Production Of Adventitious Roots Research Articles

Histology of witches' brooms on Betula pubescens

AbstractWitches' brooms caused by Taphrina betulina on Betula pubescens formed from the development of large numbers of axillary shoots on infected buds. Broom shoots showed vigorous growth during the first season, but died in the second or third year after initiation. Occasional adventitious root production was noted at the base of broom shoots. Cortex and secondary phloem tissues of the central gall‐like structure of the brooms expanded. The bark of infected material lacked brachysclereids, and tangential ray parenchyma of the secondary phloem were also absent. Numerous shoot bases and aborted axillary buds were present within the bark. Abundant starch granules were present, especially in the phellogen and phelloderm layers. Distortion of the internal lignified tissues was due to the presence of multiple vascular connections from the proliferation of shoots on the broom.

Effect of ?-naphthaleneacetic acid and sucrose levels on the development of cultured embryos of coconut

Mature coconut embryos were germinated in a modified Murashige and Skoog medium and then cultured on BMY3 medium incorporating sucrose in the range of 4 to 8%. α-Naphthaleneacetic acid (NAA) was added into the medium at concentrations ranging from 0 to 800 μM for periods of 4 to 24 weeks. Application of NAA for 4 weeks stimulated shoot growth, whereas application periods greater than 4 weeks had no significant effect. NAA in the range of 100–300 μM stimulated elongation of the primary root and the optimum concentration increased with increases in sucrose levels. Production of adventitious roots was stimulated by the addition of NAA with levels of 200 μM and above being the most effective. Increasing the sucrose concentration from 4% through to 8% stimulated root elongation in the absence of NAA and inhibited shoot growth whether NAA was present or absent.

Effects of root hypoxia and a low P supply on relative growth, carbon dioxide exchange rates and carbon partitioning in Pinus serotina seedlings

The present study was conducted to determine how 10 weeks of root hypoxia and a low P supply altered relative growth, and carbon acquisition and partitioning in a moderately flood tolerant pine. Pond pine (Pinus serotina Michx.) seedlings were grown in continuously flowing solution culture at 5 or 100 μM P, under aerobic or hypoxic solution conditions. Staggered harvests were used to ascertain changes in biomass allocation and relative growth over time. Carbon dioxide exchange rates (CER) were determined by infrared gas analysis, and needles were analyzed for inorganic P (Pi), sucrose, reducing sugars and starch. Although aeration treatment had no significant effect on shoot dry weight or shoot ontogeny, root dry weight of hypoxic seedlings was significantly lower than that of aerobic seedliings after 8 weeks, regardless of the P treatment. Mean relative growth rates (RGR) of roots in the high P treatment initially decreased under hypoxia, but recovered by the sixth week with the production of adventitious roots. Two weeks of hypoxic growth conditions decreased CER and stomatal conductances of seedlings in the high P treatment by more than 30% relative to their aerobic counterparts. Stomatal closure was not accompanied by a decrease in intracellular CO2, but was accompanied by an increase in starch accumulation. Recoveries of CER, stomatal conductance and carbohydrate metabolism coincided with the recovery of root growth. Low P growth conditions did not significantly affect shoot or root dry weight until the sixth week of treatment. However, differences in seedling RGR, particularly needle RGR, were discernable during the first 2 weeks. Low P treatment effects on CER paralleled changes in needle RGR, with needle RGR more affected than CER. After 6 weeks, CER of aerobically grown seedlings in the low P treatment were only 15% lower than CER of seedlings in the high P treatment, despite a 31% and 75% reduction in needle RGR and Pi concentrations, respectively. Increased starch concentrations of recently expanded needles at this time were probably a result of diminished growth. The inhibitory effect of a low P supply on shoot growth, more specifically on needle expansion and emergence of new fascicular needles, probably limited net carbon fixed per plant more than any direct effect of low P on CER per se.

