Localized cooling of stems induces latewood formation and cambial dormancy during seasons of active cambium in conifers

Background and Aims In temperate regions, trees undergo annual cycles of cambial growth, with periods of cambial activity and dormancy. Environmental factors might regulate the cambial growth, as well as the development of cambial derivatives. We investigated the effects of low temperature by localized cooling on cambial activity and latewood formation in two conifers, Chamaecyparis obtusa and Cryptomeria japonica.Methods A plastic rubber tube that contained cooled water was wrapped around a 30-cm-wide portion of the main stem of Chamaecyparis obtusa and Cryptomeria japonica trees during seasons of active cambium. Small blocks were collected from both cooled and non-cooled control portions of the stems for sequential observations of cambial activity and for anatomical measurements of cell morphology by light microscopy and image analysis.Key Results The effect of localized cooling was first observed on differentiating tracheids. Tracheids narrow in diameter and with significantly decreased cambial activity were evident 5 weeks after the start of cooling in these stems. Eight weeks after the start of cooling, tracheids with clearly diminished diameters and thickened cell walls were observed in these stems. Thus, localized low temperature induced narrow diameters and obvious thickening of secondary cell walls of tracheids, which were identified as latewood tracheids. Two months after the cessation of cooling, a false annual ring was observed and cambium became active again and produced new tracheids. In Cryptomeria japonica, cambial activity ceased earlier in locally cooled portions of stems than in non-cooled stems, indicating that the cambium had entered dormancy sooner in the cooled stems.Conclusions Artificial cooling of stems induced latewood formation and cessation of cambial activity, indicating that cambium and its derivatives can respond directly to changes in temperature. A decrease in the temperature of the stem is a critical factor in the control of cambial activity and xylem differentiation in trees.     

Comparative anatomy and ultrastructure of active and dormant vascular cambium in rhizome ofBotrychium ternatum

Vascular cambium ofBotrychium ternatum rhizome varied according to age, position and season was studied by light and electron microscopy. Cambium at the 6th internode (6-year-old cambium) had the greatest number of active cambial cells in August and September, thus it was in the most active stage. The active cells were characterized by the presence of a large vacuole, few storage materials such as starch grains within plastids or lipid droplets, a thin tangential wall; and various cell organelles in the thin peripheral layer of cytoplasm. When the 6-year-old cambium reached its dormant season after November, the dormant cells were filled with numerous storage materials and had few cell organelles. Our observations suggested that the initiation and cessation of cambial activity may be correlated with the annual life cycle of this plant: the vegetative and reproductive leaves began to emerge in June and July, respectively, and the sporophyll withered in November after the spore dispersal. Most cambial cells at the 10th internode, which remained in a dormant state throughout the year, were filled with numerous storage materials. Our results indicated that the activity of vascular cambium in the 10th internode was determinate.     

Seasonality and growth rings in lianas of Bignoniaceae

Lianas are one of the most important components of tropical forest, and yet one of the most poorly known organisms. Therefore, our paper addresses questions on the environmental and developmental aspects that influence the growth of lianas of Bignoniaceae, tribe Bignonieae. In order to better understand their growth, we studied the stem anatomy, seasonality of formation and differentiation of secondary tissues, and the influence of the cambial variant in xylem development on a selected species: Tynanthus cognatus. Afterwards, we compared the results found in T. cognatus with 31 other species of Bignonieae to identify general patterns of growth in lianas of this tribe. We found that cambial activity starts toward the end of the rainy season and onset of the dry season, in contrast to what is known for tropical trees and shrubs. Moreover, their pattern of xylem formation and differentiation is strongly influenced by the presence of massive wedges of phloem produced by a variant cambium. Thus, the variant cambium is the first to commence its activity and only subsequently does cambial activity progress towards the center of the regular region, leading to the formation of confluent growth rings. In summary, we conclude that: the cambium responds to environmental changes; the xylem growth rings are annual and produced in a brief period of about 2 months, something that may explain why lianas possess narrow stems; and furthermore, phloem wedges greatly influence cambial activity.     

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.     

