Ciclo Di Accrescimento E Differenzazione Delle Gemme in Piante Perenni Nel Territorio Di Bari

Summary

The evolution of cambial activity during one year in Viburnum Tinus L. in Bari has been studied. The research seems to be particularly difficult in this evergreen shrub. The wood is of the porous diffused type with scarse evidence of wood rings. The vessel diameter varies rather irregularly in the wood ring; on the other side the fibers show wide variations and may be assumed as a good index of the wood ring evolution. Both in the branch and in the stem only one wood ring each year is formed.

Cambial activity prosecutes during the whole year, with an irregular step. During the period July-beginning of September the cambium devides very slowly, or possibly stops deviding.

The early wood is produced earlier in the branch than in the stem; namely in February-end of May in the branch and in March-beginning of June in the stem. The stimulating growth stuffs evidently proceeds downwards from the top to the base of the plant. The relations between ring evolution and climatic factors are discussed. The peculiar cambial poussée during the month of June seems to be correlated with the exceptionally aboundant rainfall of May in Puglia in 1947.

The late wood is formed during the other months discontinuosly. The alternation between the two phases of cambium division and wood lignification has been focussed. The wood ring in Viburnym Tinus is annual and the early wood differentiates in spring.     

Studio Del Ritmo Vegetativo Di Olea Europaea L. in Messina Negli Anni 1952–54

Summary

The vegetative growth of the olive tree in Messina is described. The growth period begins at the end of March and prosecutes without interruption as late as November. The secondary wood tissue producted during summer time (from Yuly to August) is abnormal being of a parenchimatoide type. During winter there is a well defined rest period.

The cambium produces secondary wood and bark with an alternate rythm, so that in spring the wood production prevails on the liber and in autumn the opposite condition is realized.

Each phase of production of secondary conducting tissues (wood as well as bark) is followed by a phase of starch storing.

In the stem several false wood rings are produced during one year, while in the young branches each wood ring corresponds to one year.

The longitudinal growth and cork formation on the branches of the year are particularly pronounced during spring (March-May).

Cambium cells swell in a characteristic way before they start dividing and collapse during the resting periods, thickening evidently their walls, so that in winter it is difficult to distinguish a cambial cell from a parenchimatic one.

The behaviour of the vegetative growth of the olive tree in Messina is discussed on the base of the climatic characters of the region.     

Alcuni Aspetti Della Variabilità Del Legno Secondario Di Un Esemplare Di Prunus Persica Stokes

Abstract

Some aspects of the variability in wood structure of a specimen of PRUNUS PERSICA Stokes. — The secondary xylem of a young stem of Prunus persica Stokes has been investigated under three main headings: 1) vessel and fibre length; 2) intrusive fibre growth; 3) relative amount of libriform fibres, fibretracheids and tracheids.

Vessel members and fibres have been reckoned from single rings and from the whole wood body.

The relation between the above mentioned dimensions and the position within the wood body and the width of the growth layers has been calculated.

No remarkable variation has been found along the axis of the stem; on the contrary there is a decrease in both fibres and vessels length along the radius of the stem from inside outwards. Such behaviour having never been recorded before, the possible causes are suggested.

A positive correlation has been found between the width of the growth layers and 1) vessel members and fibres length, 2) fibre intrusive growth, 3) percentage of libriform fibres. In addition a relative correlation between percentage of libriform fibres and age of the cambium has been put in evidence.     

Osservazioni Anatomiche su Pini Sottoposti a Resinazione

Summary

Specimens of Pinus halepensis, from the forest of Patemisco Gallio (Taranto) which were tapped, have been studied. The following conclusions have been reached

The control specimens formed a double ring from May to October.

The specimens which were chipped with the scraper (herring-bone method) show a strong acceleration of the wood ring formation. From May to October three rings are formed, each with its own resin ducts, but these channels are atypic, different from those of the ase tapping. The accelerating stimulus caused by the scraper is transmitted at lower levels, as the wounding proceedes from the upper region downwards. Considering that the successive wounds reache, by and by, regions of the stem aready accelerated in cambium activity, the summing up of the successive stimuli causes a sort of exhaustion of the cambium, so that the last rings are rather narrow with irregular and poor resin ducts.