Hurricane Damage to a Flood Plain Forest in the Luquillo Mountains of Puerto Rico

Hurricane Hugo caused low to moderate damage to a flood plain forest that was partially protected by its topographic position. Treefalls and the location of damage suggested N to NW wind direction during the storm. Thirty percent of the trees, or 693 trees/ha, had some damage and 84 percent of the damage was to the canopy. Most of the damage to trees was caused by direct wind impact (83%) as opposed to secondary effects (16%). Over 80 percent of the snapped, leaning, and uprooted trees were dicotyledonous. Tree mortality was only 1 percent, and most of the damage to the sierra palm Prestoea montana (R. Grah.) Nichols was loss of leaves. Rapid refoliation, epicormic branching, adventitious root production, resprouting, and regeneration from seed in open areas were observed nine months after the event. Ten percent of the aboveground biomass and 12-16 percent of the nutrient stocks (N, P, K, Ca, Mg) were transferred to the forest floor, mostly in the form of woody biomass and nutrient-rich leaves. Palm leaves were the dominant leaf component of necromass. Instantaneous in situ fine and coarse necromass production was 10 and 9.2 Mg/ha, respectively. Net changes in aboveground mass, N, P, K, Ca, and Mg (in percent of prehurricane value) were 8, 3, 0, 3, 12, and 1, respectively, in spite of a high rate of loss by export. The source of additional mass and nutrients were boles from upland forests that fell into and remained inside the flood plain.

Relationship between spring vigor and the presence of adventitious roots in established stands of red clover (Trifolium pratense L.)

Two experiments were undertaken to investigate the relationship between the presence of adventitious roots growing from the crown of red clover plants and the spring vigor of those plants. Experiment 1 was conducted in the springs of 1988 and 1989 in commercial stands of red clover-timothy mixtures entering their third year. Two hundred and thirty-seven plants were visually rated for spring vigor and degree of adventitious rooting using an ordinal scale. Experiment 2 was carried out on a research plot entering its fourth year and consisting of mixtures of red clover and timothy. Visual scores, taproot and adventitious root volumes and foliage weight were recorded. In all experiments significant differences (P < 0.01) in average spring vigor score were found among the five root classes. Correlation coefficients between spring vigor and adventitious root scores were 0.49, 0.65 and 0.58 for exp. 1 (springs of 1988 and 1989) and exp. 2, respectively. Adventitious root volume made up 86% of total root volume in exp. 2. Significant positive linear relationships were found between foliage weight and adventitious root and taproot volumes. It was concluded that profuse production of adventitious roots imparts better spring vigor to red clover. Key words: Taproot, adventitious root, red clover

Lateral meristems and stem thickening growth in monocotyledons

Although monocotyledons lack a vascular cambium of the type found in dicotyledons and conifers, lateral meristems still play an important role in the establishment of their growth habits. The presence near the shoot apex of a primary thickening meristem (PTM), which is probably plesiomorphic in monocotyledons, predisposes evolution into the many pachycaul forms. A PTM occurs in virtually all monocotyledons, whereas the secondary thickening meristem (STM), which is morphologically similar, is limited to a few genera of Liliiflorae. these records are reviewed in a systematic context. To a greater or lesser extent in different taxa, the PTM is responsible for primary stem thickening, adventitious root production, and formation of linkages between stem, root and leaf vasculature. The STM largely contributes to the body of the stem. The sometimes obscure distinction between the two meristems, and their relationship with other stem meristems are discussed. For systematic purposes stem thickening in monocotyledons is separated into two characters: diffuse growth (as in palms), and growth by means of lateral meristems. The three states of the second character are represented by the first three of Mangin’s (1882) four categories (two herbaceous, the third arborescent): (1) The lateral meristem is limited in extent, and ceases activity after root formation. (2) It remains active for a limited period after cessation of root formation, contributing to the plant body. (3) It remains active throughout the life of the plant, contributing the bulk of the plant body.