Dendroecological investigations on Swietenia macrophylla King and Cedrela odorata L. (Meliaceae) in the central Amazon

The width of the increment zones in the xylem of Swietenia macrophylla King and Cedrela odorata L. was investigated by dendroecological methods in a primary forest near Aripuanã, Mato Grosso, Brazil (10°09′S, 59°26′W). The annual period of cambial cell division and its intra-annual variation were determined by dendrometer measurements of 30 trees of each species. Tree-ring width chronologies for Swietenia and Cedrela were developed from cross-dated increment curves of 33 out of 47 Swietenia and 51 out of 64 Cedrela trees. Simple correlations were computed between the radial growth increment and monthly precipitation for the period 1890–2000. In Swietenia, cambium activity occurred throughout almost the whole year, but in Cedrela it was restricted to the rainy period from September of the previous year to June of the current year. Tree-rings were formed annually in the juvenile and adult wood of Cedrela, while in Swietenia the annual formation of tree-rings was restricted to the adult wood. Consequently the age of the Swietenia trees could be dated by the tree-rings in good approximation, while age dating of the Cedrela trees was exact. Correlation analyses revealed a significant relationship between the precipitation at the beginning and at the end of the growth season and the width of the increment zones in the adult xylem of Swietenia. In contrast, the width of the growth increment in the xylem of Cedrela was significantly correlated with the precipitation in March and May of the previous growth period.     

The Annual Rhythm of Activity of the Lateral Meristems (Cambium and Phellogen) in Cupressus sempervirens L

The annual rhythm of cambial activity in Cupressus sempervirensseems to be endogenous and fits well the Mediterranean climaticrhythm. Under outdoor conditions the cambium begins its activitytowards the autumn when temperatures drop and water is lesslimiting. The cambium continues to be active during the mildMediterranean winter and enters dormancy towards the beginningof the dry summer. A constant supply of water is not enoughto avoid cambial dormancy but may result in earlier onset anda prolonged period of activity. Relationships between xylemand phloem production, between shoot and root, and between cambialand phellogen activity are discussed. Cupressus sempervirens L., cypress, cambium, phellogen, annual rhythm, wood production     

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.     

Seasonal development of secondary xylem and phloem in <Emphasis Type="Italic">Schizolobium parahyba</Emphasis> (Vell.) Blake (Leguminosae: Caesalpinioideae)

The cambial activity and periodicity of secondary xylem and phloem formation have been less studied in tropical tree species than in temperate ones. This paper describes the relationship between seasonal cambial activity, xylem and phloem development, and phenology in Schizolobium parahyba, a fast growing semideciduous seasonal forest tree from southeastern Brazil. From 2002 to 2003, wood samples were collected periodically and phenology and climate were recorded monthly in the same period. S. parahyba forms annual growth increments in wood, delimited by narrow initial parenchyma bands. The reduction of the cambial activity to a minimum correlates to the dry season and leaf fall. The higher cambial activity correlates to the wet season and the presence of mature leaves. In phloem, a larger conductive region was observed in the wet season, when the trees were in full foliage. The secondary phloem did not exhibit any incremental zone marker; however, we found that the axial parenchyma tends to form irregular bands.     

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.     

EFFECT OF ISOLATION OF BARK ON CAMBIAL ACTIVITY AND DEVELOPMENT OF XYLEM AND PHLOEM IN TREMBLING ASPEN

Circular patches of bark were surgically isolated on the sides of trembling aspen (Populus tremuloides Michx.) trees at breast height at various times during the dormant and growing seasons. Subsequently, samples of wood and attached bark were taken from isolated and control sites to determine the effects of isolation of the bark on cambial activity and xylem and phloem development. In control trees cambial activity and xylem and phloem development occurred normally. Isolation of bark during the dormant season (in November, February, or March) did not prevent initiation of cambial activity and of phloem differentiation in spring but continued normal cambial activity and phloem developmented were prevent. Xylem differentiation was essentially prevented by isolation of tissues during the dormant season. The ultimate effect of isolation of the bark on the cambium, either during the dormant season or during the growing season, was subdivision of all fusiform cambial cells into strands of parenchymatous elements; the ultimate effect on the newly formed phloem was early death of the sieve elements. The most conspicuous effect of isolation of the bark after xylem differentiation had begun was the curtailment of secondary wall formation. Shortening of cells of the cambial region was reflected in the length of the vessel members which differentiated from such cells. These results indicate that normal cambial activity and xylem and phloem development require a supply of currently translocated regulatory substances from the shoots.     

