D. Ruiz

Changes in inorganic and organic solutes in citrus growing under saline stresses

Abstract Salinity is a key factor limiting cirrus production in many world areas. The two citrus genotypes sour orange (Citrus aurantium L) and macrophylla (Citrus macrophylla Wester), that differ in their ability to restrict sodium (Na) and chloride (Cl) transport to the shoot under salt stress, were studied to compare the contribution of both inorganic and organic solutes in osmotic adjustment. Plants of both citrus genotypes were grown in isosmotic (0.23 MPa) solutions of different ionic composition (Na, NaCl, Cl, and concentrated macronutrients), and leaf and root solutes were measured to determine their relative contribution to osmotic adjustment. Both leaf water and osmotic potentials decreased in response to imposed stress in the nutrient media, regardless of the isosmotic treatment. Growth reduction was more severe in macrophylla than in sour orange, except for macronutrient treatment. The major components associated with the osmotic adjustment were inorganic solutes (ranging from 65 to 85% of tot...

Seasonal progression of bud dormancy in apricot (Prunus armeniaca L.) in a Mediterranean climate: A single-node cutting approach

Abstract The progression of the dormancy of apricot (Prunus armeniaca L.) vegetative and reproductive buds in the summer–winter period (June–March) was analysed with the single-node cutting method during two consecutive years in a Mediterranean climate. The progression of the mean time to budbreak (MTB) was studied. Low MTB values were obtained, which show endodormancy intensity under climatic conditions in the South East of Spain only reached a shallow level in apricot. The onset of bud dormancy occurred prior to the advent of chilling accumulation. Although an oscillating pattern on dormancy progression was observed, MTB increased progressively from summer until January and declined rapidly thereafter coinciding with dormancy breaking, although in 2006–2007, maximum endodormancy intensity was observed at beginning of October. Vegetative and reproductive buds showed a similar pattern of seasonal progression of MTB, although after flower differentiation (ca. September) vegetative buds always showed a deeper dormancy than reproductive buds. Autumn and early winter temperatures seem to play a crucial role over dormancy intensity and dormancy progression. A gradient of increasingly deep dormancy from shoot apex to base is suggested by the gradual increment of MTB in a basipetal direction, although it was influenced by the year.

Temperature efficiency for dormancy release in apricot varies when applied at different amounts of chill accumulation

Our aim was to assess the possible differential effect of increasing temperatures due to global warming on dormancy progression in apricot. The effect of a range of chilling temperatures on vegetative and reproductive bud dormancy progression in excised shoots was examined during two seasons. Temperature treatments were applied in different dormant stages to evaluate the possible interaction of date × temperature for dormancy release in apricot. During sampling, chill accumulated in the field ranged from 0 to 49 chill portions (CPs), corresponding to 0-100% of the chilling requirement (CR) of the apricot selection Z505-2. Forcing conditions were applied after a 60-day chill treatment on each sampling date, and rate to budbreak (1/mean time to bud break: MTB(-1) ) was established in vegetative (terminal and lateral) and reproductive buds to determine depth of dormancy. Results showed that the stage of dormancy has a strong influence on the effect of different temperatures on dormancy progression in apricot. For the first time, a non-linear effect of different chilling temperatures during the dormancy cycle in apricot was obtained, especially in the superior range of temperatures traditionally considered to release dormancy. Thus, introduction of this differential effect could help to improve the models to estimate dormancy release in the context of climate change.