The Influence of NAA, BA and Temperature on Shoot and Root Development from Begonia×cheimantha Petiole Segments Grown in vitro

The effect of exogenously supplied NAA and BA on the shoot and root formation in isolated petiole segments of Begonia×cheimantha was determined in vitro on a modified White medium at a constant temperature of 24°C. The best development of normally appearing plants was obtained on media containing 0.01 mg × 1^?1 of NAA and 0.5 to 1.0 mg × 1^?1 of BA. Lower concentrations of BA yielded no shoots, higher concentrations promoted shoot formation, but the shoots were abnormal with malformed leaves. Lower concentrations of NAA resulted in poorer survival rate and no roots, with higher concentrations of NAA many roots developed, but these were thickened and their longitudinal growth inhibited. Temperature proved to be of utmost importance for the induction of shoot formation. Thus significantly fewer shoots were formed at the higher temperature (25°C) than at lower temperatures (15 to 20°C). Temperature immediately after initial transfer was of greatest importance: 25°C, during the first week followed by low temperature, produced very few shoots.     

Encapsulation, cold storage, and growth of Hibiscus moscheutos nodal segments

Nodal segments of Hibiscus moscheutos (hardy hibiscus) were excised from proliferating axillary shoot cultures and encapsulated in high density sodium alginate hardened by 50 mM CaCl₂. Nodal segments 4 mm long grew as well as and were easier to encapsulate than 8 mm long nodal segments. Although nodal segments grew regardless of the concentration of sodium alginate, 2.75% was determined to produce the highest quality encapsulated nodal segments beads (sufficient alginate coating and ease of use) because of the viscosity produced by the 2.75% sodium alginate solution. When encapsulated segments were stored at 5°C they did not grow in light or darkness. During the first month on fresh proliferation medium under normal incubation conditions following 5°C storage in the dark for up to 24 weeks, root number and root and shoot elongation were inhibited linearly as storage time increased. All encapsulated nodal segments survived 24 weeks of 5°C storage in two separate experiments. In fact, 80% of encapsulated hardy hibiscus nodal segments survived refrigerated storage for 1½ years (78 weeks) and after 3 months on proliferation medium, the nodal segments produced nearly the same length axillary shoots with the same number of axillary nodes per shoot as compared to encapsulated segments either not stored at 5°C or stored for 24 weeks at 5°C. Growth from encapsulated and cold-stored ‘Lord Baltimore’ nodal segments was more vigorous than from ‘Southern Belle’ nodal segments.     

Effects of post-chilling temperature on growth and variegation in Solomon's Seal

Effects of temperature were studied on the current and following season's growth of shoots from chilled rhizomes of Variegated Solomon's Seal. The rate of progress to completed elongation of the aerial shoot in chilled plants increased linearly with increasing temperature up to 28°C (24 h mean). A post‐chilling thermal time of 658 ± 47°Cd (> ‐1.3°C) was required for aerial shoots to become fully extended. Temperatures of 28°C and 33°C accelerated aerial shoot senescence and decreased rhizome and root dry weights, as compared with 18°C and 23°C treatments. Leaf number and variegation were not affected by temperature treatments during current growth season and all plants produced 12–13 leaves with between 7% and 9% leaf area variegated. Leaf variegation, however, was significantly increased in plants that had been grown after chilling at 28°C during the preceding growing season. Proteins of approximately 26, 32 and 62 kDa were present in the green parts of leaves but not in the white parts.     

Mediation of high-temperature injury by roots and shoots during reproductive growth of wheat

Abstract Previous studies suggest that high temperature stress on wheat (Triticum aestivum L.) involves root processes and acceleration of monocarpic senescence. Physiological changes in wheat roots and shoots were investigated to elucidate their relationship to injury from elevated temperatures after anthesis. Plants were grown under uniform conditions until 10 d after anthesis, when shoot/root regimes of 25°C/25°C, 25°C/35°C, 35°C/25°C and 35°C/35°C were imposed. Growth and senescence of shoots and grain were influenced more by root temperatures than by shoot temperatures. High root temperatures increased activities of protease and RNasc enzymes, and loss of chlorophyll, protein and RNA from shoots, whereas low root temperatures had opposite effects. High root temperatures appeared to induce shoot senescence directly. High shoot temperatures probably disrupted root processes, including export of cytokinins, and induced high leaf protease activity, senescence and cessation of grain development. The authors concluded that responses of wheat to high temperatures, whether of roots or shoots, are manifested as acceleration of senescence and may be mediated by roots during grain development.     

