Leaf life span and the mobility of “non-mobile” mineral nutrients – the case of boron in conifers

Abstract

Nutrient conservation is considered important for the adaptation of plants to infertile environments. The importance of leaf life spans in controlling mean residence time of nutrients in plants has usually been analyzed in relation to nutrients that can be retranslocated within the plant. Longer leaf life spans increase the mean residence time of all mineral nutrients, but for non-mobile nutrients long leaf life spans concurrently cause concentrations in tissues to increase with leaf age, and consequently may reduce non-mobile nutrient use effi ciency.Here we analyze how the role of leaf life span is related to the mobility of nutrients within the plant. We use optimality concepts to derive testable hypotheses, and preliminarily test them for boron (B), a nutrient for which mobility varies among plant species. We review published and unpublished data and use a simple model to assess the quantitative importance of B retranslocation for the B budget of mature conifer forests and as a mechanism for avoiding toxicity.

Concentration of elements in silver fir (Abies alba Mill.) needles as a function of needles’ age

“…Earlier investigations showed that the concentration of Ca in needles increased almost linearly at sites with high Ca level in the soil (Wyttenbach et al 1995a), whereas other results revealed its erratic behavior (Wyttenbach et al 1995b). The results of other research studies summarized by Aphalo et al (2002) showed nonlinear increase in the Ca concentration in needles of Scots pine and lodegepole pine, but almost linear increase of these elements in Norway spruce. Borer et al (2004) put forward a hypothesis that the permanent chemical sequestration of Ca is an inducible response to the excess of available Ca, but not a constitutive process, in foliage of Picea rubens.…”

“…These differences are well know and have influenced the selection of the sampling procedure, for monitoring purposes, needles of the equal age were analyzed (Mulgrew and Williams 2000;Stefan et al 2000), whereas differences in the content of elements between needles of a different age were analyzed and discussed in the context of the environmental pollution (Bäucker et al 2003;Rautio and Huttunen 2003;Nakatani et al 2004;Kuang et al 2007) or effects of fertilization of stands (Lehto and Mälkönen 1994;Aphalo et al 2002).…”

Micronutrient levels in some temperate European tree species: a comparative field study

“…The micronutrient requirements of Betula pendula Roth. seedlings have been extensively studied in a controlled environment (Göransson and McDonald 1993;Göransson 1993Göransson , 1994Göransson , 1998Göransson , 1999, but in general coniferous species, and Norway spruce in particular, have received much more attention than deciduous forest species (Madgwick et al 1990;Van Dijk and Bienfait 1993;Linder 1995;Braekke 1994;Nihlgård et al 1997;Wyttenbach and Tobler 1998;Thelin et al 1999;Schleppi et al 2000;Aphalo et al 2002). Bergmann (1992) gives the same optimum ranges of micronutrients for all deciduous forest trees, making no differentiation between species.…”

Retranslocation of nutrients in relation to boron availability during leaf senescence of Betula pendula Roth

“…Apparently B accumulated in stems during the growth season, not during the autumn. Since a large pool of B is recycled through litter, the growth of trees may be limited due to a B deficiency, especially in the spring when the soil is frozen and/or when soil is B deprived (see also Aphalo et al 2002). Yet, stems contained rather substantial amounts of B that may act as mobile reserves to be utilized in spring.…”

“…Now, however, it is well established that B mobility differs across plant species (Brown and Shelp 1997;Lehto et al 2004). Plants that do not retranslocate B at all, or that have a restricted B mobility, are more susceptible to B deficiency than plants able to retranslocate B from mature tissues to sink organs (Dell and Huang, 1997;Aphalo et al 2002;Liakopoulos et al 2009). …”