003 branches. This implies that the P4 treatment (70 mg P plant -1 ) was sufficient for the growth of B. alnoides clones.…”

Seasonal dynamics of nitrogen level and gas exchange in different cohorts of Scots pine needles: a conflict between nitrogen mobilization and photosynthesis?

“…Whether the influence of internal N mobilization on photosynthesis should be stronger at more oligotrophic sites, is debatable. On the one hand, the findings that N resorption efficiency from senescing leaves is negatively related to green leaf N concentration (Vergutz et al 2012) and that it is reduced by fertilization (Yuan and Chen 2015) suggest that the relative degree of reserve mobilization should also be higher in N-deficient plants (Bown et al 2012). On the other hand, mobilization of stored N is thought to be independent of current N supply and is mostly controlled by sink strength (Millard and Grelet 2010).…”