Arbuscular mycorrhiza colonization and development at suboptimal root zone temperature

Temperature has a strong influence on the activity of living organisms. This study, involving two indoor experiments, evaluated the effects of root zone temperature (10, 15 and 23°C) on the formation and development of arbuscular mycorrhizae (AM). In the first trial, greenhouse-grown sorghum [Sorghum bicolor (L.) Moench] was either colonized by Glomus intraradices Schenck & Smith or left non-mycorrhizal. Root length, root and shoot weight and root colonization were measured after 5, 10 and 15 weeks of plant growth. Although suboptimal root zone temperatures reduced growth in both mycorrhizal and non-mycorrhizal plants, mycorrhizal plants were larger than non-mycorrhizal plants after 15 weeks at 15 and 23°C. At suboptimal root zone temperatures, mycorrhizal inoculation sometimes slightly reduced root development. AM colonization was more affected than root growth at suboptimal root zone temperatures. Colonization was markedly reduced at 15°C compared with 23°C, and almost completely inhibited at 10°C. The second experiment was conducted in vitro using transformed carrot (Daucus carota L.) roots supporting G. intraradices. Mycelium length and spore number were measured weekly for 15 weeks. Spore metabolic activity (iodonitrotetrazolium reduction), root length and percentage root colonization were measured after 15 weeks. G. intraradices sporulation was reduced at temperatures below 23°C, while spore metabolic activity was significantly reduced only at 10°C. Root length and in particular percentage colonization were decreased at suboptimal temperatures. A negative interaction between AM hyphal growth and root growth resulting in reduced probability of contact at suboptimal root zone temperatures is proposed to explain the greater reduction observed in root colonization than in root and hyphal growth.     

Factors Affecting Flower Abortion and Malformation in Roses

The formation of blind shoots and malformed flowers in rose plants grown under various temperatures and light intensities, and subjected to different cut back procedures has been studied. Low temperature, low light intensity and low cut back promoted blind shoot formation. Hybrid tea cultivars are more sensitive for unfavourable temperature, light and cut back treatments than Floribunda cultivars. The process of floral abortion is initiated during the early stages of shoot growth before the differentiation of floral parts has been completed. Low temperatures (12–15°C) in this critical stage of development strongly promote blind shoot formation, but have no effect when stamen and pistil primordia had been formed in the apical flower bud. The formation of malformed flowers, so-called “bullheads”, which have significantly more petals than normal flowers, is also promoted by low temperature and low cut back. Light intensity seems to have no effect. Shoots subjected to low temperature (12°C) during the early stages of development, before the differentiation of the floral organs are fully completed, produce malformed flowers to a greater extent than shoots subjected to high temperature (18–24°C) during this period. It is suggested that blind shoot formation in roses is subject to hormonal control.     

Low-temperature pretreatment of the root system of Brassica rapa L. plants: effects on the xylem sap exudation and on the nitrate absorption rate

Brassica rapa plants were exposed for a 52 h period (as pretreatment) to a differential temperature (DT) between roots (5°C) and shoots (20°C), while control plants were maintained with both shoot and roots at 20°C (warm grown = WG). Measured at 20°C, volume flow of xylem exudate from roots of DT plants was enhanced compared with that from WG plants, while transpiration flows were similar in pretreated and control plants. Both transpiration and exudation flows were dependent upon shoot/root ratio. Differences in the volume flow of exudate were principally related to increases in root hydraulic conductance. Anion fluxes (notably nitrate) into xylem exudate of DT plants were significantly greater than those into exudate of WG plants. This enhancement of nitrate flow from the pretreated roots was associated with a two-fold increase in nitrate uptake rate. The relationship of the cold-induced change in nitrate uptake capacity with shoot/root ratio is discussed in terms of control of nitrate absorption by shoot sink strength.     

In vitro Organogenesis in Explants from Different Cultivars of Begonia X hiemalis

Petiole explants from 17 cultivars of Begonia X hiemalis were grown on a basal agar medium with different combinations of NAA and BA as well as on media lacking microelements or vitamins. The stock plants were kept either under short days (7–8 h of light perday) at 15°C or under long days (15–16 h of light) at 18–21°C. The day length during the in vitro culture was 20 h of light and the temperature 21°C. Explants from short-day treated stock plants did not show any differentiation. In explants from long-day treated stock plants, the percentage of explants with shoot, root and with both shoot and root initiation were recorded after 55 days. Explants forming both shoots and roots were transferred to soil, and plantlet formation was observed after another 55 days. The percentage of explants with organ and plantlet formation differed between cultivars. With increasing NAA and decreasing BA concentrations, the percentage of explants forming only roots increased, whereas the percentage of explants with only shoots decreased. Plantlet formation was most frequent in explants from NAA: BA ratios of 2: 1 and 10: 1, and a variation was found between different cultivars. When the vitamin fraction was not added to the medium, this did not influence formation of shoots, roots and plantlets. When the microelements were omitted. shoots, roots and callus were formed, but no plantlets.     