The specimens chipped with the axe (french method) formed a double wood ring like the control ones, showing only a slyght acceleration in comparison with the control specimens. This fastening of the wood ring formation does not transmit neither upwards nor tangentially. The resin ducts in the wounded wood are formed in their normal anatomical region, they are more numerous and bigger than those of the control.

Conclusively: in the axe system the resin ducts are hudge and numerous and the rhytm of the cambial activity is the same as in the control specimens. In the scraper system an acceleration of the cambium activity occurs, with the formation of several wood rings during one tapping season, but the resin ducts are poor and irregular.     

Osservazioni Sull'attività Cambiale Di Nerium Oleander L.

Abstract

Observation on the cambial activity in «Nerium oleander» L. — The cambial activity of «Nerium oleander» has been observed in three localities in Southern Italy: Bari and Lucera, where the oleander is cultivated, and Policoro, in the bed of the river Sinni, where the oleander is spontaneuos. The wood is of the diffuse-porous type. Growth rings corresponding to distinct periods of growth are not distinguishable, as there are no easily distinguishable types of wood (early, intermediate, and late wood). Only occasionally the uniform wood is interrupted by narrow circular bands of a few layers of radially compressed cells. Differences in the behaviour of the cambium have been observed in the three localities. At Policoro there was a long period of activity from the middle of March until November without interruptions. At Bari the cambium was active from the middle of March until the first days of April; after a pause it was active again from the second half of May until die middle of July and again during the second half of September-October and the first ten days of October. In 1957 a slight activity was noticed also during about twenty days in December. At Lucera the active period as compared with Policoro was still shorter than at Bari; in the spring there was a delay in the resumption of activity, while the summer rest period lasted until the middle of October. The cambium was then active again until the first days of November. Some of the differences in the behaviour of the cambium in the three localities could perhaps be explained by climatic or pedologic factors, such as the rich water table in the case of the plant growing in the Sinni bed. In conclusion «N. oleander» seems to be a species adapted to a sub-tropical climate, without distinct growth rings.     

Ciclo Di Accrescimento e Differenziazione Delle Gemme in Piante Perenni Nel Territorio Di Bari

Summary

Growth CYCLE AND BUDS DIFFERENTIATION IN PERENNIAL PLANTS GROWING IN Bari AREA. 1) Observations ON Ficus Carica DURING THE YEAR 1946.

The fig tree under observation in Bari started its growth (during the year 1946) in the second week of March and stopped in June second half. The growth period lasted about three months (tab. 1 e 2; diagr. 1).

The most rapid growth occurred during the second week of May (tab. 2; diagr. 1).

From the diagr. 3 it appears that in the fig tree the growth end corresponds at the beginning of the rainless weather; in the meantime the temperature rises gradually (diagr. 4). The atmospheric humidity subsists high also during the summer rainless period (diagr. 5).

Among the four shoots examinated, only one showed a further slow lengthening (13 mm.) from 2nd. August to 6th September. The three others did not grow anymore from June 15 (tab 2; diagr. 1).

The young shoot internodes have different lengths. The basal ones are shorther than the middle ones, which appeared during this speedly growing period (diagr. 2); the last two internodes are very short, so that the nodes are rather contiguous. At each node one leaf unfolds, with two large stipules, which soon fall; on the very last node the stipules do not fall, sheltering the young apical bud, which they completely close in. The corresponding leaflet scarsely grows, falling soon. Neverthless the protection of the two stipules, the first leaflet of the apical bud withers and falls frequently as soon as the bud unfolds at the beginning of spring (fig. 1).

Each leaf axil bears two or three buds (fig. 7). When two buds are present, one is a fruit bud and the second a vegetative one (figg. 11 e 13), when three buds are present, the two lateral ones develop into flowers, while the middle one grows into a vegetative shoot (fig. 12).

