Retranslocation of foliar nutrients of deciduous tree seedlings in different soil condition under free-air O3 enrichment

Abstract

Retranslocation is the amount of an element that is depleted from old plant components and is provided for new growth. Leaf senescence is usually accelerated at elevated O3 (eO3), and leaf shedding is influenced by soil nutrient availability (and acidification). In this study, we focused on the net retranslocation and allocation dynamics of foliar nutrients (N, P, Mg, K, Ca, Mn, Fe and Al) to investigate the effect of eO3 on birch (Betula platyphylla var. japonica), oak (Quercus mongolica var. crispula), and beech (Fagus crenata) seedlings grown in different soil conditions. Seedlings of the 3 species were planted in a free-air O3 enrichment system under 3 soil types (brown forest soil, serpentine soil, volcanic ash soil) for one growing season. All tree species were grown with 3 replications per each plot at elevated O3 (about 80 ppb) and ambient condition (O3 ranging 25-35 ppb). Leaf samples were taken from the top part of seedlings during the growing season in mid-September, and senescing leaves were sampled in mid-November. Both were collected for chemical composition analysis. Retranslocation rate of P was markedly increased by eO3 in birch and significantly differed among soil types in oak seedlings, while was constant across treatments in beech seedlings. Retranslocation of N in oak seedlings was significantly affected by soil type. Retranslocation of other elements was most sensitive to both eO3 and soil type in beech seedlings. The influence of differential growth patterns among species in modulating the physiological response of seedlings to high levels of ozone and different soil conditions are discussed.

Leaf stoichiometry of deciduous tree species in different soils exposed to free-air O 3 enrichment over two growing seasons

“…In order to fulfill the achievements, we investigated the stoichiometry issues from following aspects: 1) Effects of O3 or/and soil on foliar element contents in different species, and we expected that elements in oak leaves may have the least effects of O3 since oak is considered to be O3 tolerant in many previous studies (e.g. Kohno et al, 2005;Paoletti et al, 2007;Yamaguchi et al, 2011); 2) Effects of O3 or/and soil on foliar retranslocation rates, and we expected that mineral element retranslocation may be sensitive to the treatment in beech (Shi et al, 2016a); 3) Comparisons among species on elemental retranslocation rate during two growing seasons, and we expected that longterm exposure of eO3 has more adversely influence on foliar elements dynamics, especially for beech species; 4) Foliar elements contents and their relationships, and we expected that various highly correlations among foliar elements and also different contents of elements in leaves for each species may change the elements allocation dynamics and thereby affect the physiological and biochemical function in foliage; 5) Profiling the elements in different species by PCA analysis, and we expected to observe index elements that are able to assess the O3 and soil effects on these species.…”

“…There are big variations in sensitivity to O3 between various species grown in Japan. Among the 3 species, beech with determinate shoot growth pattern is more sensitive to O3 and its nutrient retranslocation is more efficient (Kohno et al, 2005;Shi et al 2016a). Oak is reported as a tolerant species with a highly capacity of O3 stress according to screening experiments of Kohno et al (2005) and Yamaguchi et al (2011).…”

“…Ecological stoichiometry deals with the balance of multiple elements in ecology interactions (Elser et al, 2000;Rong et al, 2015). Several studies have revealed that eO3 may have great impacts on foliar nutrient contents and can accelerate leaf senescence (Ribas et al, 2005;Hoshika et al, 2012b), resulting in an elemental imbalance in plants (Kam et al, 2015;Shi et al, 2016a). On one hand, a frequently observed effect of eO3 is a decline of N acquisition in plants, causes the nutrient deficiencies in leaves and thereby affects foliar physiological and biochemical functions (Karnosky et al, 2007;Yamaguchi et al, 2010).…”

“…On one hand, a frequently observed effect of eO3 is a decline of N acquisition in plants, causes the nutrient deficiencies in leaves and thereby affects foliar physiological and biochemical functions (Karnosky et al, 2007;Yamaguchi et al, 2010). Moreover, there were observations on the reduction of N, phosphorus (P) contents (Cao et al, 2016) and alternation on their allocations dynamics under eO3 treatment (Shi et al, 2016a). On the other hand, there were considerations suggested that the compounds for the biosynthesis of protein were increased by eO3 and the metabolism of N was enhanced through the increased activities of foliar enzymes (Yamaguchi et al, 2007).…”

“…In a previous work, we studied the re-translocation of foliar nutrients compared with only midsummer and leaf senescence period in deciduous broad-leaved trees with typical shoot development in responses to eO3 and soils (Shi et al 2016a). From previous results, it is expected that retranslocation of the studied elements under poor nutrition soil without toxic substances are likely more effective in beech species due to its determinate shoot growth pattern and the foliar stoichiometry in beech species is supposed to be more sensitive to eO3.…”