Influence of the Irradiance on Carbohydrate Content and Rooting of Cuttings of Pine Seedlings (Pinus sylvestris L.)

Seedlings of Pinus sylvestris L. were grown for 6 weeks at an irradiance of either 8 or 40 watts per square meter in a controlled environment room. Cuttings from these plants were rooted in tap water for 75 days at either 8 or 40 watts per square meter. The photoperiod was 17 hours.

During the first 30 days of the rooting period quantitative changes in carbohydrates were recorded in cuttings from the different treatments. The carbohydrate contents of the cuttings were mainly regulated by the irradiance during the stock plant stage and generally a higher carbohydrate level was found in cuttings from stock plants grown at 40 watts per square meter.

The irradiance during the rooting period had only minor effects on the time course of root formation, whereas the irradiance during the stock plant stage did influence the subsequent root formation. Cuttings from stock plants grown at 8 watts per square meter rooted faster and with higher frequency than those from stock plants grown at 40 watts per square meter. These results are discussed in relation to the mentioned irradiance effects on carbohydrate content.

     

Effects of auxin and irradiance on the rooting of cuttings of Pinus sylvestris

Abstract Seedlings of Pinus sylvestris L. were grown under controlled conditions (temperature 20°C, photoperiod 17 h) at two irradiances, 8 or 40 W m^-2. Hypocotyl cuttings were excised and rooted at different irradiances in tap water solutions of indolebutyric acid (IBA). The fastest rooting and highest rooting percentage were obtained with cuttings from stock plants grown at 8 W m^-2 and treated with 10^-5M IBA for 21 days. The concentration of 10^-4M IBA inhibited root formation. In comparable treatments rooting was always better in cuttings from stock plants grown at 8 W m^-2 than in cuttings from stock plants grown at 40 W m^-2. The irradiance during the rooting period had only a minor influence on rooting. When cuttings from plants irradiated with 40 W m^-2 were treated with 10^-5M IBA for 21 days the rooting percentage almost reached the same level as in untreated cuttings from stock plants given 8 W m^-2. In cuttings treated with IBA during the whole rooting period, rooting was depressed in comparison to untreated cuttings. Aeration of the 10^-4M IBA solution increased the rooting percentage, but aeration had no effect on untreated cuttings and on cuttings treated with lower IBA concentrations.     

Adventitious Root Formation Induced by Gibberellic Acid and Regulated by the Irradiance to the Stock Plants

Pea plants (Pisum sativum L. cv. Alaska) were grown from seeds for eleven days at different irradiances. Cuttings were then excised and rooted at 16 W × m^?2. Gibberellic acid (GA₃, 10^?11 to 10^?3M) was applied to the cuttings immediately after excision. Cuttings from stock plants grown at the highest level of irradiance (38 W × m^?2) formed the lowest number of roots. An increasing number of roots per cutting was obtained by decreasing the irradiance to the stock plants. In cuttings from stock plants grown at low irradiances, low concentrations of GA₃ (10^?8 and 10^?7M) promoted root formation further. No effect on rooting by these GA₃ concentrations was observed when applied to cuttings originating from stock plants grown at the high irradiances. Root formation in all cuttings was inhibited by GA₃ at concentrations higher than 10^?6M. The degree of inhibition by GA₃ was influenced by the irradiance pretreatment and was increased with an increase in the irradiance during the stock plant growth. Seeds from different years produced cuttings with different response patterns regarding the irradiance and GA₃ effects on rooting.     

Seasonal changes in adventitious root formation in hypocotyl cuttings of Pinus sylvestris: Influence of Photoperiod during stock plant growth and of indolebutyric acid treatment of cuttings

Seedlings of Pinus sylvestris were grown for 6 weeks under natural light conditions in a temperature controlled environment room. Cuttings from these plants were rooted in tap water or in indolebutyric acid (IBA) solutions for 60 days at an irradiance of 16 W m^-2. Experiments were performed at 3-week intervals during two growth seasons. — Seasonal changes in root formation were found in control cuttings as well as in IBA treated cuttings. The number of roots and the percentage of cuttings that rooted were high during early spring and autumn. During the summer period hardly any roots were formed. Stimulation of root formation by IBA occurred manily during spring and autumn when cuttings already possessed the ability to form roots. — The influence of photoperiod during stock plant growth was also investigated. Shorter photoperiod resulted in an increase in the number of roots and rooting percentage. The period during summer where rooting was inhibited under natural light conditions was considerably shortened when stock plants were grown at a photoperiod of only 4 h. The results demonstrate the importance of the growing conditions for stock plants for subsequent root formation. The results are discussed with special reference to the role of irradiance.     