Seasonal dynamics of wood formation in Oriental beech (Fagus orientalis Lipsky) along an altitudinal gradient in the Hyrcanian forest, Iran

The cambium dynamics and wood formation of Oriental beech (Fagus orientalis Lipsky) was investigated during the 2008 growing season in the Nowshahr Hyrcanian forest, Iran (36°N, 51°E). Three study sites were selected along an altitudinal gradient (650, 1,100 and 1,600 m a.s.l.), and cambial activity rates of cell formation and cell maturation were studied on micro-cores collected in intervals of 10–20 days. The cambium reactivation of the low-altitude (L) and mid-altitude (M) trees occurred contemporaneously in late March, and also the consecutive phases of cell differentiation took place almost at the same time; however, the entry into cambial dormancy varied considerably from late August to mid-November. Due to lower temperature, the upper-altitude (U) trees showed a 10-day delay in their cambium reactivation, an earlier entry into cambium dormancy (mid-September) and a slower growth rate resulting in narrower tree rings. Despite these differences, the daily increment rates of the trees at all sites reached maximum values coincidently in the early June. Since the photoperiod is the only common external factor among different sites, it is concluded that the timing of the highest growth rate is controlled by the photoperiod.     

Variations in the Lengths of Fusiform Cambial Cells and Vessel Elements in Kalopanax pictus

Samples of a mature specimen of Kalopanax pictus, a ring-poroushardwood, were studied to compare the respective lengths offusiform cambial cells and vessel elements in the stem. Thelengths of dormant and reactivated fusiform cambial cells weremeasured with a confocal laser scanning microscope in tissuethat had been macerated by digestion with pectinase and in thicktangential sections. The lengths of early wood and late woodvessel elements were measured in tissues that had been maceratedby Franklin's method. The vessel elements and fusiform cambialcells varied considerably in length within individual samples.The mean length of early wood vessel elements corresponded tothat of fusiform cells in the dormant cambium but not in thereactivated cambium. Significant differences were observed betweenthe mean lengths of dormant and reactivated fusiform cambialcells, between those of reactivated fusiform cambial cells andearly wood vessel elements, between those of reactivated fusiformcambial cells and late wood vessel elements, and between thoseof early wood and late wood vessel elements. The frequency distributionsof lengths of cambial cells were bimodal and differed from thoseof vessel elements, which more closely resembled a normal distribution.The proportion of shorter lengths was higher in the reactivatedcambium than in the dormant cambium, the early wood and thelate wood vessel elements. Our results do not suppot the hypothesisthat the lengths of early wood vessel elements in ring-poroushardwoods change during differentiation. The similar rangesof recorded lengths suggest that short and long vessel elementsmight be derived directly from short and long cambial cells,respectively. Copyright 1999 Annals of Botany Company Kalopanax pictus, cambium, vessel element, confocal laser scanning microscopy, maceration, cell length.     

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.     

Gas Chromatography-Mass Spectroscopy Identification of 1-Aminocyclopropane-1-carboxylic Acid in Compressionwood Vascular Cambium of Pinus contorta Dougl

Following cation and anion exchange chromatography, 1-aminocyclopropane-1-carboxylic acid (ACC) was converted to the 2,4-dinitrophenyl derivative and then purified by high-performance liquid chromatography (HPLC). After three HPLC steps, endogenous ACC was identified by GCMS in the vascular cambium on the lower side of Pinus contorta Dougl. ssp. latifolia branches in association with compressionwood differentiation, but ACC was not detected in the opposite wood cambial region on the upper sides of the same branches.

The possibility that ACC and ethylene have physiological roles in cambial activity and compressionwood tracheid differentiation is discussed.

     

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.     