The very first sign of the fruit character of a bud is the flattening of the apical bud meristem (fig. 7); successively it deeps into a cuplike body (figg. 8 and 9); on the bottom and along the walls of the cup the female floscules are developing (fig. 10).

The first sign of the vegetative character of a bud is, after the formation of the leaf meristem outline, its evolution with the caratteristically lobed leaves and stipules.

As far as a given height along the shoot (as far as the sixth node in our shoots) the syconia prolong their growth after the shoot lengthening has stopped and ripen completely during August-September (forniti or September-figs). From a certain level ahead, as far as the apical bud (from the seventh to the tenth node in our shoots) the syconia cease their development about contemporarly the vegetative shoot. They are three or four mm. wide and the little flowers are clearly distinguishible inside. So they hang from the nodes as late as next spring time, when they begin to grow again, ripening in June (fioroni or June-figs).

September and June figs then represent a continous acropetal fruit series differentiating at each leaf axil, as soon as the leaflets unfold during the shoot development. We must point out that while the September figs reach the ripe condition through a stopless development in the same year, the June figs stop their growth at a given time, standing a resting period and begin to grow again, ripening the next vegetative season.

As to explain such a behaviour, the presence of an inhibitory stuff is prospected, produced from the more developed figs, which attain a given stadium of development. This stuff would act on those figs, which have not yet reached this particular development stage.

The summer drought checkes the shoot growth and the bud differentiation. The flower buds, which have been too early stopped in their development, are not able to grow again the next season and fall during the apical bud unfolding. Such a condition occurs in the last leaf bud (fig. 4) and in the first leaflet bud inside the vegetative tip (apical bud) (fig. 5). At the beginning of the new vegetation season the shoot awakes with the differentiation of those buds, which did not yet differentiate at the axil of the leaflets inside the apical bud (fig. 6). (See fig. I, where the phenomenon is schematically reproduced).     

Andamento Dell'Accrescimento Del Legno in Ceratonia Siliqua L.

Abstract

The woody tissue of Ceratonia siliqua is of the diffuse-porous type, being mainly constituted of fibres full of starch grains (sostitution fibres; fusiform cells of the wood parenchyma).

The wood formed throughout the year is uniform and the annual rings are hardly distinguishable except for the presence of apotracheal parenchyma. The cambium shows a marked activity from May to July, and a less pronounced one from July to September; it is hardly or not at all active from October to April. During these latter months the cambium is completely dormant only in January, while during the others, especially the ones prior to the late spring reawakening, it can function in localised areas for short lapses of time.

These observations have been carried out in a female plant cultivated in Apulia, a region where Ceratonia siliqua is not a normal component of the natural plant cover. It is of some interest therefore to compare them with what is known of the same species in Israel, where C. siliqua is a spontaneous element of the maquis vegetation. The behaviour of the cambium of C. siliqua is similar in both regions but in Israel the maximum of activity begins earlier in the year and last for a longer period (mid-April to mid- August), after which the cambium becomes gradually less active until its activity is reduced to a minimum during autumn and winter. A short period of dormancy precedes the spring-time reawakening. This subcontinuous activity of the cambium together with the occurrence of flowering time in autumn-winter shows C. siliqua to be a tropical type of plant, but is nevertheless in good agreement with the eastern mediterranean climate.

In Apulia on the other hand we notice that the subcontinuous activity of the cambium is more potential than real, giving rise to sporadic and localised episodes from October to May. While this and other differences can be interpreted as direct responses to local climatic conditions, the general disturbances in the vegetative cycle can not be explained in the same way. In other words while the tendency of the cambium to remain dormant from October to May is probably caused by the relatively severe winter conditions, the shorter period of functioning in the spring—summer, the full resting period occurring in January rather than in February-March, and the attempts to resume meristematic activity already in February, while the full reawakening only occurs in May, can only be ascribed to indirect climatic action. These disturbances are probably to be seen as conseguences of the fact that the climatic conditions during the Apulian summer allow the flowers, whose primordia are well evident in July, to blossom in October-November and exceptionally even in August that is at least one month earlier than in Israel, where flowering occurs in December. This alteration in the flowering time affects the rythm of cambial activity causing it to be out of phase with the climatic cycle.