The effect of photoperiod and temperature on growth and frost resistance of winter rye root systems

Root growth, development and frost resistance were examined in winter rye (Secale cereale L. cv. Puma) plants grown under 6 combinations of temperature and photoperiod (20/16°C or 5/3°C, day/night; 8, 16‐ or 24‐h days). Overall root system growth is influenced by the interaction of temperature and photoperiod. Maximum shoot growth occurs at a 24‐h photoperiod in 20°C plants and at a 16‐h photoperiod in 5°C plants, and is correlated in both treatments with a high root:shoot ratio. Frost resistance of rye roots is affected by short photoperiods in 2 ways. First, short photoperiod and low temperature delay production of new adventitious roots so that newly developing roots are not exposed to freezing temperatures. Second, short photoperiod alone can induce several degrees of frost tolerance in existing roots during the lag phase of growth. Low temperature alone does not decrease the rate of dry weight accumulation in rye root systems, but cold temperature does retard developmental processes within the roots. Rye roots grown at 5°C develop first order lateral roots, differentiate metaxylem vessels and suberize endodermal cell walls more slowly than roots grown at 20°C.

In vitro propagation of mulberry ( Morus alba L.) through nodal segments

Nodal explants of mulberry ( Morus alba L.), bearing an axillary bud, and obtained from in vitro raised seedlings were used to initiate shoot cultures. Murashige and Skoog medium supplemented with 3% sucrose and 2.5 μM N 6-benzyl adenine resulted in a maximum rate of shoot multiplication (up to 13-fold) as expressed in terms of the number of nodes (propagules) formed per shoot. Nodal segments from 3–4-year-old greenhouse-grown plants behaved similarly. Nodal explants from different seedlings exhibited highly significant differences in the rate of shoot multiplication. In addition, the position of the nodal segment on the parent shoot determined the rate of shoot multiplication, with a basipetally increasing gradient in the growth response of the segments being observed. The cultured nodal segments could be cold stored at 4°C for at least 6 months without any loss of multiplication rate on subsequent culture at 25°C. The in vitro formed shoots underwent spontaneous rooting, after being on shoot proliferation medium for more than 4 weeks. Addition of activated charcoal (0.05 or 0.1%) to the shoot proliferation medium speeded up the production of adventitious roots by at least 2 weeks and inhibited the formation of callus at the basal end of the shoots. The rooted shoots could be transplanted to sand-vermiculite (1:1) mixture in the greenhouse with 100% transplantation success.

Effects of waterlogging on the growth and water relations of three Pinus taxa

The response of Caribbean pine ( Pinus caribaea Morelet. var. hondurensis Barr. and Golf.), slash pine ( Pinus elliottii Englem. var. elliottii) and their F 1 hybrid to soil waterlogging was studied under glasshouse conditions. Plants were grown in either a lateritic or gleyed podzolic soil and pots were flooded in both autumn and summer treatments. Plant responses were influenced by both season and duration of flooding, and by soil type. All the Caribbean pine seedlings survived the autumn flooding, but showed very slow growth and had very low needle conductances. Summer-flooded plants exhibited rapid stomatal closure and low needle water-potentials accompanied by needle dehydration. All of the summer-flooded Caribbean pine seedlings died. Slash pine was much more flood-tolerant than was Caribbean pine, whilst the F 1 hybrid was intermediate between the two parents. All slash pine and F 1 hybrid seedlings survived autumn flooding and continued to grow, but survival was reduced with summer flooding, particularly in the short-term flooding treatment. Slash pine and F 1 hybrid seedlings showed morphological features of flood tolerance with production of adventitious roots and formation of lenticels in association with stem hypertrophy. Although stomatal opening was evident during autumn flooding, needle conductance was very much reduced in summer-flooded plants of these two taxa. Needle water-potential and relative water content were maintained near the control value in flooded slash pine grown in both soil types, but only for the F 1 hybrid in the flooded lateritic podzolic soil.

