Do changes in carbon allocation account for the growth response to potassium and sodium applications in tropical Eucalyptus plantations?

Understanding the underlying mechanisms that account for the impact of potassium (K) fertilization and its replacement by sodium (Na) on tree growth is key to improving the management of forest plantations that are expanding over weathered tropical soils with low amounts of exchangeable bases. A complete randomized block design was planted with Eucalyptus grandis (W. Hill ex Maiden) to quantify growth, carbon uptake and carbon partitioning using a carbon budget approach. A combination of approaches including the establishment of allometric relationships over the whole rotation and measurements of soil CO(2) efflux and aboveground litterfall at the end of the rotation were used to estimate aboveground net production (ANPP), total belowground carbon flux and gross primary production (GPP). The stable carbon isotope (δ(13)C) of stem wood α-cellulose produced every year was used as a proxy for stomatal limitation of photosynthesis. Potassium fertilization increased GPP and decreased the fraction of carbon allocated belowground. Aboveground net production was strongly enhanced, and because leaf lifespan increased, leaf biomass was enhanced without any change in leaf production, and wood production (P(W)) was dramatically increased. Sodium application decreased the fraction of carbon allocated belowground in a similar way, and enhanced GPP, ANPP and P(W), but to a lesser extent compared with K fertilization. Neither K nor Na affected δ(13)C of stem wood α-cellulose, suggesting that water-use efficiency was the same among the treatments and that the inferred increase in leaf photosynthesis was not only related to a higher stomatal conductance. We concluded that the response to K fertilization and Na addition on P(W) resulted from drastic changes in carbon allocation.     

Plant species richness and ecosystem multifunctionality in global drylands

Experiments suggest that biodiversity enhances the ability of ecosystems to maintain multiple functions, such as carbon storage, productivity, and the buildup of nutrient pools (multifunctionality). However, the relationship between biodiversity and multifunctionality has never been assessed globally in natural ecosystems. We report here on a global empirical study relating plant species richness and abiotic factors to multifunctionality in drylands, which collectively cover 41% of Earth's land surface and support over 38% of the human population. Multifunctionality was positively and significantly related to species richness. The best-fitting models accounted for over 55% of the variation in multifunctionality and always included species richness as a predictor variable. Our results suggest that the preservation of plant biodiversity is crucial to buffer negative effects of climate change and desertification in drylands.     

Genetic changes in durum wheat yield components and associated traits in Italian and Spanish varieties during the 20th century

Twelve field experiments comparing 24 durum wheat varieties from three periods—old (<1945), intermediate (1950–1985) and modern (1988–2000)—were carried out in order to ascertain the advances made in durum wheat yield components and related traits in Italian and Spanish germplasm. Grain yield improvements were based on linear increases in the number of grains per m² and harvest index, while grain weight and biomass remained unchanged. Yield per plant increased at a rate of 0.36 and 0.44% y⁻¹ and the number of grains per m² improved by 39% and 55% in Italian and Spanish varieties, respectively. The mean rate of increase in the number of grains per m² was 0.55% y⁻¹. Plants per m², spikes per plant and grains per spike contributed 20%, 29% and 51%, respectively, to the increase in the number of grains per m². The enhance of the number of grains per m² was due to the greater grain set in the modern varieties, since the number of spikelets per spike remained unchanged. Harvest index increased overall by 0.48% y⁻¹ (0.40 and 0.53% y⁻¹ in Italian and Spanish varieties, respectively). Plant height was the trait that suffered the most dramatic changes (it decreased at a rate of −0.81% y⁻¹, with little difference between the varieties of the two countries), as consequence of the presence of the Rht-B1 dwarfing gene. Harvest index and plant height, which were the traits that most contributed to discriminating between periods, remained unchanged from 1980 to 2000. The higher rates of improvement in Spain are discussed in the context of the contrasting strategies followed to improve durum wheat yield in the two countries.     

Growth response to climate and drought change along an aridity gradient in the southernmost Pinus nigra relict forests

Context

Tree populations at the rear edge of species distribution are sensitive to climate stress and drought. However, growth responses of these tree populations to those stressors may vary along climatic gradients.

Aims

To analyze growth responses to climate and drought using dendrochronology in rear-edge Pinus nigra populations located along an aridity gradient.

Methods

Tree-ring width chronologies were built for the twentieth century and related to monthly climatic variables, a drought index (Standardized Precipitation–Evapotranspiration Index), and two atmospheric circulation patterns (North Atlantic and Western Mediterranean Oscillations).