C. siliqua appears therefore not to be perfectly adapted to the Apulian climate even though it can often be found where it could not possibly have been planted, as on the steep flanks of fairly deep gulleys, and can be considered to be at least sub-spontaneous.     

Ciclo di Accrescimento E Differenziazione Delle Gemme in Piante Perenni Nel Territorio di Bari

Summary

Growth cycle and buds differentiation in perennial plants growing in Bari's area. — V. The evolution of the wood ring in Rhammus Alaternus L. from December 1946 to March 1949.

In Rhamnus Alaternus L. the cambium awackens in March with the production of an early wood, characterized by large vessels and loose fibers. It keeps on dividing the following months, producing intermediary wood, whose vessels become narrower and narrower. In June the wood ring is almost complete and the cambial activity slows down. In July late wood is formed, with narrow tracheae and highly lignified fibers. From August to February cambial activity is very scarce and irregular, in the wood produced fibers being tangentially compressed.

In a young branch of R. A. cambium becomes suddenly active in February, that is one month before than in the stem, it goes on during the month of March-June, with an evident diminution in the size of the wood elements. This diminution of size instead of being regular, shows some oscillations, expecially during the month of May. In Sept. the cambium starts again dividing, but rather poorly and irregularly, forming some vessels a little wider than the preceeding ones, so that an incomplete false ring is formed only in some points of the branch. As a rule the autumn wood is a typical late wood. This scarce and irregular cambial activity goes on also during Oct.-Dec. In January is more active and forms rather wide vessels in comparison with those formed in the preceeding month. This new formed wood however does not show the characteristics of the early wood of a new ring.

Concluding, the characteristics of the cambial activity of A. R. are

In the stem: 1) March: early wood. 2) March-June: intermediary wood. 3) July: late wood, resting period. 4) At the end of Autumn a scarce production of late wood is sometimes possible.

In the young branch: 1) February: early wood. 2) March-June: intermediary wood, with positive and negative oscillations in the vessels width. 3) At the end of June the late wood is already differentiated. 4) July-August: resting period. 5) Spt.-Juan.: the cambium starts again dividing very scarcely and producing a transition wood between the two rings. This wood can be regarded neither as a true ring nor a false one, it represents rather the last phase of the late wood formation. 6) In the young branch of the female specimen the cambium starts dividing somewhat later than in the male one. 7) The wood ring width does not vary much in relation to the yearly amount of rainfall. The lack of relation between rainfall and ring width is particularly evident in 1948 (a rainy year). The, «Compleasance» of R. A. could show that this species is, in Puglia, in its own habitat. On the other hand it is rather peculiar that R. A. forms only one wood ring during one year, with production of early wood during the spring, and of late wood in the autumn, instead of producing a second autumn ring following a distint summer rest, as could be expected.     

Evoluzione Annuale della Cerchia Legnosa in Individui Maschili E Femminili di Ginkyo Biloba L.

Abstract

Wood ring evolution in male and female plants of GINKYO BILOBA L. — A morphological examen of the wood rings in Ginkyo biloba L. has been performed on stem sections from specimens of the Botanical Institute of Florence, on wood samples from the collection of Adriano Fiori and on wood cores extracted from the stem of male and female plants growing in the Botanical Garden of Florence.

At the same time the development of the growth ring has been followed on wood samples tacken off the stems of two adult Ginkyo plants growing in the Botanical Garden of Florence.

All the material which has been studied shows the same characters, that is the frequency of uncomplete crescent-shaped wood rings, and consequently a large degree of eccentricity of the stems, depending not only upon the uncomplete wood rings, but also on the changing width of each ring.

Microscopical analysis has pointed out the presence of false rings, limited by discontinuous late wood, particularly in the female plant. This character has been observed only in a fossil wood of Ginkyo bonesii.