Influence of Cotyledon Excision and Sucrose on Root Formation in Pea Cuttings

Sucrose was supplied to stock plants of Pisum sativum L. cv. Alaska grown at different levels of irradiance. There was no significant effect on the rooting of the cuttings by sucrose supply to intact plants regardless of the irradiance. However, an increase in the number of roots per cutting was obtained at increasing concentrations of sucrose when the stock plants had been grown at 4 W m^?2 and their cotyledons had been removed two days before the cuttings were excised. Cotyledons were removed from stock plants at different times before the excision of cuttings with the intent to regulate the endogenous supply of carbohydrate. The number of roots per cutting was reduced by removal of the cotyledons and this reduction was correlated to the number of days the stock plants had grown without cotyledons as well as to the irradiance pre-treatment. A greater reduction occurred in cuttings from plants grown under 4 W m^?2 than from those grown under 38 W m^?2. The growth of the stock plants and the subsequent stem growth of the cuttings was determined by the irradiance to the stock plants and by the time of removal of the cotyledons. Exogenous supply of sucrose had no effect on the stem growth of the cuttings.     

A Relationship between Length of Basis and Adventitious Root Formation in Pea Cuttings

A positive correlation between the length of the basis and the ability of the cuttings to form adventitious roots was observed in pea cuttings. Plants with a different basis length (the third internode) were obtained in different ways: Regulation by the level of irradiance, dark treatment or gibberellic acid. The length of the basis was also regulated by excision of the cuttings at different places on the stock plants. With increasing basis length an increase was found in the number of roots subsequently formed. The results were similar in cuttings from plants grown at different levels of irradiance or from dark treated plants. Optimal rooting was obtained by cutting the plants just above the second scale leaf. Cuttings from plants treated with 10^?3M GA₃ showed the same correlation between the length of the third internode and root formation as found in the other experiments, but the number of roots were at a lower level.     

A relationship between irradiation, carbohydrates and rooting in cuttings of Pisum sativum

Rooting ability was studied for cuttings derived from pea plants ( Pisum sativum , L. cv. Alaska) grown in controlled environment rooms. When the cuttings were rooted at 70 μmol m⁻² s⁻, ¹ (photosynthetic photon flux density) or more, a stock plant irradiance at 100 μmol m⁻² s⁻¹ decreased rooting ability in cuttings compared to 5 μmol m⁻², s⁻¹, However, cuttings rooted at 160 μmol m⁻² s⁻¹ formed more roots compared to 5 (μmol m⁻² s⁻¹. Although a high irradiance increased the number of roots formed, it could not overcome a decreased potential for root formation in stock plants grown at high irradiance. Light compensation point and dark respiration of cuttings decreased by 70% during the rooting period, and the final levels were strongly influenced by the irradiance to the cuttings. Respiratory O₂ uptake decreased in the apex and the base of the cutting from day 2 onwards, whereas a constant level was found in the leaves. Only the content of extractable fructose, glucose, sucrose and starch varied during the early part of the rooting period. We conclude that the observed changes in the cuttings are initiated by excision of the root system, and are not involved in the initiation of adventitious roots.     

Water stress and root formation in pea cuttings

The stock plants of pea (Pistum sativium L. cv. Alaska) grown for 11 days at 16 W m^?2 38 W m^?2 were subjected to different degrees of moisture stress, simulated with polyethyleneglycol (PEG, 6000) for different periods. The cuttings were made at the end of stress treatments, planted in perlite and allowed to root in a mist propagation chamber. The number of adventitious roots formed on the cuttings from non-stressed plants was significantly higher under low (16 W m^?2) than under high (38 W ^m?2) irradiance. However, under the influence of short duration stress the number of roots increased significantly under high but not under low irradiance. There was significantly poor rooting after prolonged stress under both irradiances. The leaf osmotic potential ψ_π showed a greater reduction with increasing degree and duration of stress at 38 W m^?2 than at 16 W m^?2. The differential rooting behaviour as a result of stress levels and irradiances is discussed in the light of available literature on adventitious root formation.     