In vitro conservation of chestnut (Castanea sativa) by slow growth

Slow growth storage has been achieved for Castanea sativa (cv. ‘Montemarano’) shoot cultures over a duration of 48 mo at a temperature of 8°C, where 82% of explants survived and were able to resume normal growth after transfer to standard culture conditions at 23°C. The evaluation of the chlorophyll content of leaves also showed no differences between material stored for 48 mo and control material subcultured at 23°C. With a storage temperature of 4°C, the survival of shoots was significantly lower at approximately 56% after 12 mo, and no plants recovered after 24-mo storage. The presence of 6-benzyladenine 0.44 μM in the culture medium proved to be necessary for the recovery of healthy shoots, while pre-treatments with different concentrations of abscisic acid did not significantly influence the survival of shoots following storage conditions. A low level of light during slow growth storage resulted in positive effects on the rate of shoot survival over the longest preservation periods.     

Micropropagation of Ajuga bracteosa, a medicinal herb

For conservation and genetic transformation, a successful in vitro micropropagation protocol for Ajuga bracteosa, a medicinal herb has been established for the first time. MS medium supplemented with IAA (2 mg/L) and BA (5 mg/L) induced 100 % shoot regeneration with an average of 41.4 shoots of 8.4 cm per culture. Excised in vitro shoots when transferred to MS + IBA (0.5 mg/L) produced 20 roots/shoot of 20.2 cm average length in 100 % cultures. Of the three explants, leaf, petiole and root, leaf displayed quickest response followed by petiole while root was the slowest. Hardening of plantlets was achieved with 82 % survival. The hardened plants were maintained in pots with garden soil under controlled (Temp. 25?±?2 °C) conditions. RAPD exhibited genetic fidelity with 100 % monomorphism in regenerants.     

Development of Asparagus plumosus Shoot Tips Grown in vitro

Lateral shoot tips from young Asparagus setaceus (Kunth) Jessop (syn. A. plumosus Baker) shoots were grown on a modified Murashige and Skoog medium. Tips from 5 to 20 mm lateral shoots had significantly better growth and development than tips from lateral shoots (2 mm) still covered by leaf-scale. The optimum temperature for growth and development of the explants was 17 to 24°C. The initial growth was fast at 24°C but stopped after about 4 weeks. At 17°C the growth was slow but in return the cultures continued to grow. Kinetin was necessary for growth. Without any kinetin all cultures died. Optimum growth was found with 2 mg/l kinetin. There was no growth at all with IAA alone. A low IAA concentration had no effect, but at high concentrations IAA inhibited the kinetin induced growth.     

Photoperiod and Temperature Interactions in Growth and Flowering of Strawberry

Growth and flowering of strawberry cultivars were studied in controlled environments. Early cultivars adapted to marginal growing areas in Scandinavia initiated flower buds in all photoperiods including continuous light at temperatures of 12 and 18°C. At 24°C they remained vegetative in photoperiods above 14 or 16 h. The later cultivars ‘Senga Sengana’ and ‘Abundance’ did not initiate flower buds in 24-h photoperiods at any of these temperatures. Their critical photoperiod changed from above 16 h at 12°C to about 14 and 13 h at 18 and 24°C, respectively. It is concluded that at high latitudes temperature is as important as photoperiod in controlling flowering in the strawberry. Stolon formation, petiole elongation, and leaf area growth were stimulated by high temperature and long days, usually with optima at 16 h and 18°C for petiole elongation and 16 h and 24°C for stolon formation. Although growth and flowering responses in general were opposite, the results indicate that they are to some extent independent. The photoperiodic growth responses were mainly of morphogenetic nature. Dry weight of stem and leaves was little influenced by photoperiod when the irradiance was kept constant.     

Water relations under root chilling in a sensitive and tolerant tomato species

The shoots of cultivated tomato (Lycopersicon esculentum cv. T5) wilt if their roots are exposed to chilling temperatures of around 5 °C. Under the same treatment, a chilling‐tolerant congener (Lycopersicon hirsutum LA 1778) maintains shoot turgor. To determine the physiological basis of this differential response, the effect of chilling on both excised roots and roots of intact plants in pressure chambers were investigated. In excised roots and intact plants, root hydraulic conductance declined with temperature to nearly twice the extent expected from the temperature dependence of the viscosity of water, but the response was similar in both species. The species differed markedly, however, in stomatal behaviour: in L. hirsutum, stomatal conductance declined as root temperatures were lowered, whereas the stomata of L. esculentum remained open until the roots reached 5 °C, and the plants became flaccid and suffered damage. Grafted plants with the shoots of one genotype and roots of another indicated that the differential stomatal behaviour during root chilling has distinct shoot and root components.     