Metabolism and distribution of grasses in tropical flooded savannas in Venezuela

ABSTRACTFlooded savannas in south-west Venezuela consist of seasonal, marshy and flooded grassland communities, the distribution of which depends on soil level. Seasonal grasslands are dominated by tuft-forming, rhizomatous C4-grasses (exemplified byPaspalum chaffanjoniiin this study), while flooded grasslands are dominated by stoloniferous grasses which develop rooted, floating culms during the rainy season(Leersia hexandraandHymenachne amplexi-caulis).The interface between these two communities is a marshy grassland dominated by stoloniferous grass species which tolerate flooding to a depth of 10 to 25 cm(Panicum laxumandLeersia hexandra).All perennial grass species in flooded grasslands behave as typical C3 plants, while marshy grasslands are dominated byPanicum laxum,a species with reduced photo-respiration, low RuBP/PEP-carboxylase ratios, and low absolute RuBP-carboxylase activity compared to C3 grasses. It also has lower photosynthetic rates than the other grass species.Hymenachne amplexicaulisappears to be the least drought tolerant from the species selected, in accordance with its distribution in the wettest side of the flooding gradient studied. The other species showed marked reduction in relative water content and pronounced increase in leaf proline content in drought experiments lasting 6 to 30 days. Alcohol dehydrogenase increased markedly in response to anaerobiosis in the root environment in the tuft forming grasses, while the stoloniferous species with ascending culms were least affected by this treatment, probably as a result of better aeration inside the culms and also to the production of adventitious roots in upper nodes. Nitrate reductase activity increased as a result of anaerobiosis in the roots but not in the leaves, of all species exceptLeersia hexandra.No difference among the species was found in malate accumulation, or the activity of malic enzyme.

Effects of Establishment Method on Root Form of Lodgepole Pine and Sitka Spruce and on the Production of Adventitious Roots

Root systems of lodgepole pine and Sitka spruce were measured 15 years after establishment from bare-rooted transplants and direct sowing on a ploughed peat site. On one sample the root systems were divided into eight sectors in plan view for dry weight analysis and measurements were made on branching frequency. On another sample the five largest lateral roots on the Sitka spruce were dissected and sectioned to find whether they originated from the original root system or adventitiously from the stem. Root system form was considerably influenced by the ploughing, with the largest part of the dry weight contained in sectors which included the plough ridge. Although both species were affected to the same degree by the ploughing, statistical analysis showed that the distribution of root weight was more symmetric in the spruce than in the pine. Rooting depth, which was limited by waterlogging, was greater in pine than in spruce, and the development of a taproot from the seedling radical in the direct sown trees did not influence maximum rooting depth. The frequency of major root branches and the incidence of branches arising from injury were similar in all treatments. In the spruce, most of the transplants had major roots of adventitious origin, but adventitious roots were uncommon in the direct sown trees. In the transplants adventitious roots were most frequent (74–84 per cent) in the two largest of the five main roots and least abundant (10 per cent) in the two smallest. The size class distribution of the five main roots was less even in the transplants than in the sown trees, with greater allocation to the largest roots.

Chloramphenicol effects on adventitious root production by radish hypocotyls

Abstract The excision of the root accelerates greatly the formation of adventitious roots in the hypocotyl of etiolated radish seedlings, but if the seedlings develop in CAP 1×10−4M, no adventitious root are induced after cutting. IAA either alone or associated with CAP, significantly increases the number of primordia in normal hypocotyls if given at the moment of cutting, while it has not stimulatory effect on the hypocotyls of seedlings grown in CAP. IAA has significant effect on both elongation and tickening of hypocotyl segments prepared from seedlings grown in CAP, and this could indicate a specific action of the inhibitor either on a particular process or on particular cells. The endodermis and the pericycle, which are the two cell layers implicated in the formation of the adventitious roots, could be the mediators of this particular effect of CAP in rooting.