Adventitious root formation in relation to irradiance and auxin supply

High irradiance during treatment of mung bean cuttings favours root formation in response to supplied auxin, whether the latter is IAA or IBA. On the other hand it is inhibitory towards root formation in the absence of supplied auxin. Light promotes the uptake of¹⁴C-IAA into cuttings and its upward movement into the leaves. When¹⁴C-IAA is applied to leaves of cuttings high irradiance favours movement of radioactivity into the epicotyl and hypocotyl. This movement is also enhanced by concomitant supply of IBA to the base of the cuttings. The irradiance under which stock plants are raised also affects the extent of root formation on cuttings. When cuttings are held in darkness without a supply of exogenous auxin they root best if prepared from seedlings raised under high irradiance. However, transport of¹⁴C-IAA out of leaves of cuttings is favoured when cuttings are prepared from seedlings grown under low irradiance. These observations are discussed in relation to auxin transport, photodestruction and, possibly, metabolism.     

Morphactin and Adventitious Root Formation in Pea Cuttings

Stock plants of pea (Pisum sativum L. cv. Alaska) were grown at different controlled levels of irradiance (4, 16 or 38 W m^?2) for 11 days from sowing. Morphactin (CFM, methyl-2-chloro-9-hydroxy-fluorene-9-carboxylate) was applied to the apex of the stock plants 3 days before cuttings were excised. The cuttings were rooted at 16 W m^?2. High levels of morphactin (>5 × 10^?3 mg l^?1) inhibited root formation in the cuttings. Low concentrations of CFM (5 × 10^?5 mg l^?1) promoted the formation of adventitious roots in cuttings from plants grown at all three levels of irradiance, with the most pronounced effect in cuttings from 4 W m^?2. Measurements of ethylene evolution by CFM-treated plants 3 days after application, revealed a stimulatory effect on ethylene production by high CFM concentrations.     

Propagation of Hedera helix: Influence of irradiance to stock plants, length of internode and topophysis of cutting

Abstract Stock plants of Hedera helix cv. Pittsburgh were grown in controlled environment rooms at four different irradiances (light intensities) 10, 22, 37 or 46 W m^-2 PAR (photosynthetically active radiation). The root formation on single internode cuttings from these stock plants was observed in relation to length of the internodes and the position on the vine (topophysis). The analysis indicated that the root number was primarily dependent on internode length which in turn was dependent on irradiance to stock plants and topophysis. The irradiance of 37 W m^-2 PAR was optimal for internode length and root number and the basal internode was the one which produced the greatest number of roots.     

Dynamics of extractable carbohydrates in Pisum sativum. II. Carbohydrate content and photosynthesis of pea cuttings in relation to irradiance and stock plant temperature and genotype

Rooting ability was studied for cuttings derived from stock plants of wild type pea seedlings and seedings of two mutants deficient in photosystem II activity and chlorophyll. Stock plants were grown at 15, 20, 25 or 30°C at 38 W m^-2. Cuttings were rooted at 20°C and at an irradiance of 16 or 38 W m^-2. The rooting ability seemed to be correlated with the initial carbohydrate content only at 38 W m^-2. Based on the findings of the present study it may be concluded that for pea seedlings the growth temperature is more important than photosynthesis as regards accumulation of extractable carbohydrates. During the rooting period carbohydrates are necessary for root formation, but the effect of the iradiance on the number of roots formed is not mediated by the carbohydrate content. Under specific rooting conditions it is possible to correlate the initial carbohydrate content with the rooting capacity of the cuttings within a phenotype, but not always when different phenotypes are considered. The results indicate a connection between the metabolic activity of the cuttings and their ability to form adventitious roots.     

Effects of Nutrients and Light on Growth and Root Formation in Pisum sativum Cuttings

Cuttings obtained from seedlings of Pisum sativum L. were rooted in water solution. Shoot growth continued after excision and shoot length increased considerably before roots emerged. Increase in dry weight was strongly dependent on light supply. Continued growth was dependent on supply of mineral nutrients to the rooting solution. Mineral nutrients had no or slight influence on the number of roots formed on cuttings from stock plants grown in fertilized soil, but the growth in length of the roots was dependent on the presence of calcium in the solution. Root formation was dependent on photosynthetic products formed after excision. No roots were formed on cuttings kept in the dark. The number of roots increased with increasing irradiance given to the leafy part of the cutting. At a low level of irradiance sucrose supply through the rooting medium increased the number of roots. Light given to the basal part of the cuttings had a strongly inhibitory effect on the number of roots formed. It is concluded that the carbohydrate level easily becomes a limiting factor for root formation in growing pea cuttings. Availability of mineral nutrients influences in the first place the growth of the shoots.     