Effects of temperature,photoperiod and culture vessel size on adventitious shoot production of in vitro propagated <Emphasis Type="Italic">Huernia hystrix</Emphasis>

High production costs due to low growth rate in vitro and high labour costs are among factors limiting commercial application of micropropagation techniques. The low growth rate could be due to unfavourable or sub-optimal environmental and chemical conditions of the cultures. The effects of temperature, photoperiod and culture vessel size were investigated on adventitious shoot production of Huernia hystrix. There were significant increases in shoot proliferation with increased temperature in cultures maintained under a 16 h photoperiod. Slow growth observed at low temperatures (15 and 20°C) offers a potential strategy for cost-effective in vitro storage of H. hystrix germplasm. The maximum adventitious shoots produced per explant and percentage of explants producing shoots (4.2 ± 0.74 and 94% respectively) were observed in cultures maintained at 35°C, the optimum temperature for photosynthesis in plants possessing crassulacean acid metabolism (CAM). The nocturnal accumulation of organic acids in cultures incubated under a 16 h photoperiod further suggest the presence of CAM in this species. On the other hand, cultures kept under continuous light appear to shift to a C-3 photosynthetic pathway. There was a significant decrease in fresh weight of adventitious shoots regenerated per explant as temperature increased. The use of larger culture vessels further increased the shoot proliferation to 5.6 shoots per explant with a potential production of 3,429 shoots per m² in the growth room compared to 2,750 shoots per m² using culture tubes.     

The influence of waterlogging at different temperatures on penetration depth and porosity of roots and on stomatal diffusive resistance of pea and maize seedlings

The 8 days old seedlings of pea (cv. Ilowiecki) and maize (cv. Alma F1) were subjected to differentiated aeration conditions (control — with pore water tension about 15 kPa and flooded treatment) for 12 days at three soil temperatures (7, 15 and 25 °C). The shoots were grown at 25 °C while the soil temperature was differentiated by keeping the cylinders with the soil in thermostated water bath of the appropriate temperature. Lowering the root temperature with respect to the shoot temperature caused under control (oxic) conditions a decrease of the root penetration depth, their mass and porosity as well as a decrease of shoot height, their mass and chlorophyll content; the changes being more pronounced in maize as compared to the pea plants. Flooding the soil diminished the effect of temperature on the investigated parameters; the temperature effect remaining significant only in the case of shoot biomass and root porosity of pea plants. Root porosity of pea plants ranged from 2 to 4 % and that of maize plants — from 4 to 6 % of the root volume. Flooding the soil caused an increase in the root porosity of the pea plants in the entire temperature range and in maize roots at lower temperatures by about 1 % of the root volume. Flooding the soil caused a decrease of root mass and penetration depth as well as a decrease of plant height, biomass and leaf chlorophyll content.     

Partition of photosynthates between shoot and root in spring wheat (Triticum aestivum L.) as a function of soil water potential and root temperature

Low soil water potential and low or high root temperatures are important stresses affecting carbon allocation in plants. This study examines the effects of these stresses on carbon allocation from the perspective of whole plant mass balance. Sixteen-day old spring wheat seedlings were placed in a growth room under precisely controlled root temperatures and soil water potentials. Five soil water potential treatments, from −0.03 MPa to −0.25 MPa, and six root temperature treatments, from 12 to 32°C were used. A mathematical model based on mass balance considerations was used, in combination with experimental measurements of rate of net photosynthesis, leaf area, and shoot/root dry masses to determine photosynthate allocation between shoot and root. Partitioning of photosynthates to roots was the lowest at 22–27°C root temperature regardless soil water potential, and increased at both lower and higher root temperatures. Partitioning of photosynthates to the roots increased with decreasing soil water potential. Under the most favourable conditions, i.e. at −0.03 MPa soil water potential and 27°C root temperature, the largest fraction, 57%, of photosynthates was allocated to the shoots. Under the most stressed conditions, i.e. at −0.25 MPa soil water potential and 32°C root temperature, the largest fraction, more than 80%, of photosynthates was allocated to roots.     