The control of adventitious root production in tissue-cultured Douglas-fir

Rooting percentage and root number in tissue-cultured Douglas-fir (Pseudotsugamenziesii (Mirb.) Franco) were influenced by the rooting substrate, the concentration of sucrose and boron in the rooting medium, shoot height, and shoot generation. Peat–perlite was a better substrate than agar, producing 70% compared with 0% rooted shoots, respectively. On peat–perlite, cell divisions were organized and were associated with tracheid nests, whereas on agar proliferation was unorganized and not restricted to the nests. A sucrose concentration of 4% was optimal for the production of nodular or rooted shoots. At 4% sucrose and 3 mg •L−1 boric acid, 100% of the shoots rooted, and the mean root number was 11. Rooting percentage and root number were significantly higher with shoots that were 3 cm tall than 2 or 1 cm tall shoots. Finally, it was found that shoot responses were more rapid in third and fourth generation shoots than in second generation shoots. At least 80% were rooted or nodular after 4 weeks, compared with only 36% from the second generation.

Vegetative regeneration by layering inCalluna Vulgaris(L.) Hull

Summary The influence of various media on the production of adventitious roots in the stems of degenerate Calluna vulgaris was investigated. An experimental study in a wet heathland, and a survey of layering occurrence in a dry heathland, were carried out in North East Scotland. In the wet heath, adventitious root production was more prof use in peat and soil, and less so in Hypnum jutlandicum and sterile soil. In the dry heath, layering was observed more commonly in moss communities containing Hylocomium splendens and in bare soil, than would be expected if there were no preference. It is suggested that the presence of micro-organisms in the soil stimulates root extension once roots occur. The greater occurrence of layering in Hylocomium communities may be a result of the fast upward growth of this moss covering the lower parts of ramets and causing separation of branches. Scarification of the bark appears to stimulate root initiation. Root production varies between individual plants however, for reasons...

Adaptations to intermittent drying in germinating Eucalyptus sieberi L. Johnson seeds and young seedlings

Before Eucalyptus sieberi L. Johnson seeds germinate, the protein reserves in a small group of cells in the collet are mobilized and the cells swell sufficiently to break the seed coat allowing further water uptake. If the seedling is desiccated at this stage, the embryo remains viable and when the seed is rewetted reserves are mobilized in the cells immediately behind those which expanded initially. Mobilization of reserves and subsequent cell elongation occur sequentially along the hypocotyl after successive dry periods until the reserves are exhausted. Early in the sequence, the distal end of the hypocotyl extends and is positively geotropic, whereas at the end of the sequence the proximal end of the hypocotyl extends and is negatively geotropic, raising the cotyledons rapidly. If the radicle is destroyed or unable to elongate, it is replaced by two adventitious roots, one below the petiole of each cotyledon. Indole acetic acid and sucrose can substitute for the cotyledons in the production of adventitious roots.

Physiological and Growth Responses to Flooding of Seedlings of Hevea brasiliensis

Flooding of soil for 12 wk induced leaf epinasty, reduced chlorophyll content, accelerated ethylene production, inhibited growth, induced decay of roots, and stimulated production of hypertrophied lenticels and adventitious roots on 46-day-old Hevea brasiliensis seedlings. Marked variations were shown among three families of Hevea in response to flooding. The importance of genetic variations in flood tolerance of H. brasiliensis is emphasized. ALTHOUGH RUBBER (Hevea brasiliensis Muell. Arg.) trees are usually grown on deep, well aerated upland soils, they also have been planted on periodically flooded soils (Dijkman 1951, Moraes 1977). However, little quantitative information is available on how poorly aerated soils affect growth of young Hevea trees, or if selection of floodtolerant planting stock is feasible. It is well known that imbalances in physiological responses induced by environmental stresses are good indicators of subsequent growth reduction and injury of trees. For example, changes in water, carbohydrate, and mineral relations induced by flooding lead to leaf abscission, reduction in growth, and mortality of many species of woody plants (Kozlowski 1984a, Kozlowski & Pallardy 1984). With these considerations in mind, experiments were conducted on effects of soil inundation on water relations, growth, and morphology of seedlings of three families of H. brasiliensis.