Influence of the irradiance on phenols content and rooting of Ilex paraguariensis cuttings collected from adult plants

The influence of irradiance on phenolics contents and rooting of Ilex paraguariensis cuttings was studied. Results of the first experiment with stock plants under controlled-irradiance conditions show that when the irradiance level increased from 1.5 to 100 % PPFD, the oxidation of cuttings raised from 19 ± 11 to 88 ± 4 % (r ² = 0.64). At the same time, a strong correlation was observed between total phenolics content and irradiance (r ² = 0.7). In consequence, adventitious rooting diminished from 67 ± 5 to 3 ± 3 % under full radiation (r ² = 0.7). In the second experiment with stock plants subjected to field conditions, the results showed that the rooting process is strongly affected by the genotype (P < 0.0001), while the statistical analysis did not show a correlation between rooting and age of the donor plant. Season had a variable effect and depends on genotype. Although we did not find correlations between the rooting ability and the canopy structure of the stock plants, the position of the branches in the mother plant affected rooting and depended on season in addition to genotype. Concomitantly, the levels of soluble phenolics compounds were higher from leaves subjected to high-irradiance conditions than samples collected from inner canopy; which was coincident with the pattern of cuttings oxidation. In conclusion, our results provide evidences which support the hypothesis that the physiological status of the stock plant at the time that cuttings are excised is of utmost importance for the subsequent rooting of I. paraguariensis cuttings. The influence on soluble phenolics content of different irradiances given to the stock plants negatively affect the rooting process since the product of its oxidation cause the browning and death of the cuttings.     

Reduced irradiance and applied auxin influence carbohydrate relations in Pinus banksiana cuttings during propagation

Untreated and indole-3-butyrie acid-treated (IBA) cuttings from 90-day-old Pinus banksiana Lamb, stock plants were propagated under normal greenhouse irradiance (max. 900 $$mol m^-2 s^-1) and shade (max. 120 $$mol m^-2 s^-1) to determine effects on adventitious rooting and on reducing sugar and starch concentrations in needles and basal stems. In one experiment, cuttings were assessed at days 15 and 25 of propagation for basal 1-cm stem fresh weight, proportion rooted, number of roots and longest root length. In a second experiment with cuttings, basal 1-cm stem fresh weight and concentrations of reducing sugar and starch in needles and basal stems were measured each day for the first 10 days of propagation. Carbohydrate measurements were also made for seedling stock plants as controls for the second experiment. Carbohydrate data for cuttings were primarily evaluated based on net (cutting minus seedling) concentrations, to correct for changes in cuttings not related to adventitious rooting. Increase of basal stem fresh weight and rooting of cuttings, based on all measured variables, occurred in the order: light + IBA > light > shade + IBA > shade. The best rooting required the greater irradiance. Compared to results from cuttings in the light, shading resulted in lesser accumulations of reducing sugars and starch in needles and basal stems. Reducing sugar: starch concentration ratios were significantly greater in shade- vs light-propagated cuttings, IBA treatment did not offset the effects of shade on rooting or on reducing sugar and starch concentrations or ratios. Overall, the results suggested that decreased reducing sugar and starch concentrations and/or their increased ratios are associated with shade-induced poor rooting of P. banksiana cuttings.     

Growth Performance of Cuttings Raised from in vitro and in vivo Propagated Stock Plants of Rosa damascena Mill.

Comparative studies on rooting and growth performance of cuttings raised from in vitro and in vivo grown plants of Rosa damascena are described. Cuttings were treated with different auxins and upon transfer to soil their growth performance was recorded. Overall, the auxin treated cuttings of in vitro raised plants responded better than the cuttings of in vivo raised plants. Optimal response for percentage of rooting, root number, root length and bottom breaks was observed at 100 mg dm^–3 IBA. The cuttings derived from in vitro raised plants showed a significantly better response for percent rooting, root number, root length and bottom buds in control treatments.     