It has not been possible to assers how many rings or crescents are formed during one year. From dating records made on wood cores it seems that more than one ring could differentiate during one year, but the cambium shows a very irregular activity in Ginkyo. The factors which control the formation of false and uncomplete wood rings (wood crescents) are also unknown; their formation possibly depending upon environment conditions.

External factors such as water deficiency probably control cambial activity through auxin production. Larson (1964) has shown that draught causes a decrease in tracheids diameter, and the formation of false growth rings; thus the same causes could have been in action in our plants.

Noteworthy are also the data by Gungkel and Thimann (in Larson 1964) showing that auxin content increases downwards in the shoots of Ginkyo and that the apical bud has a very low auxin production, so that it seems possible that in Ginkyo the leaves supply something which the cortical tissue converts into auxin.

Lastly, the almost continuous growth activity of the cambium in Ginkyo must be pointed out, this causes a great difficulty in checking the beginning and the end of this process along the year. It is any way possible to establish the time of the highest cambial activity, which lies in June-July both in the female and in the male plants.     

Prove DI Degemmazione Nel Pesco E Loro Effetti Sulla Istogenesi della Cerchia Legnosa

Summary

Tests on disbudding and their effects on the histogenesis of the wood ring. In this work the effects of hormonic character which appear during the histogenesis of the wood ring have been studied testing disbudding effects on the peach tree.

Some observations on the consequences due to defoliation are also included.

By removal of the buds, the annual ring shows a greater depth and a more marked uniformity of structure, due to an increased frequency of the vascular elements.

By removal of the leaves, the cambial activity is completely inhibited. These results are attributed to the fact that the leaves, according to the more recent hypotheses, produce the substance which stimulates the formation of the wood elements and the differentiation of the newly formed elements.

This inactive substance, produced by the leaf, would exert its action only when the buds, towards which it is directed, transform it into its active form. The removal of the buds would eliminate the centres of diffusion of the inactive substance and also its centres of activation and concentration for the coming rest period, in view of a new vegetative cycle.

As a conseguence the circulation of the inactive substance is more marked, as it is probably activated by the cambium, and its activity lasts longer, producing in the annual ring those characters peculiar to the spring wood, that is of a season in which the circulation of this substance is at its utmost.     

THE INFLUENCE OF PRESSURE ON THE DIFFERENTIATION OF SECONDARY TISSUES

Brown, Claud L. (U. Georgia, Athens), and Karl Sax. The influence of pressure on the differentiation of secondary tissues. Amer. Jour. Bot. 49(7): 683–691. Illus. 1962.—When longitudinal bark strips of Populus trichocarpa and Pinus strobus are separated from the bole wood during early spring and maintained in a humid environment while attached to the parent tree, the cambial zone along the inner surface of the segments rapidly proliferates producing an extensive parenchymatous callus. Subsequently, a new phellogen and cambium differentiate and extend tangentially around the outer periphery of the callus pad, this resulting in the formation of a new stem-like structure. Whenever bark strips are separated from the bole wood by a layer of polyethylene plastic film and held firmly against the tree by externally applied pressure, the cambium continues to function normally, setting aside derivatives which differentiate and mature into normal, elongate xylary and phloic elements. The importance of mutual pressures and spatial relationships in controlling patterns of differentiation in secondary tissues is clearly demonstrated.     

Ulteriori Osservazioni Sulla Variabilità Del Legno Secondario in Prunus Persica Stokes

Abstract

Further observations on the variability of the secondary wood of PRUNUS PERSICA Stokes. — The length of both fibres and vessel members and the age of cambium in the trunk of a wild specimen of Prunus persica are positively correlated; no relation exists between the length of the above mentioned elements and the width of growth layers.

The relation between the intrasive growth of fibres and either age of cambium or width of growth layers has been also calculated but no significant relation has been attained.

The results have been compared with those obtained in the previous study of a trunk of a grafted Prunus persica, which are very different and quite peculiar mainly as to a decrease in length of fibres and vessel members with aging of cambium. The growing practice to which the tree may have been subjected is regarded as the possible cause of this peculiarity.     