Effects of Flooding and Nutrient Enrichment on Biomass Allocation in Acer rubrum Seedlings

A greenhouse experiment was conducted on Acer rubrum seedlings to evaluate the effects of flood frequency on production and allocation of biomass and to test the effects of N and P fertilization on production and allocation. Seedlings from the Dismal Swamp were subjected to three flood treatments (no flooding, intermittent flooding, and continuous flooding) and four enrichment treatments (no enrichment, N additions, P additions, and N + P additions). More continuous flooding resulted in less biomass production. Biomass increased during the study in all treatments except for root mass in the continuously flooded treatment. However, production of abundant adventitious roots compensated for the lack of normal root growth. Root/shoot ratios exhibited the greatest decreases in the continuously flooded plants. Plants with N + P added had significantly more leaf, stem, and total mass than the nonenriched plants four months into the study. The N + P additions had apparently compensated for the effects of flood stress in the continuously flooded plants by the end of the study. The fertilized seedlings accumulated higher concentrations of N and P, but their nutrient use efficiency (biomass production per unit nutrient absorbed) was lower than in the nonenriched plants. Acer rubrum seedlings survive flooded conditions through several adaptations; however, theirgrowth is slowed by continuous flooding.

EFFECTS OF FLOODING AND NUTRIENT ENRICHMENT ON BIOMASS ALLOCATION IN ACER RUBRUM SEEDLINGS

A greenhouse experiment was conducted on Acer rubrum seedlings to evaluate the effects of flood frequency on production and allocation of biomass and to test the effects of N and P fertilization on production and allocation. Seedlings from the Dismal Swamp were subjected to three flood treatments (no flooding, intermittent flooding, and continuous flooding) and four enrichment treatments (no enrichment, N additions, P additions, and N + P additions). More continuous flooding resulted in less biomass production. Biomass increased during the study in all treatments except for root mass in the continuously flooded treatment. However, production of abundant adventitious roots compensated for the lack of normal root growth. Root/shoot ratios exhibited the greatest decreases in the continuously flooded plants. Plants with N + P added had significantly more leaf, stem, and total mass than the nonenriched plants four months into the study. The N + P additions had apparently compensated for the effects of flood stress in the continuously flooded plants by the end of the study. The fertilized seedlings accumulated higher concentrations of N and P, but their nutrient use efficiency (biomass production per unit nutrient absorbed) was lower than in the nonenriched plants. Acer rubrum seedlings survive flooded conditions through several adaptations; however, theirgrowth is slowed by continuous flooding.

Regulation by auxin and ethylene of responses of Acer negundo seedlings to flooding of soil

Flooding of soil reduced growth, altered stem anatomy and stimulated ethylene production of Acer negundo L. seedlings. Inhibition of basipetal auxin transport in flooded seedlings by application of NPA (1- N-naphthylphthalamic acid) to stems reduced formation of adventitious roots, width of the xylem increment and the number of vessels in the submerged stem, but had little effect on bark growth. Application of NAA (naphthalene acetic acid) below the height of NPA application restimulated production of adventitious roots and increased vessel numbers, but had little effect on bark thickness or xylem increment. Apically produced auxins appeared to have a predominant role in formation of adventitious roots and vessels, and a lesser role in regulating bark growth and xylem increment. Ethylene appeared to have a major role in regulating leaf epinasty, senescence and abscission as well as production of hypertrophied lenticels and growth of bark tissues.

Sur la variabilité de la capacité rhizogène d'explantats racinaires de Cichorium intybus (var. Witloof) cultivés in vitro : influence de la dimension des explantats initiaux et de la durée de conservation des racines au froid

On Cichorium intybus root explants of different size, it is possible to demonstrate the existence of a relation between the volume/surface ratio and adventitious root formation capacities. With a volume/surface ratio equal to one, the highest number of adventitious roots and percentage of explants able to produce roots have been observed. When this ratio deviates from unity, adventitious root formation declines. Cold storage of chicory roots causes breakdown of fructosans and accumulation of sucrose, glucose, and fructose. At the same time, adventitious root formation on explants cultured in vitro decreases. Inclusion of glucose in culture media increases adventitious root production whatever the duration of chicory root cold storage may have been. Results are discussed and the hypothesis of a regulation of adventitious roots by sucrose and reducing sugars is advanced.