Effect of pre-incubation humidity and temperature treatment on the in vitro germination of avocado pollen grains

Optimum in vitro germination of pollen grain of the avocado cultivars Fuerte, Nabal, Ettinger, Bacon and Zutano occurred at 25 °C. However, there were significant differences between cultivars in percentage germination and relative humidity (RH) requirements for optimum pollen grain growth. The most sensitive cultivar to relative humidity was Fuerte, in which the germination of pollen grain rose from 11.4%, at 40% RH, to about 50%, after one hour at 100% RH. The germination% of Nabal pollen grain was already high at 40% RH and was not increased by higher relative humidity. Increased relative humidity also helped to sustain the viability of avocado pollen. At 30 °C and 5% RH the pollen grains of Fuerte quickly lost its ability to germinate, at 40% RH for 1 hour, germination was reduced spectacularly compared to pollen kept in saturated with moisture environment where it was not affected the first 24 hours. The effects of temperature and relative humidity on fruit-set and yield of avocado are discussed. This revised version was published online in July 2006 with corrections to the Cover Date.     

Reforestation of degraded Kermes oak shrublands with planted pines: effects on vegetation cover, species diversity and community structure

This paper examines the results of plantings of the Mediterranean pine species, Pinus halepensis and Pinus pinea, in a degraded Mediterranean kermes oak (Quercus coccifera) shrubland in Northern Greece, which were accomplished in order to mitigate ecosystem degradation. Plant establishment and the vegetation differences between the degraded ecosystem’s previous state and the new state following reforestation were measured in order to evaluate the effect of reforestation. Monitoring of the seedling survival and growth of the planted species was carried out during the next five years. In the fifth year we conducted botanical inventories in 18 and 15 plots (50 m² in size) from the reforested and control area, respectively. Plant community parameters estimated were: vegetation composition, total plant cover, planted species cover, native woody, herb and grass species cover, plant species richness, Shannon-Weiner index, community structure and dominant plant height. P. halepensis exhibited higher survival and growth than P. pinea. The reforested area exhibited higher plant diversity, higher vegetation cover, taller plants and more complex community structures than the control area, which concludes that plantings of pines can be successfully used in degraded ecosystem reforestation projects, in areas with similar site conditions.     

Response of Two Olive Cultivars to Salt Stress and Potassium Supplement

ABSTRACT

The effects of saline water containing 0, 50, 100, and 150 mM sodium chloride (NaCl), and 100 mM NaCl + 100 mM potassium (K) on photosynthesis, water relations, and ion and carbohydrate content of olive (Olea europaea L.) cultivars ‘Koroneiki’ and ‘Mastoidis’ were studied on five-year-old trees. Salinity increased sodium (Na⁺) and chloride (Cl^?) in tissues of both cultivars, but more so in ‘Koroneiki’ than in ‘Mastoidis.’ Salt-toxicity symptoms were observed at 100 and 150 mM, but not in plants receiving extra K. In salt-stressed plants, leaf water potential declined, whereas turgor potential remained positive due to a rapid decrease in osmotic potential. Salinity increased mannitol content up to 41.3% in ‘Mastoidis’ and 15.8% in ‘Koroneiki’, but reduced starch content in leaves. Photosynthetic rates fell significantly with increasing salinity in both cultivars, but more so in ‘Koroneiki’ than in ‘Mastoidis’. Potassium supplements reduced the concentration of Na⁺ and increased the concentrations of K⁺ in leaves, but decreased photosynthesis.     

Pituitary adenoma predisposition caused by germline mutations in the AIP gene

Pituitary adenomas are common in the general population, and understanding their molecular basis is of great interest. Combining chip-based technologies with genealogy data, we identified germline mutations in the aryl hydrocarbon receptor interacting protein (AIP) gene in individuals with pituitary adenoma predisposition (PAP). AIP acts in cytoplasmic retention of the latent form of the aryl hydrocarbon receptor and also has other functions. In a population-based series from Northern Finland, two AIP mutations account for 16% of all patients diagnosed with pituitary adenomas secreting growth hormone and for 40% of the subset of patients who were diagnosed when they were younger than 35 years of age. Typically, PAP patients do not display a strong family history of pituitary adenoma; thus, AIP is an example of a low-penetrance tumor susceptibility gene.     

Prediction of planted seedling survival of five Mediterranean species based on initial seedling morphology

Field performance can be predicted by evaluating nursery stock quality, but optimal morphological variables for use in these assessments may vary by species especially under dry Mediterranean conditions. Our objective was to identify initial seedling morphological characteristics that successfully predict field performance of five Mediterranean species (Pinus halepensis, Quercus ilex, Quercus coccifera, Ceratonia silqua and Pistacia lentiscus). Container seedling morphology was evaluated following the nursery phase, and then seedlings were outplanted in the field where field survival was monitored for two successive years. Results indicate that survival can successfully be predicted from seedling initial morphological characteristics for all these species, yet not all the initial characteristics were good predictors. Survival of P. halepensis and Pist. lentiscus seedlings was positively correlated to initial seedling root-collar diameter, total dry weight and Dickson’s quality index, and can be reliably predicted by these variables. In contrast, seedling field survival of the two Mediterranean evergreen oak species was correlated with few initial morphological attributes; initial diameter provided an accurate index to predict second-year outplanting survival for both species while height/diameter was a good survival predictor for Q. coccifera seedlings. For C. siliqua seedlings, seedlings with larger initial diameter and total biomass survive better in the field. Thus, diameter was the common variable that accurately predicted survival for all species, which should be >5 mm for P. halepensis seedlings and >7 mm for the remaining species.     

Development of an adapted empirical drought index to the Mediterranean conditions for use in forestry

The most widely used empirical drought indices in forestry and fire risk management were tested under Mediterranean conditions. These were: the Keetch-Byram drought index KBDI, the Nesterov index NI, the Modified Nesterov index MNI, the Zhdanko index ZI which belong to the cumulative type, and the Sweden Angstrom Index which belongs to the daily type. The above indices were selected for fire risk assessment in the European Mediterranean conditions, following the method of correlating indices with real fuel moisture data. Meteorological data were collected for the testing area of the sub-urban forest of Thessaloniki, northern Greece. Time series of the drought indices were constructed for the summers of 2006 and 2007. At the same time, field data were collected in order to estimate the real fuel moisture content including surface soil, litter to represent the dead fuel moisture content, and grass to represent the live fuel moisture content. Statistical analysis of the collected field data and their correlation with the tested drought indices, which calculated from the local meteorological data, showed that KBDI is the most suitable empirical drought index for the area. Consequently, KBDI was modified for a better adaptation to Mediterranean conditions, following the development procedure as in the original paper. Based on the above method a Modified KBDI was calculated for the study area, and the differences from the original KBDI were estimated. The comparison of the two indices showed that: (a) there is a faster response of the Modified KBDI index to meteorological data, (b) the index takes on higher values during the summer months of both studied years, and thus, previously reported problems of underestimation of actual water loss is mitigated, and, (c) the estimated fire risk is higher for the study area, which is in accordance with the very low moisture content values observed.