Ash, Carbon Isotope Discrimination, and Silicon as Estimators of Transpiration Efficiency in Crested Wheatgrass

Abstract

Breeding and selection for higher transpiration efficiency (W) has been hampered by tedious and costly methodology. Rapid and less costly methods are needed for screening W in plant improvement programmes. We report the relationship of ash, silicon (Si) concentration, and Si uptake to W in crested wheatgrass (Agropyron desertorum [Fischer ex Link] Schultes), an important C3 range grass in western North America. Clones of crested wheatgrass were grown under three water levels in a field rainout shelter and as potted plants under two water levels in the field and greenhouse. Ash and Si concentrations were compared to previously determined values of shoot mass, transpiration, W, and carbon isotope discrimination (A). Ash and Si concentrations were not consistently related to A and W across all environments; however, ash concentration was positively correlated with A (r 69 • *, df = 22) and negatively correlated with W (r = -0 . 61**, df= 22) in the well-watered field environment. Across all environments and studies, the ranges in the coefficients of variation (CV, %) for clonal means were: W, 4-15; A, 1-4; ash concentration, 6-14; Si concentration, 13-30; and Si uptake, 21-33. The generally lower CV for W, A, and ash concentration suggest that these traits were more repeatable than Si concentration or uptake. Although a consistent relationship was not observed between Si and W and between ash and W, the correlations of ash and W from the well-watered field environment were encouraging. In view of the low cost for ash analysis, we conclude that further research is needed to evaluate the potential of ash as a criterion in selecting for improved W, particularly during the early phases of a breeding programme when large populations are usually involved. Later selections could be based on the more precise and accurate, but costly, A analysis.

The Effect of Seasonal Variations, Covariations with Minerals and Forage Value on Itchgrass’ Foliar Silicification from Sudanian Benin

“…Phenological stage is well known to influence silica accumulation [48]. The higher leaf SiO 2 content of R. cochinchinensis' is consistent with the hypothesis that silica concentration increases with the plant's age [10,15]. Our study indicates that R. cochinchinensis' increased its SiO 2 concentrations from May to September.…”

“…Alternatively, enhanced silica accumulation might be an inevitable response. It is well known that silica accumulation is correlated to transpiration [15,55]. Tropical leaves with a high photosynthetic capacity may have higher transpiration rates, thus increasing the silica deposition rate.…”

“…Silica may reduce livestock preference or palatability for certain plants [14]. Silicon may also reduce digestibility of fodder grass species [8] by: (i) acting as a varnish on the plant cell wall and reducing access to rumen microflora; (ii) complexing trace elements like Zn and reducing their availability to rumen microflora; or (iii) complexing enzymes that are integrally involved in rumen metabolism [12,15]. Other reports indicate that a water soluble form of Si inhibits activities of some digestive enzymes, but the insoluble form is chemically inert [14].…”

The anomaly of silicon in plant biology.

“…The evidence for that correlation was held to be best for dryland grasses (14). On the basis of nonselective, passive uptake of Si, the Si content of plants might serve as a convenient tracer for water uptake (48), but recent evidence lends little support to a directly proportional relationship between water and Si uptake, even for dryland grasses (49)(50)(51). During its passage through the xylem Si has to remain in solution-i.e., it must remain unpolymerized.…”

Genetic variation in foliar nutrient concentration in relation to foliar carbon isotope composition and tree growth with clones of the F1 hybrid between slash pine and Caribbean pine

“…Foliar N concentration and mineral concentration exhibited significant clonal and/or female and male variations; clonal means of foliar N concentration were significantly related to tree growth; and clonal means of foliar mineral concentration at lower outer canopy were significantly correlated with clonal means of foliar d 13 C at the dry site. Mineral concentration has been shown to be a promising breeding tool for selecting genotypes with contrasting transpiration efficiencies (Masle et al, 1992;Mayland et al, 1993;Araus et al, 1998), and proposed as a surrogate for carbon isotope discrimination owing to its analytical simplicity (Masle et al, 1992;Mayland et al, 1993). Masle et al (1992) reported a positive linear relationship between total mineral concentration of vegetative tissues and either transpiration ratio or carbon isotope discrimination, and a negative relationship between mineral concentration and d 13 C, which were looser for droughted plants or plants fed with nutrient solution of low concentration.…”