L'evoluzione della cerchia legnosa in Arbutus Andrachnoides Link. in Firenze,dal luglio 1946 al Giugno 1947

Summary

The evolution of the wood ring in arbutus andrachnoides link, in florence (from July 1946 to June 1947).

The anatomical characters of the wood ring of the stem and of the young branch of Arbutus andrachnoides Link have been studied in Florence.

The results are the following: the cambial tissue in the stem starts dividing at the end of April and continues during the summer months, ending completely in September.

In the branch the cambium differentiates almost a month earlier, namely at the beginning of April.

In both cases the only wood ring produced is completed at the end of September. Comparing the evolution of this wood with the climatic factors it can be seen that the cambium activity starts in a period of remarkable rainfall and of regular increase of temperature and presents a remarkable activity still at the end of August.

Arbutus andrachnoides Link. is a spontaneous hybrid between A. Unedo and A. Andrachne and its distribution (in Greece and in the gréek islands) shows that A. Unedo and A. Andrachne had the possibility to overlap in this area and to produce this hybrid.     

Ritmo Dell'accrescimento Vegetativo in Olea Europaea L. Nel Clima di Firenze

Summary

The author has studied the grouth stages in the main stem of an olive-tree in Florence; the data obtained are compared with those from similar studies on trees of the same species in Bari and Camerino. In Florence, as in Camerino, the differences in habitat and climatic factors as compared with the Bari ones have noticeable effects on the cambial activity.

In Florence as in Camerino the rythmic wood production, typical of the trees growing in Bari (that is a region where the climatic conditions are more similar to those required by the species) occurs only in the autumn, while in the spring the process of wood formation is uninterrupted until summer. The period of rest in summer is very short.

The activity of the cambium, after the summer resting period, is renewed noticeably earlier in Florence than in Camerino, because of the more favourable climatic conditions, especially temperature.

In an exceptional growing period (March) an anomalous undifferentiated tissue is formed, the same that has been found in Camerino in August.     

Stem growth rhythms in trees of a tropical rainforest in Southern Brazil

Key message

We demonstrate that tropical trees growing in wet climates can have a marked seasonality in cambium activity and stem growth associated with high temperature and day length of summer.

Abstract

Monitoring the rhythm of tree growth associated with the growth rings can contribute substantially to understanding forest dynamics and the management of tropical forests. In this study, we monitored the girth increment rhythm and described the wood characteristics (anatomy of growth rings, wood specific gravity) in 10 tropical tree species (103 individuals) naturally occurring in a wet and weakly seasonal region of Atlantic Forest in southern Brazil. We aimed to verify whether tree growth dynamics are associated with climate and woody anatomy in tropical trees with contrasting ecological characteristics. We installed permanent dendrometer bands and monthly assessed the girth increment for 22 months. We collected wood samples (non-destructive method), measured wood specific gravity and prepared permanent slides to characterize the growth ring markers. We found growth rings in all species (distinct in six species); deciduous species produced more distinguishable tree rings compared with semi-deciduous and evergreen tree species. Species varied in their accumulated girth growth (in average, from 1.83 to 62.64 mm), growth rates (1–15 %), and annual radial increment (0.16–5.44 mm). Girth increment was positively related to temperature and day length in five out of ten tree species, indicating the possible effects of these climatic variables in triggering cambial activity in these species. The growth pattern varied among species and was marginally associated to the tree deciduousness. We concluded that even in wet and less seasonal climates, there can be an association in the cambium activity and stem growth with the hotter and longer days of summer months.

     

Le Plantule Della Flora Trapanese

Summary

Secondary wood growth in both a ♂ and a ♀ plant of Schinus Molle has been studied in Bari, Puglia.

The bulk of the secondary wood has been found to be made up of substitution fibres full of starch grains, which it would be more appropriate to call fusiform wood parenchyma cells (according to the « Glossary of Terms Used in Describing Woods», in Tropical Woods, N° 36, 1933).

There are no annual rings: the thickening is due to the addition of successive «growth layers», 3 or 4 per year.

The cambium does not undergo any evident resting period, neither in summer nor in winter, but only periods of suspended activity: the periods of suspended activity do not occur simultaneously in the ♂ and ♀ plants, but in different months.