Results

Growth was enhanced by wet and cold previous autumns and warm late winters before tree-ring formation. The influence of the previous year conditions on growth increased during the past century. Growth was significantly related to North Atlantic and Western Mediterranean Oscillations in two out of five sites. The strongest responses of growth to the drought index were observed in the most xeric sites.

Conclusion

Dry conditions before tree-ring formation constrain growth in rear-edge P. nigra populations. The comparisons of climate-growth responses along aridity gradients allow characterizing the sensitivity of relict stands to climate warming.     

Enhanced growth of Juniperus thurifera under a warmer climate is explained by a positive carbon gain under cold and drought

Juniperus thurifera L. is an endemic conifer of the western Mediterranean Basin where it is subjected to a severe climatic stress characterized by low winter temperatures and summer drought. Given the trend of increased warming-induced drought stress in this area and the climatic sensitivity of this species, we expect a negative impact of climate change on growth and ecophysiological performance of J. thurifera in the harsh environments where it dominates. To evaluate this, we measured long- and short-term radial growth using dendrochronology, photosynthesis and water-use efficiency in males, females and juveniles in three sites in Central Spain. Climate was monitored and completed with historical records. Mean annual temperature has increased +0.2?°C per decade in the study area, and the main warming trends corresponded to spring (+0.2?°C per decade) and summer (+0.3?°C per decade). Radial growth and maximum photosynthesis peaked in spring and autumn. Positive photosynthetic rates were maintained all year long, albeit at reduced rates in winter and summer. Radial growth was enhanced by wet conditions in the previous autumn and by warm springs and high precipitation in summer of the year of tree-ring formation. Cloud cover during the summer increased growth, while cloudy winters led to impaired carbon gain and reduced growth in the long term. We argue that maintenance of carbon gain under harsh conditions (low winter temperatures and dry summer months) and plastic xylogenesis underlie J. thurifera's ability to profit from changing climatic conditions such as earlier spring onset and erratic summer rainfall. Our results highlight that not only the magnitude but also the sign of the impact of climate change on growth and persistence of Mediterranean trees is species specific.     

Bound malondialdehyde in foods: bioavailability of the N-2-propenals of lysine

The lipid peroxidation product malondialdehyde is mostly bound to proteins in foods as an N-2-propenal derivative that is released as N-epsilon-(2-propenal)lysine by digestive enzymes. N-2-Propenals have been identified as the major forms of malondialdehyde in urine. To determine whether available lysine can be released from the N-2-propenals of lysine in vivo, two preparations containing N-epsilon-(2-propenal)lysine and N-alpha-(2-propenal)lysine or N,N'-di-(2-propenal)lysine were synthesized using radioactively labeled lysine and were administered to rats by gastric intubation and intraperitoneal injection. Both preparations were absorbed from the digestive tract, although not as efficiently as free lysine, but most of the radioactivity was excreted in urine. The radioactive label was also readily excreted after intraperitoneal injection. It is concluded that the N-2-propenals of lysine are fairly stable in vivo, so that, although they are absorbed from the gut, most of the absorbed material is not metabolized and is readily excreted as nonavailable lysine.     

Growth of Brazilian Cotton Cultivars in Response to Soil Applied Boron

ABSTRACT

The growth of cotton (Gossypium hirsutum L.) was evaluated in a 6 × 5 factorial experiment with 6 boron (B) levels (0.0, 0.5, 1.0, 1.5, 2.0, and 3.0 mg dm^?3), 5 cultivars (‘CNPA 8H’, ‘BRS Aroeira’, ‘BRS Antares’, ‘BRS Sucupira’, ‘BRS Ipe’), and 3 replications. As B increased in the soil, leaf B concentrations increased linearly in ‘BRS Aroeira’ and ‘CNPA 8H’, and quadratically in ‘BRS Ipe’ and ‘BRS Sucupira’. The concentrations of B in the leaves and in the soil increased with the B increasing in the soil. The agronomic characteristics evaluated showed ‘BRS Aroeira’ and ‘BRS Sucupira’ responding more and BRS responding less to the B doses applied. The variation in the effFiciency of B utilization was: ‘BRS Aroeira’ > ‘CNPA 8H’ = ‘BRS Antares’ > ‘BRS Sucupira’ > ‘BRS Ipe’. Cultivar ‘BRS Aroeira’ had the greatest potential to respond positively to the addition of B to the soil.