scholarly journals Why should trees have natural root grafts?

2011 ◽  
Vol 31 (6) ◽  
pp. 575-578 ◽  
Author(s):  
S. Lev-Yadun
Keyword(s):  
Root Grafts

scholarly journals Presence of Xylella fastidiosa in Sweet Orange Fruit and Seeds and Its Transmission to Seedlings

2003 ◽  
Vol 93 (8) ◽  
pp. 953-958 ◽  
Author(s):  
W.-B. Li ◽  
W. D. Pria ◽  
P. M. Lacava ◽  
X. Qin ◽  
J. S. Hartung
Keyword(s):  
Vascular System ◽  
Sweet Orange ◽  
Xylella Fastidiosa ◽  
Germination Rate ◽  
Citrus Fruit ◽  
Vascular Bundles ◽  
Specific Amplification ◽  
Root Grafts ◽  
Citrus Seeds

Xylella fastidiosa, a xylem-limited bacterium, causes several economically important diseases in North, Central, and South America. These diseases are transmitted by sharpshooter insects, contaminated budwood, and natural root-grafts. X. fastidiosa extensively colonizes the xylem vessels of susceptible plants. Citrus fruit have a well-developed vascular system, which is continuous with the vascular system of the plant. Citrus seeds develop very prominent vascular bundles, which are attached through ovular and seed bundles to the xylem system of the fruit. Sweet orange (Citrus sinensis) fruit of cvs. Pera, Natal, and Valencia with characteristic symptoms of citrus variegated chlorosis disease were collected for analysis. X. fastidiosa was detected by polymerase chain reaction (PCR) in all main fruit vascular bundles, as well as in the seed and in dissected seed parts. No visual abnormalities were observed in seeds infected with the bacterium. However, the embryos of the infected seeds weighed 25% less than those of healthy seeds, and their germination rate was lower than uninfected seeds. There were about 2,500 cells of X. fastidiosa per infected seed of sweet orange, as quantified using real-time PCR techniques. The identification of X. fastidiosa in the infected seeds was confirmed by cloning and sequencing the specific amplification product, obtained by standard PCR with specific primers. X. fastidiosa was also detected in and recovered from seedlings by isolation in vitro. Our results show that X. fastidiosa can infect and colonize fruit tissues including the seed. We also have shown that X. fastidiosa can be transmitted from seeds to seedlings of sweet orange. To our knowledge, this is the first report of the presence of X. fastidiosa in seeds and its transmission to seedlings.

scholarly journals Nontarget Tree Mortality after Tree-of-Heaven (Ailanthus altissima) Injection with Imazapyr

2008 ◽  
Vol 25 (2) ◽  
pp. 66-72 ◽  
Author(s):  
Kevin Lewis ◽  
Brian McCarthy
Keyword(s):  
Mycorrhizal Fungi ◽  
Tree Mortality ◽  
Root Exudation ◽  
Ailanthus Altissima ◽  
Tree Of Heaven ◽  
Increased Risk ◽  
Vegetation Heterogeneity ◽  
Nontarget Species ◽  
Root Grafts ◽  
Injection Risk

Abstract Tree-of-heaven (Ailanthus altissima Miller [Swingle]) can be managed easily with herbicide injection. However, the potential herbicide translocation to neighboring trees must be evaluated before widespread recommendations for herbicide injections. We assessed the nontargettranslocation of imazapyr (Arsenal), an herbicide commonly used to manage woody vegetation in forests, from injected tree-of-heaven to neighboring noninjected stems. Targeted imazapyr injections not only killed all injected tree-of-heaven, but also killed 17.5% of neighboring (within 3 m) noninjected tree-of-heaven and eight other tree species 62 weeks after treatment. Nontarget mortality from herbicide translocation decreased as the distance from injected tree-of-heaven increased (up to 3 m) and as stem diameter of noninjected plants increased. The plausible modes ofinter- and intraspecific herbicide translocation include root grafts, mutually shared mycorrhizal fungi, root exudation and absorption, and/or leaf senescence. Because tree-of-heaven is clonal, patch size and vegetation heterogeneity will be an important determinant of herbicide injectionprotocols. In forest environments with many small patches (i.e., high edge to interior ratio) or mixed species stands, nontarget hardwoods are at an increased risk of mortality. In isolated large patches (with lower edge to interior ratio) or dense monospecific clones, injection risk to nontarget species will be relatively low.

