TRANSTENSIVE ORIGIN OF THE ENCADENADAS-VALLIMANCA CORRIDOR (BUENOS AIRES, ARGENTINA): A REVISION AND A NEW PROPOSAL FROM SATELLITE IMAGES

The Encadenadas-Vallimanca Corridor (EVC) corresponds to a morphostructural linear feature defining the northern boundary of the Sierra de la Ventana and Tandil hills in the Buenos Aires province. The scarcity of concluding geological studies has resulted in diverse tectonic and hydrographic interpretations regarding the genesis of the corridor. A new analysis of surface morphology, mainly derived from satellite imagery, led to the identification of a series of gentle and elongated en échelon left-stepping relief features or ridges with cross-sectional asymmetric flanks, having an average length of 20 km and oriented sub-latitudinally at 20° to the ENE strike of the corridor. The arrangement of these ridges reminds a tectonic scenario of right-lateral transcurrent faulting, for which, the limiting parallel faults fulfill the function of synthetic Riedel type shear. Besides, the cross-sectional asymmetry of the ridges suggests extensional normal faulting coherent with a transtensional right-lateral flower structure. Shallow seismicity of Mw 4.0 registered by the year 2016 in the proximities of the lineament could suggest recent fault activity. Also, previous gravity potential field mapping in the area seems to highlight basement anomalies underneath the sedimentary cover, coinciding with the main lineament of the Corridor. Based on all this information, the EVC is considered to be the surface expression of dextral transtensional fault activity.

APPLE TREES YIELDING AND FRUIT QUALITY DEPENDING ON THE CROP LOAD, BRANCH TYPE AND POSITION IN THE CROWN

The study was conducted from 2013 to 2015 on 10–13-year-old apple trees cv. ‘Szampion’ (M.9. rootstock) in experimental orchard of Department of Pomology, University of Life Sciences in Lublin. On the trees intensively flowering in 2013, the thinning treatments were performed as follows: thinning at the pink bud stage to the 50% of flower clusters leaving only a king flower in the remaining flower clusters; thinning at the pink bud stage to the 50% of flower clusters leaving only one lateral flower in the remaining flower clusters, thinning 4 weeks after full bloom to the 50% of fruit clusters leaving only a fruit from king flower in the remaining fruit clusters, thinning 4 weeks after full bloom to the 50% of fruit clusters leaving only one fruit from lateral flower in the remaining fruit clusters. Intensively flowering control trees in 2013 and poorly flowering trees in 2013 were left unthinned. The best results in terms of regularity of yielding and high-quality fruits after thinning at pink bud stage to king flower, were obtained. The largest fluctuations in yields were observed with the control tree that flowered poorly in the beginning of the study. It was found that the cultivar ‘Szampion’ is characterized by equal distribution of fruits in lower and middle parts of crown, however in the top of crown, the amount of fruits is significantly lower. Apples with the largest mean fruit weight were from spurs on wood older than two years. However the best flesh firmness, soluble solids and dry matter content was detected in fruits from brindles.

In vitro Propagation and Plantlet Regeneration from Doritaenopsis Purple Gem ‘Ching Hua’ Flower Explants

The effects of four types of explants removed from 10-cm flower stalks of Doritaenopsis Purple Gem ‘Ching Hua’ (immature apical flower buds, immature lateral flower buds, flower stem nodes, and flower pedicel sections) and combinations of two plant growth regulators [naphthalene acetic acid (NAA) and thidiazuron (TDZ)] on direct in-vitro shoot induction and multiplication were studied. Immature apical flower buds were the only explants that showed induction and multiplication of shoots in vitro. NAA at 5.4 and 10.7 μm combined with either 4.5 or 9.1 μm TDZ provided the fastest and greatest percentages of shoot induction (27% to 40%) and the greatest numbers of shoot multiplication (111–160 shoots per explant). In vitro–induced shoots were rooted on medium containing 5.4 μm NAA and developed into plantlets with normal vegetative and reproductive morphology. Regenerated plantlets were acclimatized, showing 100% survival and establishment in greenhouse. Plantlets were grown to maturity and showed normal flower morphology. No floral off-types were observed. The high rates of shoot multiplication obtained offer a means for mass clonal propagation of this and possibly other related Doritaenopsis hybrids.

614 PB 290 FLOWER BUD POSITION DETERMINES BLOOM AND FRUIT CHARACTERISTICS IN `ROME BEAUTY' APPLE

The influence of flower bud position on bloom, fruit quality, and fruit maturity was investigated on `Rome Beauty' apple (Malus domestica Borkh.). Limbs on trees containing spur terminal flower buds and lateral flower buds were tagged and the number of blossoms counted every three days until bloom ended. At harvest, fruit from each bud type were selected and seed number, fresh weight, fruit quality characteristics, and onset of ethylene production were measured. Spur terminal flower buds began blooming earlier, blossomed for a longer period of time, and produced more blossoms than lateral flower buds. Fruit from spur terminal flower buds had more seeds, were heavier, and contained more starch than lateral bud fruit. Lateral bud fruit had higher pressure values, due to smaller size, and higher soluble solids, due to consumption of starch reserves. Fruit color and titratable acidity were not significantly different regardless of bud position. Spur terminal fruit started producing ethylene eight days later than lateral bud fruit, indicating they were maturing less quickly. Cultivars such as `Fuji', `Gala', and `Braeburn' display similar growth and fruiting habits.

Gibberellin-like activity in shoots of Salix pentandra as related to the elongation growth

Activities of acidic gibberellin(GA)-like substances in shoots of Salix pentandra trees growing under natural conditions (69°39′ N, 18°37′ E) were studied in relation to shoot elongation and tip abscission. Bioassay after separation on SiO2 partition columns was accomplished with the lettuce hypocotyl and dwarf rice 'Tan-ginbozu' assays. The GA-like activity in the apical part of the shoot greatly decreased before cessation of growth and shoot tip abscission. In the basal part of the shoot the marked reduction of GA-like substances occurred well before shoot tip abscission and even before shoot elongation had ceased. Low GA-like activity in the shoot may be a prerequisite for apical growth cessation and for the development of lateral flower buds.