Self-incompatibility in Spanish clones of apricot (Prunus armeniaca L.) tree
The present study is about some aspects of the reproduction physiology of twenty apricot clones ( Prunus armeniaca L.) grown in Abarán (Murcia, Spain). Self incompatibility of these clones was determined not only in field conditions in terms of the fruit set by means of self fertilization and free pollination, but also in laboratory conditions, by means of fluorescence microscopy of pollen germination on the stigma and of the growth of the pollen tube towards the egg. The only clone with signs of self incompatibility was ‘Moniquí Azaraque’. The clone with the lowest fertilization time was ‘Chicanos Archena’.
Evaluation of pollination as the cause of erratic fruit set in apricot ‘Moniqui’
SummaryApricot (Prunus armeniaca L.) is a species particularly prone to erratic fruit set. However, the causes of this behaviour are poorly understood since the main limitation in the study of erratic fruit set lies in the difficulty of evaluating all its possible causes in orchard conditions. This results in the eradication of interesting apricot cultivars, such as ‘Moniqui’, in spite of their increasing commercial demand due to their good organoleptic qualities. In this work the influence of pollination deficit in erratic fruit set is ascertained in orchard conditions and the self-compatibility and intercompatibility relationships among four of the main Spanish apricot cultivars are also studied. While ‘Moniqui’ is self-incompatible, ‘Bulida’, ‘Canino’ and ‘Paviot’ proved to be self- compatible. Likewise, all the intercrosses between them behave as compatible. An evaluation of both fruit set and pollen tube behaviour in random and supplementary pollinated flowers with pollen from ‘Canino’ in a commercia...
Laser ignition of explosives: Effects of gas pressure on the threshold ignition energy
Abstract This paper describes a method for measuring the effect of initial gas pressure and the type of gas on the threshold ignition energy of several high explosives. The method is based on a 300 W CW CO2-laser. An extensive study of these parameters for PETN and RDX is also presented. These high explosives all show a strong decrease in ignition energy/power with increasing initial gas pressure. The gases tested are air and nitrogen. The studied pressures are in the interval 0.1 to 10 MPa. The ignitability of PETN and RDX was tested at a laser pulse width of 1.2 ms. All tested high explosives had a lower ignition energy/power in air than in nitrogen at low pressures ( 4 MPa). For TNT the time to ignition, measured as a function of air pressure, decreased with increasing pressure. These results are interpreted as a multiple phase ignition process. The method was also used for obtaining ignition data for ...