Each period of cambial activity passes through the three stages of initial, maximum, and decreasing intensity and lasts for 2–3–4 months depending on the season and the sex.

Tipically the growing period starts with the deposition of new elements; next follows lignification of these same elements; during the third stage starch grains appear in the fusiform and radial parenchyma cells of the newly formed wood.

During 1952, 4 growth layers have been formed in the ♂ and 3 in the ♀ plant. In general each episode is slower and more diluted in time in the ♀ plant as compared to the ♂ one. A diversity in cambial behaviour as regards spring reawakening, between the two sexes of dioiceous plants had been already observed in Rhamnus Alaternus (De Paolis, 1949); in both species the ♂ plant appears to be more sensitive and more speedy in its reactions than the ♀ one.

The author does not know of any research on cambial activity in S. Molle carried out in Peru, the native land of this species. Comparing its cambial activity as revealed by the present researches with that of other evergreen plants spontaneous in Puglia the existence of an essential difference is demonstrated: while in S. Molle cambial activity is subcontinuous, in the Mediterranean evergreen trees and shrubs so far studied the cambium undergoes two resting periods, one in winter, and a more or less well defined one in summer. Moreover cambial activity in S. Molle can be taken as continuous if the plants of both sexes are considered, owing to their asinchronism (the same phenomenon happens in flowering times). This lack of a well defined growth cycle corresponds to a similar lack of a well defined seasonal cycle in the climate of the interandine Peruvian valleys, the original habitat of S. Molle, where the mean temperatures of the coldest months vary from 5,8° C to 11,9° C, while those of the hottest months vary from 10,3° C to 15,9° C, with yearly excursions of 4,5 to 5° C.

On the other hand the type of secondary th ckening by successive apposition of wood layers recalls closely that of a group of Mediterranean plants studied in Puglia, that is Ficus carica (Giannuoli, 1949), Olea europaea (Armenise, 1950), and Phillyrea latifolia (Maranò, 1953). In the case of these species the authors had suggested that they belonged, or were related to genera which had originated or developed in regions lacking a well defined seasonal climatic cycle. This hypothesis is confirmed by the fact that S. Molle, a recently imported tropical plant has maintained in our Mediterranean climate not only its original type of secondary thickening, but also its original growth rythm. S. Molle can be considered an experimental test of an hypothesis based so far on the interpretation of observation data.     

Primi Dati Sull'andamento Stagionale delle Temperature del Troneo di Olivo

Abstract

Temperatures recorded in a olive-tree stem in 1961–1962. — In the Botanical Garden of Bari a temperature recorder has been placed, bearing 6 electrothermometers with platinum resistences having a sensitivity of 2,4 mm/C[ddot], with a recording approximation of 0,1 C[ddot].

The olive tree under examination is a grown-up tree, which has been pruned according to the local methode, and it belongs to a local breed named « Ogliarola leccese ».

— Five thermometers have been employed as follows: 1^rst in the air, hanging from the stem, m. 1,30, high; 2^nd into the outer bark, cm, 0,5 deep; 3^rd into the cambium, cm. 1,5 deep; 4^th into the sap-wood, cm. 6 deep; 5^th into the hearth-wood, cm. 22 deep.

— The thermometers were all placed on the east side of the stem.

— The figures and the graphs of the paper show that:

a) The whole stem of the specimen under examination has a mean temperature which is higher than that of the surrounding air.

b) The outer bark gets warmer than the air, during the day-time; during the night it gives up heat outside and inside, namely towards the stem tissues, particularly to the bark-cambium-sapwood zone, and also as far as the hearth wood zone.

c) The whole living zone of the stem (bark-cambium-sapwood) generally keeps temperature values intermediate between those of the outer bark and those of the air. The temperature values vary along the year.

d) In spring the cambium is warmer than the outer bark.

e) In winter cambium and sapwood generally have the same temperature. The temperature values recorded in this season are much lower than those of the outer bark and almost the same of those of the air.

f) The behaviour of temperature in cambium and sapwood is probably ruled by biological factors.

g) The hearth-wood keeps generally warmer than the air and cooler than other outer tissues. Its thermic rhytm is almost reversed in comparison with that of the outer tissues.

