Combined drought and bark beetle attacks deplete non-structural carbohydrates and promote death of mature pine trees

How carbohydrate reserves change in conifers during drought and bark beetle attacks are poorly understood. We investigated changes in carbohydrate reserves and carbon-dependent terpene defenses in ponderosa pine trees experimentally subjected to two levels of drought stress (via root trenching) and two types of biotic challenge treatments (pheromone-induced bark beetle attacks or inoculations with crushed beetles that include beetle-associated fungi) for two consecutive years. Our results showed that trenching did not influence carbohydrates whereas both biotic challenges reduced amounts of starch and sugars of trees. However, only the trenched-beetle attacked trees depleted carbohydrates and died within the first year of bark beetle attacks. While live trees contained higher carbohydrates than dying trees, amounts of constitutive and induced terpenes produced did not vary between live and beetle-attacked dying trees, respectively. Based on these results we propose that reallocation of carbohydrates to terpenes during the early stages of beetle attacks is limited in drought-stricken trees, and that the combination of biotic and abiotic stress leads to tree death. The process tree death is subsequently aggravated by beetle girdling of phloem, occlusion of vascular tissue by bark beetle-vectored fungi, and potential exploitation of host carbohydrates by beetle symbionts as nutrients.

Increased seed carbohydrate reserves associated with domestication influence the optimal seminal root number of Zea mays

Background and AimsDomesticated maize (Zea mays ssp. mays) generally forms between two and six seminal roots, while its wild ancestor, Mexican annual teosinte (Zea mays ssp. parviglumis), typically lacks seminal roots. Maize also produces larger seeds than teosinte, and it generally has higher growth rates as a seedling. Maize was originally domesticated in the tropical soils of southern Mexico, but it was later brought to the Mexican highlands before spreading to other parts of the continent, where it experienced different soil resource constraints. The aims of this study were to understand the impact of increased seminal root number on seedling nitrogen acquisition and to model how differences in maize and teosinte phenotypes might have contributed to increased seminal root number in domesticated maize.MethodsSeedling root architectural models of a teosinte accession and a maize landrace were constructed by parameterizing the functional-structural plant model OpenSimRoot using plants grown in mesocosms. Seedling growth was simulated in a low-phosphorus environment, multiple low-nitrogen environments, and at variable planting densities. Models were also constructed to combine individual components of the maize and teosinte phenotypes.Key ResultsSeminal roots contributed about 35% of the nitrogen and phosphorus acquired by maize landrace seedlings in the first 25 days after planting. Increased seminal root number improved plant N acquisition under low-N environments with varying precipitation patterns, fertilization rates, soil textures, and planting densities. Models suggested that the optimal number of seminal roots for nutrient acquisition in teosinte is constrained by its limited seed carbohydrate reserves.ConclusionsSeminal roots can improve the acquisition of both nitrogen and phosphorus in maize seedlings, and the increase in seed size associated with maize domestication may have facilitated increased seminal root number.

THE PRIMARY METABOLITES OF SARDINE (SARDINA PILCHARDUS) IN THE MOROCCAN NORTH ATLANTIC

Primary metabolites were determined in muscle, liver and gonads in sardines (Sardina pilchardus) captured in the Moroccan North Atlantic.It emerges from this study that in sardines, in the different seasons of the year, the lipid, protein and carbohydrate reserves are stored in the different organs. This important storage of metabolites in the gonads will undoubtedly be used for maturation while the reserves stored in muscle and liver will be used for the production of energy necessary for catadromous migration.In addition, there are other biotic and abiotic factors that influence the use and storage of these metabolites such as the quality and quantity of foods and hydrological parameters.

Dynamics of Starch Reserves in Some Grapevine Varieties (Vitis vinifera L.) During Dormancy

Carbohydrate reserves in grapevine are stored in form of starch and soluble sugars. The present study was conducted in order to understand the dynamics of insoluble carbohydrate reserves during dormancy season of some table and wines grapevine varieties. Six year old grapevine varieties (Muscat de Hamburg, Napoca, Cardinal, Perla de Csaba, Fetească regală, Muscat Ottonel, Pinot noir and Fetească neagră) were sampled before winter. During dormancy, starch level in canes was appreciated by iodin in potassium iodide method, wood and pith diameter measured and bud viability tested. The levels of starch in grape canes at the beginning of dormancy (November) was highest in Muscat de Hamburg (3.89), Napoca and Fetească regală (3.76) and the lowest in Cardinal (3.47). Due to climatic conditions over dormancy, starch began to resynthesize already during January and February, with significantly high levels for all varieties. Wood/pith ratio was highly correlated with starch level. Bud viability was directly influenced by the starch level in canes.