The cost of stress resistance: construction and maintenance costs of leaves and roots in two populations of Quercus ilex

Abstract

We tested whether growth and maintenance costs of plant organs vary with environmental stress. Quercus ilex L. seedlings from acorns collected from natural populations in the northern Iberian Peninsula and in a lower elevation and putatively less stressful habitat in the southern Iberian Peninsula were grown in pots under the same conditions. Growth and maintenance respiration were measured by CO(2) exchange. Young leaves from 5-month-old seedlings of both populations had similar mean specific leaf areas, nitrogen and carbon concentrations and specific growth rates, and almost identical growth costs (1.26 g glucose g(-1)). Leaf maintenance cost was higher in northern than in the southern population (27.3 versus 22.4 mg glucose g(-1) day(-1), P < 0.01). In both populations, leaf maintenance cost decreased by 90% as leaves aged, but even in mature leaves, the maintenance cost was higher in the northern population than in the southern population (3.38 versus 2.53 mg glucose g(-1) day(-1), P < 0.01). The growth costs of fine roots < 1 mm in diameter were similar in the two populations (1.20 g glucose g(-1)), whereas fine root maintenance cost was higher in the northern population than in the southern population (9.86 versus 7.45 mg glucose g(-1) day(-1); P < 0.05). The results suggest that the cost of organ maintenance is related to the severity of environmental stress in the native habitat. Because the observed differences in both leaves and roots were constitutive, the two populations may be considered ecotypes.

Root order-based traits of Manchurian walnut & larch and their plasticity under interspecific competition

“…However, increased root respiration rates can also be a direct driver of competition affecting soil CO 2 concentrations and thus inhibiting growth of neighboring roots 80 . The increased respiration in larch root tips in mixture could also be related to their increased cortical tissue 81 , or to higher respiratory costs for metabolic defense and repair mechanisms 82 – 84 . Concerning the latter, the decrease in root respiration in Manchurian walnut could then be related to the reduced concentration of toxic juglone in mixed plantation soil 85 – 87 .…”

Chemical composition of lignocellulosic biomass in the wood of Abies religiosa across an altitudinal gradient

“…As Whittaker has pointed out, all species present optimum growth and higher competitiveness at some point in the environmental gradient [55]. Tree growth conditions determine the chemical composition of tissues and, in less stressful environments, tend to help the production of less costly energy substrates (such as cellulose) over more costly ones (such as hemicellulose and lignin) [31,56,57]. This energy savings may lead to the benefit of other physiological processes, such as growth and reproduction [58].…”

Evaluación y comparación de las respuestas fenológicas, morfológicas y ecofisiológicas de 4 especies de Quercus típicas de los bosques del trópico seco (Paisaje Terrestre Protegido Miraflor-Moropotente – Nicaragua)

“…SLW variation also reflects the climatic conditions: plants that cope with lower water availability, or at least with longer periods of drought along the year, tend to develop thicker and harder leaves (Laureano et al, 2008). This is because a reduction of the relative surface area means a reduction of the ways to lose water, even if for some species an opposite pattern has been observed (Aspelmeyer & Leuschner, 2006).…”