Frequency of root grafting in naturally and artificially regenerated stands of Pinus banksiana: influence of site characteristics

2010 ◽  
Vol 40 (5) ◽  
pp. 861-871 ◽  
Author(s):  
Emilie Tarroux ◽  
Annie DesRochers
Keyword(s):  
Pinus Banksiana ◽  
Sandy Soils ◽  
Stand Density ◽  
Stand Development ◽  
Site Characteristics ◽  
Root Grafting ◽  
Naturally Regenerated Stands ◽  
Root Grafts ◽  
High Level ◽  
Western Boreal Forest

We investigated the frequency of root grafting in naturally and artificially regenerated stands of jack pine ( Pinus banksiana Lamb.) in the western boreal forest of Quebec, Canada. Twelve 30–60 m2 plots were hydraulically excavated to determine effects of site characteristics on frequency and timing of root grafting. Naturally regenerated stands had grafted tree percentages similar to artificially regenerated stands (21%–71% across plots) but greater numbers of root grafts per tree (naturally regenerated, 0.73 graft·tree–1; artificially regenerated, 0.52 graft·tree–1). Mean percentages of grafted trees, number of grafts per tree, and the speed of graft formation were greater in sandy soils (61%, 0.71 graft·tree–1 and 2.43 years, respectively) compared with clay soils (44%, 0.54 graft·tree–1 and 2.97 years, respectively). Proximity of trees was a better predictor of root grafting than stand density, despite many root grafts being found with distant trees (>2 m) in artificially regenerated stands. Our results suggested that root grafts form early in stand development. Even if trees are initially separate entities, this relatively high level of root grafting produces stands where trees are extensively interconnected.

Root Grafts and their Silvicultural Implications

1972 ◽  
Vol 2 (2) ◽  
pp. 111-120 ◽  
Author(s):  
S. Eis
Keyword(s):  
Root System ◽  
Vancouver Island ◽  
Douglas Fir ◽  
Western Hemlock ◽  
Slow Recovery ◽  
Red Cedar ◽  
Western Red Cedar ◽  
Root Grafts

Many trees in stands of Douglas fir, western hemlock and western red cedar on Vancouver Island were joined by functional grafts. In a partially cut stand, 45% of the stumps showed evidence of continued growth and half of these (23%) were still growing vigorously more than 22 years after logging. On experimentally detopped trees, growth extended several meters up the bole. Dominant trees usually supported the growth of the root system and lower boles of grafted suppressed trees.Translocation through grafts may partially explain the frequent stagnation and slow recovery of stands after thinning from above, and may be involved in the usually rapid increase of growth after thinning from below. It is probably a contributing factor in establishing dominance and determining mortality in overtopped trees. In species that graft freely, the use of silvicides in spacing and thinning treatments should be restricted to young stands before grafts are established.

Ceratocystis ulmi. [Descriptions of Fungi and Bacteria].

1973 ◽  
Author(s):  
C. Booth
Keyword(s):  
Geographical Distribution ◽  
Bark Beetles ◽  
Dutch Elm Disease ◽  
Airborne Spores ◽  
Eastern Canada ◽  
Eastern Usa ◽  
Scolytus Scolytus ◽  
Root Grafts ◽  
Hylurgopinus Rufipes ◽  
Marked Resistance

Abstract A description is provided for Ceratocystis ulmi. Information is included on the disease caused by the organism, its transmission, geographical distribution, and hosts. HOSTS: Ulmus spp., Zelkova serrara; U. glabra and U. americana are highly susceptible, U. procera is susceptible, while Asian elms, U. parvifolia, U. pumila and U. pumila pennato-ramosa, have marked resistance. Zelkova serrata is highly susceptible; the reactions of other species of Zelkova are not known. DISEASE: Dutch Elm Disease. GEOGRAPHICAL DISTRIBUTION: Europe (throughout, to a northern limit in central Scotland, central Norway, central Sweden. Absent from north Russia). N. America (eastern Canada, central and eastern USA) (CMI Map 36, ed. 4, 1970). TRANSMISSION: By the bark beetles Scolytus scolytus, S. multistriatus and (in N. America) by Hylurgopinus rufipes. The fungus fruits in the larval galleries and spores are carried internally and externally to young shoots where beetles emerge and migrate. Infection of the vessels, which leads to the disease, takes place during the period before breeding, when the beetles feed, cutting grooves and boring in the thin bark of twigs. Transmission by root grafts is known (15, 266) and direct infection by airborne spores is theoretically possible but does not take place under natural conditions.