Influence of Nitrogen and Sucrose in the Medium and of Irradiance of the Stock Plants on Root Formation in Pelargonium Petioles Grown in vitro

In vitro root formation was studied in petiole explants from Pelargonium×hortorom Bailey cv. Radio exposed to different irradiance (2.5. 11.6 or 23.0 W/m²). Optimal root formation was found when stock plants were subjected to 2.5 W/m² and explants were grown on a medium with 20 g/I of sucrose and 5.0 mM of nitrogen. The number of roots per explant decreased with increasing nitrogen or sucrose concentrations in the growth medium and with increasing irradiance applied to the stock plants. Variation in temperature (17, 21 or 25°C) did not affect root formation. The number of roots per explant was higher in explants from young petioles than in explants from older petioles. The initial nitrogen content of the explants was highest at the lowest irradiance. The content of reducing sugars and sucrose increased with increasing irradiance. The endogenous levels of lysine, arginine and ornithine were highest at 2.5 W/m² and the levels of proline. alanine, γ-aminobutyric acid, glutamic acid, glutaminc, aspartic acid and asparagine were highest at 23.0 W/m². With rising nitrogen concentration in the medium, the final endogenous content of nitrogen in the explants increased, whereas the content of reducing sugars decreased. When the sucrose concentration in the medium increased, the endogenous content of reducing sugars rose, and the nitrogen level was lowered. Variations in the nitrogen concentration in the growth medium influenced the final level of free amino acids in the explants.     

Quantification of IAA Metabolites in the Early Stages of Adventitious Rooting Might Be Predictive for Subsequent Differences in Rooting Response

Stock mother plants have gained importance in the process of adventitious rooting of woody plants in recent years. The present study reveals the role of the cutting position from a stock mother plant for subsequent rooting. Cuttings of Prunus subhirtella Miq. var. Autumnalis which originated from suckers at the bottom of a tree developed a rooting system of better quality (rooted cutting without callus formation, more main roots) compared to cuttings which originated from shoots at the top of a tree. The latter accumulated significantly more indole-3-acetic acid (IAA) with the highest value of 25.37 μg g^?1 FW on the severance date. These cuttings also contained more indole-3-acetyl-aspartate (IAA-Asp) on the second day after severance with the highest value of 4875.95 μg g^?1 FW compared to cuttings from the bottom-deriving suckers. The latter metabolised IAA primarily via 2-oxindole-3-acetic acid (oxIAA) and indole-3-methanol because the concentrations of these compounds increased at the base of these cuttings. The highest concentration of oxIAA, 8.3 mg ekv. IAA g^?1 FW, was measured 1 h after severance in cuttings from the bottom-derived suckers. With 590.5 ng ekv IAAg^?1 FW, the indole-3-methanol values were also significantly higher in the cuttings from the bottom shoots compared with cuttings from the top of the tree.     

The effect of indole-3-acetylaspartic acid on adventitious root formation on bean cuttings

The influence of indole-3-acetylaspartic acid (IAAsp) on rooting of stem cuttings from bean plants (Phaseolus vulgaris L.) of different ages, cultivated at different temperatures (17°, 21° and 25°C) was studied and compared to that of indole-3-acetic acid (IAA). At a concentration of 10^–4 M, IAAsp only nonsignificantly stimulated adventitious root formation, approximately to the same level as IAA in all treatments. IAAsp at 5×10^–4 M further enhanced rooting, by up 200% of control values, with little influence of temperature conditions and stock plant age. This concentration of IAA usually stimulated rooting more than the conjugate. The largest differences between the effects of IAAsp and IAA occured at the highest cultivation temperature of 25°C where stock plant age also influenced the response. The number of roots produced in comparison with the control, was enhanced from 350% on cuttings from the youngest plants to more than 600% on cuttings from the oldest. In contrast to the conjugate, 5×10^–4 M IAA induced hypocotyl swelling and injury of the epidermis at the base of cuttings, in all treatments.     

Light effects on root formation in aspen and willow cuttings

The effect of light on rooting of leafy cuttings of aspen (Populus tremula × tremuloides) and a willow hybrid (Salix caprea × viminalis) was investigated under controlled conditions in water culture. Two levels of irradiance were used, 40 and 8 W m^?2. The lower level gave the best rooting of aspen cuttings, both when applied to the stock plants before the cuttings were taken and when given to the cuttings during the rooting period. Irradiation of the cutting base during the rooting period inhibited rooting almost completely in aspen and decreased the number of roots formed in the Salix hybrid. Net photosynthesis in the cuttings of Salix decreased considerably after excision and increased again after formation of roots. Indirect evidence indicated that photosynthesis was even more affected in aspen cuttings. The possible roles of carbohydrates and inhibitors in the light effects are discussed.