7. The role of plant growth regulators in forest tree cambial growth

The regulation of cell-division activity in the vascular cambium and of secondary xylem and phloem development is reviewed for temperate-zone tree species in relation to auxins, gibberellins, abscisic acid, cytokinins, and ethylene. Representatives of the first four of these PGR classes (IAA, GA₁, GA₄, GA₇, GA₉, GA₂₀, ABA, Z, ZR, DCA) have been identified conclusively by mass spectrometry in the cambial region in some Pinaceae, but not in any hardwood species. Endogenous ethylene has yet to be definitively characterized in this region in any species. Evidence concerning the source and metabolism of cambial PGRs is scanty and inconclusive for both conifers and hardwoods.Most cambial PGR research has focused on IAA. Much evidence indicates that this PGR is transported primarily in the cambial region at a rate of about 1 cm h^–1, and that the transport is basipetally polar. GC-MS measurements have established that endogenous IAA levels in the cambial region of Pinaceae are highest during earlywood development, and that cambial IAA levels may be considerably lower in hardwoods than in conifers. IAA appears to be involved in the control of cambial growth in conifers and hardwoods in at least three specific ways, viz. maintenance of the elongated form of fusiform cambial cells, promotion of radial expansion in primary walls of cambial derivatives, and regulation of reaction wood formation. In addition, it is well established that exogenous IAA promotes vessel development in hardwoods. In both conifers and hardwoods, exogenous IAA stimulates cambial growth in 1-year-old shoots treated late in the dormant period or after the start of the cambial growing period. However, exogenous IAA has little effect on cambia that are older or are in what is hypothesized to be the resting stage of dormancy. Thus it is uncertain whether IAA is directly involved in the control of cambial growth, or acts indirectly through a process such as hormone-directed transport.It is not yet clear if gibberellins play a role in the control of cambial growth in conifers. However, in hardwoods, there is evidence that they inhibit vessel development and act synergistically with IAA in promoting cambial activity and fiber elongation. In both conifers and hardwoods, foliar sprays of gibberellins increase the accumulation of biomass above-ground, particularly in the main axis, while decreasing it in the roots.There are as yet no definite conclusions to be drawn concerning the involvement of ABA, cytokinins, and ethylene in the regulation of cambial growth in conifers or hardwoods. In conifers, ABA may antagonize the promotory effect of IAA on cambial cell division and tracheid radial expansion under conditions of water stress, but high endogenous ABA levels do not appear to be associated with the formation of latewood or the onset of cambial dormancy. Some evidence suggests that exogenous cytokinins enhance the promotory effect of IAA on cambial growth, particularly ray formation, in both hardwoods and conifers. However, exogenous cytokinins, by themselves, appear to be ineffective. In hardwoods, ethylene-generating compounds satisfy the chilling requirement of the dormant cambium and promote the formation of wood having an apparently greater content of lignin and extractives. Ethylene-generators also affect wood development in conifers and accelerate cambial growth at the application site in both hardwoods and conifers.     

Periodicity and environmental drivers of apical and lateral growth in a Cerrado woody species

Key message

Apical and lateral growth are seasonal in a Cerrado species, and these events are related to each other and linked with climatic and environmental features.

Abstract

In the Cerrado, a tropical ecosystem with seasonal rainfall, we investigated the timing of leaf production and cambial activity, and checked whether these features are related to each other and with climatic and environmental factors. Between September 2011 and December 2012, sampling of main stem and vegetative phenological observations of Kielmeyera grandiflora (Wawra) Saddi (Calophyllaceae) were done monthly to assess seasonality in leaf production and cambial activity, and to compare these features with each other. To check the relationship of bud opening and the onset of cambial activity with climatic and environmental features, the average temperature and day length, and the precipitation sum in a time window ranging from 1 to 30 days before the occurrence of these events were recorded, and the coefficient of variation was calculated. Leaf production and cambial activity were seasonal. Bud opening occurred in September 2011 and August 2012, during the dry season. The onset of cambial activity occurred in October both in 2011 and 2012, 1–2 months after bud opening, at the beginning of the rainy season. The cambium was dormant in May, during the rainy season. Photoperiod and temperature showed low coefficients of variation in the time window before bud opening and onset of cambial activity, while rainfall presented a high coefficient of variation. Thus, both apical and lateral growth are seasonal events in Cerrado species, and are related to each other. A set of climatic and environmental features is related with seasonal growth, among which photoperiod and temperature may be important in the regulation of these events.

     

Auxin Stimulation of Cambial Activity in Pinus silvestris I. The Differential Cambial Response

Isolated stem segments of Pinus silvestris L. produce new xylem in sterile culture for 5 weeks if sucrose and IAA are present in the medium. The response of cambium varies in the course of the season and along the tree stem. The cambium is more sensitive in spring and in the stem portion closer to tree apex than later in the season and closer to the stem base. Spring initiation of cambial activity in adult pine trees under natural conditions could not be correlated with any consistent concentration gradient of natural auxin extracted from the cambial region. Thus, the relation between concentration of auxin and the activity of cambium is complex and involves changes of cambial responsivity. Interaction with gibberellic acid or kinetin and changing concentration of sucrose were studied during the season, but none of these substances alone appeared to be responsible for the observed variation in cambial response to auxin.