Il seems that hearth wood acts as an useful heat collector and distributor towards the living outer tissues during the diurnal and seasonal temperature remissions, at least in mild climates as that of Bari.     

L'evoluzione della cerchia legnosa in Quercus Pubescens W. Ein Quercus Ilex L. nel clima di Firenze

Summary

The evolution of the wood ring in Quercus pubescens W. and in Quercus Ilex L. in Florence (from June 1946 to June 1947).

The present study deals with the anatomical characters of the wood ring of Q. pubescens and of Q. Ilex. In both the specimens the wood of the stem and of the young branch has been investigated.

In both plants studied the cambial tissue of the stem starts dividing at the end of April, reaching its maximum activity from May to June.

On the contrary the cambium of the branch differentiates in Q. pubescens a month earlier (18 March-18 April) than in Q. Ilex (18 April-18 May). While in the branch of Q. Ilex a false ring can be seen corresponding to the autumn months, nothing of the kind is found in the branch of Q. pubescens; though it presents a false ring in the stem.

It is difficult to date clearly the period when the cambium stops its activity, but probably it happens at the end of August in the samples of the stem.

The leaf buds of Q. pubescens and of Q. Ilex open during April-May and the young branch is completely developed at the end of June. In both oaks some buds open in autumn, but the small branches are prevented to develop because of the cold.

No comparison can be made between the opening of the buds and the beginning of the cambial activity in the stem and in the branch.

Considering the evolution of these woods and their relationship to climatic factors, we can see that the cambial activity starts during a period of remarkable rainfall and of regular increase of temperature, and stops almost completely at the end of July, when temperature and dryness reach their highest values.

The autumn rainfall would favour again a cambial activity, but the values of the temperature, regularly decreasing, do not allow it.     

Growth dynamics and potential for cross-dating and multi-century climate reconstruction of Podocarpus falcatus in Ethiopia

Podocarpus falcatus is an indigenous evergreen conifer species of tropical mountain forests in southeastern Ethiopia, showing potential tree ages of around 500 years. To study the influence of seasonal climate on the growth pattern of P. falcatus, we combined high-resolution electronic dendrometer measurements with wood anatomical investigations of microcores from the outermost stem parts collected in monthly intervals. At any time of the year sufficient rain events are able to cause cambial activity in P. falcatus. This permanent growing readiness leads to irregular wood formation with the formation of intra-annual density fluctuations and missing rings. Wood anatomical studies of microcores collected around the circumference of a mature P. falcatus revealed locally different activity status of the cambium on different lobes of the stem. Tree-ring width measurements of stem disks resulted in tentative tree ages that were confirmed by radiocarbon dating of selected wood samples. Although our efforts to cross-date ring-width series from several stem disks were not successful, further sampling in areas with different rainfall regimes, additional radiocarbon dating and measurements of stable isotopes hopefully would enable the establishment of a multi-century-long tree-ring series for climate reconstruction.     

Seasonal cambium activity in the subtropical rain forest tree Araucaria angustifolia

Information on the timing and dynamics of tree ring formation is essential to assess the seasonal behavior of secondary wood growth and its associated environmental influences. Araucaria angustifolia is a dominant species in highland pluvial ecosystems of southeastern South America. Previous investigations indicated that their growth rings are formed annually, but no information exists about the timing of growth ring formation and the environmental triggers influencing cambium activity. In this paper we examine inter- and intra-annual cambial activity in A. angustifolia, through anatomical and dendrochronological evidence at two study sites, and model the relationships between regional climate variation and intra-annual tree ring formation. The results confirm the annual growth ring formation in A. angustifolia and indicate that its growth season extends from October to April. Day length and temperature were the main environmental factors influencing the seasonal cambium activity. Our results evidence the dendrochronological potential of A. angustifolia for ecological and climatological studies in southeastern South America.