Biomass and nitrogen distribution ratios reveal a reduced root investment in temperate lianas vs. self-supporting plants

Background and Aims The reliance on external support by lianas has been hypothesized to imply a reduction in the biomass cost of stem construction and root anchorage, and an increased investment in leaves, relative to self-supporting plants. These evolutionary trade-offs have not been adequately tested in an ontogenetic context and on the whole-plant scale. Moreover, the hypothesis may be extended to other potentially limiting resources, such as nitrogen (N.) Methods Plants belonging to five con-familiar pairs of temperate liana/shrub species were cultivated in 120 L barrels and sequentially harvested over up to three growing seasons. To account for the ontogenetic drift, organ biomass and nitrogen fractions were adjusted for plant biomass and N pool, respectively. Key Results Lianas invested, on average, relatively less biomass in the root fraction in comparison with shrubs. This was offset by only insignificant increases in leaf or stem investment. Even though liana stems and roots showed higher N concentration in comparison with shrubs, plant N distribution was mostly driven by, and largely matched, the pattern of biomass distribution. Lianas also showed a greater relative growth rate than shrubs. The differences between the growth forms became apparent only when ontogenetic drift was controlled for. These results were confirmed regardless of whether reproductive biomass was included in the analysis. Conclusions Our results suggest that temperate lianas, in spite of their diverse, species-specific resource distribution patterns, preferentially allocate resources to above-ground organs at the expense of roots. By identifying this trade-off and demonstrating the lack of a general trend for reduction in stem investment in lianas, we significantly modify the prevailing view of liana allocation strategies and evolutionary advantages. Such a resource distribution pattern, along with the cheap unit leaf area and stem unit length construction, situates lianas as a group close to the fast acquisition/rapid growth end of the life strategy spectrum.

Heteroblasty in bromeliads - anatomical, morphological and physiological changes in ontogeny are not related to the change from atmospheric to tank form

Heteroblasty is defined as an abrupt change in gross morphology during ontogeny, whereas homoblastic species show no or gradual changes. For Bromeliaceae, there are conflicting reports on a very limited number of species on the functional importance of this step change compared with gradual changes (ontogenetic drift). Studying a large set of species should allow more general conclusions. Seventeen homoblastic and heteroblastic species from Panama were investigated, including the entire size range of most species. Measurements included functionally relevant anatomical (water storage tissue), morphological (stomatal and trichome densities) and physiological parameters (transpiration rates, nutrient uptake rates). Size-related variation in all parameters was common, but evidence for a step change in the studied parameters could not be detected in any of the heteroblastic species. Our results caused us to question the widely held view of the course of the ontogenetic development in heteroblastic bromeliads and their functional implications. These findings suggest that the possible functional relevance of heteroblasty in bromeliads require rethinking and future investigations should employ a comparative approach with both homoblastic and heteroblastic species and including the entire size range to account for ontogenetic drift.

On-farm assessment of environmental and management factors influencing wheat grain quality in the Mallee

We used data from 63 grower-managed wheat crops during 3 growing seasons in the Mallee to explore grain protein responses to environmental and management factors. Allometric coefficients were calculated as the slope of the regression between the mass of log-transformed protein and non-protein grain components to account for the effect of ontogenetic drift on grain protein concentration. Test weight and screenings were also investigated. Grain protein concentration ranged from 8.7 to 16.2%; 90% of crops had less than 5% screenings, and 95% had test weight above 74 kg/hL. Screenings increased and test weight declined with increasing concentration of protein, particularly for protein concentration above 13%. Fourteen cultivars were represented in the sampled crops. In comparison with crops of varieties eligible as Australian Premium White, crops of hard wheats had greater protein content, more screenings, lower test weight, and a greater protein : non-protein allometric coefficient, indicating differences in the pattern of protein allocation between these groups of cultivars. Protein concentration declined with increasing yield at a rate �1%/t.ha. It decreased with increasing seasonal rainfall at a rate of 0.014%/mm, and increased with the proportion of water stored below 0.5 m at a rate of 0.121%/%. Delayed sowing between mid April and mid July generated a size-dependent increase in grain protein concentration of 0.027%/day. Increasing protein content could attenuate the profit lost due to delayed sowing by up to AU$39/ha in hard wheats. Wheat grown after legumes accumulated 64% more protein and 47% more non-protein material in the grain than their counterparts grown after cereal, and grain protein concentrations averaged 13.3 and 12.2% respectively. Protein concentration was unrelated to the amount of nitrogen in the whole soil profile (0-1 m), and weakly associated with the amount of initial nitrogen in the 0-0.1 m soil layer; it increased at a rate of 0.038%/kg N.ha. Chemical constraints in the subsoil probably affected the ability of the crop to use, and contributed to the accumulation of nitrogen in deep soil layers.