Effects of a native forest pathogen, Phellinusweirii, on Douglas-fir forest composition in western Oregon

1993 ◽  
Vol 23 (12) ◽  
pp. 2473-2480 ◽  
Author(s):  
Jenny C. Holah ◽  
Mark V. Wilson ◽  
Everett M. Hansen
Keyword(s):  
Tree Mortality ◽  
Vascular Plant ◽  
Douglas Fir ◽  
Forest Composition ◽  
Native Forest ◽  
Forest Pathogen ◽  
Vascular Plant Diversity ◽  
Center Edge ◽  
Ordination Techniques ◽  
Root Grafts

The fungal pathogen Phellinusweirii (Murrill) Gilbertson (Family: Hymenochaetaceae) causes extensive rot in the roots and bole of Douglas-fir (Pseudotsugamenziesii (Mirb.) Franco) and true firs, eventually leading to tree mortality. The native pathogen spreads slowly via root grafts and root contacts between conifers, leaving behind areas of tree mortality commonly called infection centers. This study determines (i) whether the slow, systematic removal of the Douglas-fir overstory by P. weirii changes the community composition of old-growth and mature forests, (ii) if composition is significantly affected, to what degree P. weirii influences the composition, (iii) what effects the disease has on individual populations, and (iv) whether vascular plant diversity is affected by disease presence. The herb, shrub, and tree strata were randomly sampled within and adjacent to six P. weirii infection centers located in the low-elevation Cascade and Coast ranges of western Oregon. Statistically significant (P ≤ 0.05) differences in species composition between infected and adjacent noninfected forest were found across all sites. Ordination techniques showed that the distance of vegetation to the infection center edge was a major factor underlying the forest community's structure. The average cover of all herbaceous species was higher inside infection centers as compared with outside, for all locations, though statistically significant at only two sites. In general, species differed in their responses to disease presence. Changes in diversity due to the presence of the root rot were statistically significant in three of the six cases (P ≤ 0.05) but the patterns of change differed from site to site. The removal of Douglas-fir overstory has strong effects on the plant community, but the specific patterns depend on the species and site involved.

scholarly journals Hurricane Hugo: damage to a tropical rain forest in Puerto Rico

1992 ◽  
Vol 8 (01) ◽  
pp. 47-55 ◽  
Author(s):  
Khadga Basnet ◽  
Gene E. Likens ◽  
F. N. Scatena ◽  
Ariel E. Lugo
Keyword(s):  
Puerto Rico ◽  
Rain Forest ◽  
Tropical Rain Forest ◽  
Severe Damage ◽  
Luquillo Experimental Forest ◽  
Size Classes ◽  
The North ◽  
Large Trees ◽  
Root Grafts ◽  
Hurricane Hugo

ABSTRACTHurricane Hugo of September 1989 caused severe damage to the rain forest in the north-rust corner of Puerto Rico. We assessed the severity of damage distributed in space, species, and size-classes of trees in the Bisley Watersheds of the Luquillo Experimental Forest. We analyzed pie- and post-hurricane data for vegetation from transects established in 1987 and 1988. The severity of damage was significantly greater in valleys than on ridges and slopes. All the species exceptDacryodes excelsa, Sloanea berteriana, andGuarea guidoniashowed 100% severe damage. Large trees (> 70 cm DBH) were highly susceptible to hurricane damage, but there was no clear pattern in the small size-classes.D. excelsa(tabonuco) was the most resistant to damage by the hurricane. Tabonuco which has extensive root-grafts and root anchorage to bedrock and subsurficial rocks, apparently can survive frequent hurricanes and continue as a dominant species in this montane tropical rain forest. The high frequency of hurricanes, which can override other ecological and topographic factors, may largely determine the overall spatial pattern of species in this rain forest.

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