Mauro Falusi

Bud dormancy release in elm (Ulmus spp.) clones—a case study of photoperiod and temperature responses

Dormancy release as influenced by duration of outdoor winter chilling in Florence (Italy) was studied under different photoperiodic and temperature treatments in collected twigs of two European (Ulmus glabra Huds. and Ulmus minor Mill.) and four Asian (Ulmus pumila L., Ulmus parvifolia Jacq., Ulmus macrocarpa Hance and Ulmus villosa Brandis) elm clones. Photoperiod had no effect on dormancy release, and there was no evidence that photoperiod affected bud burst during quiescence in the studied elm clones. Thermal time (day degrees >0 degrees C) to bud burst decreased in all the clones with increasing outdoor chilling. Although all the clones exhibited a rather weak dormancy, they significantly differed from each other. Dormancy was released earlier in the Asian than in the European clones, and the clones could be ranked from the U. pumila clone (very weak and short dormancy) to the U. minor clone (relatively stronger and longer dormancy), the other clones being intermediate. In all the clones except U. minor, the observed decrement in thermal time to bud burst was efficiently explained as an inverse exponential function of the number of chill days < or =5 degrees C received outdoor in autumn and winter. Endodormancy, as measured by the single-node cuttings test, was weak and short in all the clones. The latter result suggests that correlative inhibitions were largely responsible for preventing bud burst during winter in these elm clones.

Vegetative bud-burst variability of European elms

The bud-burst dates of clones of Ulmus minor, Ulmus glabra, and Ulmus laevis were recorded in the field during the spring of 2000, 2001 and 2002 at six locations in five European countries. Meteorological data were obtained from stations close to the plots. Thermal time to bud-burst (T) and chilling (C) were calculated. A relationship on the form T=a+b e rC was fitted for each species. In the three species, winter rest release seems to be controlled by two opposite quantitative effects of the temperature, which interrelate according to an inverse exponential relation. Besides, the bud-burst date was found to be stable between years characterised by different winter thermal trends. These three Elm species have small chilling requirements. U. minor has chilling requirements lower than those of the other two species, in agreement with the more southern distribution.

Relations between apical structure and growth patterns in Pinus halepensis Mill, seedlings

Abstract The process of primary growth in 2-year-old seedlings of 11 populations of Pinus halepensis Mill. is described. At the end of the first growing season one type of apical structure was observed: type-1, a tuft of primary needles placed close together, surrounding and protecting a meristematic apex. At the end of the 2nd growing season, three types of apical structure were observed: type-1; type-2, a terminal winter bud; and type-3; a «bud» with characteristics of both type-1 and type-2. Morphological observation along with an anatomical examination of the winter bud led to the conclusion that the definitive growth pattern in juvenile P. halepensis is monocyclic with a variable number of summer shoots. This growth pattern is reached by some P. halepensis populations in 3–4 years, by contrast, in other pine species two years are usually needed. The populations studied differed both in growth potential (differences in number of cycles, ratio of first cycle to total growth, growth rates) and in the de...

Dormancy of Fagus sylvatica L. buds III. Temperature and hormones in the evolution of dormancy in one-node cuttings

ABSTRACT The evolution of the growth potential of Fagus sylvatica L. buds in the autumn-winter period (September-March) was analysed. One-node cuttings (of apical, median and basal buds, and small buds at the base of the branch) were taken from one-year old shoots removed from adult beech plants (at Vallombrosa in the Tuscan Apennines) and placed in climatic chambers with a 12-h photoperiod and temperatures of 15° and 25°C. They were treated either with water or gibberellin and kinetin solutions. The trend in sprouting was followed, for all types of buds, for 60 days. The months of September and October constituted the period of entry into dormancy, which then reached a peak at the beginning of November. In December, the phase of rapid dormancy removal was already present. Restriction and subsequent widening of the thermic interval compatible with growth, establishment and later removal of the basitonal habitus were the characterising elements in the autumn-winter evolution. Kinetin had null or slightly inhibiting effects in all the examined period. Gibberellin did not modify the behaviour of buds approaching dormancy, whereas they strongly stimulated growth in the period of rapid dormancy removal, and exerted moderate effects in the subsequent period of slow residual dormancy removal.

Leaf morphology and bud-burst variation in Ulmus minor from Italy and France

More than 40 Ulmus minor clones were characterised on the basis of 10 foliar morphological traits and budburst phenology in two successive years. Ramets, 4- and 5-years-old, were obtained by means of self-rooted cuttings from elms located in northern, central and southern Italy and in France. Measurements were taken in an open field in the vicinity of Florence (Italy). The morphological traits were found not to be appropriate for describing the variability between clones of different origins, even if some of these traits indicated a xeric adaptation in clones originating from southern Italy. On the contrary, the phenological traits were valid describers of the origin of the clones. Indeed, the southern-Italian clones flushed earlier than the others, while the French clones were more delated. A comparison of the results of the two years showed that the chilling requirements on the trial site were not satisfied. The actual state of knowledge regarding dormancy in the Ulmus genus does not enable to speculate further on the results of this research. Morphological characters seem to show a greater phenotypic plasticity with respect to phenological traits.

Ricerche Sull'Abscissione Nell'Olivo. I. Studio Morfogenetico Dell'Abscissione Fogliare

Abstract Research on the abscission in the olive tree. I. Morphogenetic study on leaf abscission. — The stages bringing the fall of olive leaves can be summed up as follows: 1) starting from the first stages of the leaf development, particularly when occurs the complete differentiation of the procambium and the lengthening of the other cortical cells, it is possible to locate, at the base of the leaf, the abscission zone formed by four or five layers of cells, which differ from those of the nearby areas on account of their smaller size, lack or scarsity of intercellular spaces, thinner cellulose-pectic walls, higher nucleus-cytoplasm ratio, presence of several binucleate cells, and absence of mechanical elements at the level of the vascular tissues. The appearance of thin dividing septa lead us to suppose that in the formation of the abscission zone partake also cellular divisions; 2) when the abscission is on the way, the first changes to be observed are: a) accumulation of starch granules in the absciss...