Physiology of Nitrogen and Calcium Nutrition in Blueberry (Vaccinium sp.)

Sustaining the fourfold increase in blueberry (Vaccinium sp.) production witnessed during the previous two decades requires better understanding of its mineral nutrient physiology. The primary goals of this review are to evaluate our current understanding of the physiology of nitrogen (N) and calcium (Ca) nutrition in blueberry. Nitrogen concentration in blueberry ranges from 0.4% to >2% across organs. Blueberry uses N in various forms (organic and inorganic), but it appears to display preference for ammonium (NH4+) over nitrate (NO3−). The roles of N acquisition, translocation and assimilation in determining N-source preference in blueberry are evaluated. Calcium plays important roles in determining fruit quality owing to its function in maintaining cell wall and membrane integrity. It is unique in its translocation characteristics being transported primarily via the xylem. Fruit [Ca2+] typically declines from around 0.2% during early development to <0.05% at ripening. Modes of Ca acquisition and transport to the fruit, and various approaches to improve fruit [Ca2+] are discussed. Areas where further research is warranted to improve our understanding of N and Ca physiology in blueberry are identified. Such knowledge is essential for sustainable nutrient management, improving productivity, and enhancing fruit quality in blueberry.

Carbon and nutrient physiology in shrubs at the upper limits: a multi-species study

Aims Carbon and nutrient physiology of trees at their upper limits have been extensively studied, but those of shrubs at their upper limits have received much less attention. The aim of this study is to examine the general patterns of non-structural carbohydrates (NSCs), nitrogen (N) and phosphorous (P) in shrubs at the upper limits, and to assess whether such patterns are similar to those in trees at the upper limits. Methods Across Eurasia, we measured the concentrations of soluble sugars, starch, total NSCs, N and P in leaves, branches and fine roots (&lt; 0.5 cm in diameter) of five shrub species growing at both the upper limits and lower elevations in both summer (peak growing season) and winter (dormancy season). Important Findings Neither elevation nor season had significant effects on tissue N and P concentrations, except for lower P concentrations in fine roots in winter than in summer. Total NSCs and soluble sugars in branches were significantly higher in winter than in summer. There were significant interactive effects between elevation and season for total NSCs, starch, soluble sugars and the ratio of soluble sugar to starch in fine roots, showing lower soluble sugars and starch in fine roots at the upper limits than at the lower elevations in winter but not in summer. These results suggest that the carbon physiology of roots in winter may play an important role in determining the upward distribution of shrubs, like that in the alpine tree-line trees.