Estimation of Tissue Construction Cost from Heat of Combustion and Organic Nitrogen Content

Abstract

We present a method for estimating the construction costs of plant tissues from measurements of heat of combustion, ash content, and organic nitrogen eontent. The method prediets glucose equivalents, the amount of glucose required to provide earbon skeletons and r-eduetant to synthesize a quantity of organic produet. Glueose equivalents have previously been ealculated frorn the elemental eomposition of tissue. We define construetion cost as the amount of glueose requir-ed to provide carbon skeletons, reduetant and ATP for synthesizing the organie eompounds in a tissue via standard biochemieal pathways. The fraetion of the total construetion eost of a eompound or tissue (excluding costs of transporting eompounds) that is reflected in its glueose equivalents is the biosynthetie efficieney (£"). This quantity varies between 0.84 and 0.95 for tissues with a wide range of compositions. Using the new method, total eonstruetion cost ean be estimated to +6% of the value obtained from bioehemical pathway analysis.Construction costs of leaves ot" three ehaparral species -were estimated using the proposed method and compared to previously published values, derived using different methods. Agreement among methods was generally good. Differenees were probably due to a eornbination of inaeeuracy in the estimated biosynthetie efficiency and teehnieal difficulties with bioehernieal analysis, one of the older methods of determining construction cost.

Comparison of leaf construction costs in woody species with differing leaf life‐spans in contrasting ecosystems

“…The value used in this study for Eg was 0.89 (Williams et al , 1987). In the calculations, we assumed that the nitrogen source was nitrate for all the species, as it is the principal source of nitrogen that is available to higher plants under most field conditions ( Taiz & Zeiger, 1991).…”

“…The value of Hc is determined by the chemical composition of the tissue ( Williams et al, 1987). Fig.…”

“…the construction cost, CC ). The construction cost includes the glucose required to build carbon skeletons, and the glucose consumed in respiration to supply reductant and ATP for energy-requiring processes in the biosynthesis of the tissue constituents (Penning de Vries et al , 1974;Williams et al , 1987).…”

“…Finally, because of the diversity of methods used to calculate CC , a comparison of the available data from different literature sources is unlikely to be a good method to test the hypothesis of whether CC differ among contrasting species and /or between contrasting environments. For example, comparisons of CC values obtained by different methods for the same plant material may differ by as much as 20% ( Williams et al , 1987;Griffin, 1994).…”

Atividade ATPásica e pirofosfatásica em microssomos de raízes de milho colonizadas com fungos micorrízicos arbusculares

“…Assim, a indução deste sistema regenerador de ATP durante a interação micorrízica pode ser parte da resposta adaptativa da planta ao estresse decorrente do consumo da sacarose radicular pelo FMA. De fato, é bem conhecido que, nos estádios iniciais do estabelecimento da colonização micorrízica, geralmente ocorre uma inibição do crescimento da planta (Smith & Read, 1997;Williams et al, 1987), o que também pode ser relacionado com o estresse inicial, causado pela colonização do FMA na raiz hospedeira, e com o consumo de carbono fotossintetizado pela planta antes que essa venha a usufruir os benefícios da associação micorrízica.…”