Effects of temperature on parameters of root growth relevant to nutrient uptake: Measurements on oilseed rape and barley grown in flowing nutrient solution

Summary Effects of root temperature on the growth and morphology of roots were measured in oilseed rape (Brassica napus L.) and barley (Hordeum vulgare L.). Plants were grown in flowing solution culture and acclimatized over several weeks to a root temperature of 5°C prior to treatment at a range of root temperatures between 3 and 25°C, with common shoot temperature. Root temperature affected root extension, mean radius, root surface area, numbers and lengths of root hairs. Total root length of rape plants increased with temperature over the range 3–9°C, but was constant at higher temperatures. Root length of barley increased with temperature in the range 3–25°C, by a factor of 27 after 20 days. Root radii had a lognormal distribution and their means decreased with increasing temperature from 0.14 mm at 3°C to 0.08 mm at 25°C. The density of root hairs on the root surface increased by a factor of 4 in rape between 3 and 25°C, but in barley the highest density was at 9°C. The contribution of root hairs to total root surface area was relatively greater in rape than in barley. The changes in root system morphology may be interpreted as adaptive responses to temperature stress on nutrient uptake, providing greater surface area for absorption per unit root weight or length.     

裂叶悬钩子组织培养研究 Ⅰ.裂叶悬钩子叶外植体培养直接再生不定芽及植物激素对它的影响

本文首次报道裂叶悬钩子(Rubus laciniatus Wild)叶外植体培养在改良的NN~(69)培养基上附加2—4mg/1 6-BA和0.1mg/1 NAA或1—3mg/1 2,4-D和0.1mg/1 NAA,两者都可直接从完整叶片、叶片下切段或叶柄诱导出不定芽。诱导频率达20—48%。而不定芽绝大部分发生在叶轴处或叶柄基部。完整叶片的不定芽诱导率与叶片下切段无差别,但比叶柄基部诱导率要高。6-BA对叶轴处不定芽诱导率比2,4-D的要高。此外,不需继代培养,不定芽数可达10—20个,继代培养一个月左右,每个不定芽能形成丛生芽数可达40一60个。另外,本文还讨论了细胞分化过程中的极性现象。     

Callus and Root Formation in Explants of Beta vulgaris

Callus from hypocotyl and petiole explants and anthers of Beta vulgaris L. was initiated on a defined agar medium containing IAA and kinetin. The cultures were kept in light (18 hours a day) at 27C for 5 weeks. Differences in dry matter production and root initiation were found between hypocotyl and petiole explants. No shoots were formed. Callus formation in anthers was very rare.     

Growth and Dormancy in Norway Spruce Ecotypes (Picea abies) I. Interaction of Photoperiod and Temperature

Growth and dormancy as affected by photoperiod and temperature have been studied in Norway spruce ecotypes of different latitudinal and altitudinal origin. First-year seedlings were used. In all ecotypes apical growth cessation and terminal bud formation occurred within 2 weeks after exposure to SD at temperatures of 18 to 24°C. At lower temperatures or at near-critical photoperiods the response was delayed. The critical photoperiod for apical growth cessation varied from 21 hours in ecotype Steinkjer, Norway (64°N) to about 15 hours in ecotype Lankowitz, Austria (47°04′N). High-elevation ecotypes also had longer critical pholoperiods than low-elevation ecotypes from the same latitude. A detectable growth depression resulted from as little as 1 or 2 SDs of 10 hours, and with 4 or more SDs apical growth cessation took place. In contrast to the situation in the shoot, root growth was not affected by photoperiod. Accordingly, the top:root ratio is drastically affected by photoperiod. The critical photoperiod for cambial growth was shorter than that for apical growth in all ecotypes and cambial growth cessation was delayed for several weeks compared with cessation of apical growth. A transition to formation of late-wood tracheids with thick walls and narrow lumens took place upon exposure to SD. The photoperiodic effects were significantly modified by temperature, but the critical photoperiods were only slightly changed by temperature in the range of 12 to 24°C. However, a 10-hour “night” at 4°C caused growth cessation in continuous light in four ecotypes tested. Temperature optimum for apical growth under non-limiting photoperiods (24 hours) was 21°C in all ecotypes, but with little difference among 18,21 and 24°C. The Q₁₀ for apical growth was 3.5 in the temperature range 12 to 18°C. The growth potential as determined in 24-hour photoperiods was not significantly different among the various ecotypes except for one northern eco-type which was clearly inferior to the others. However, the growth of ecotype Steinkjer (64°N) was greatly suppressed even by the long midsummer days at 59°40′N, thus demonstrating the misleading impression one gets of the growth potential of northern ecotypes when they are moved southwards.