Differences In Callus Formation Research Articles

“Comparing Locking Compression Plate with Limited Contact Dynamic Compression Plate for the Treatment of Adult Diaphyseal both Bone Forearm Fractures”

Introduction: The human forearm serves an important role in upper extremity function, facilitating placement of the hand in space, thus helping to provide the upper extremity with its unique mobility Fractures involving the bones of forearm present unique problem not encountered with fractures of other long bones. Objective: To evaluate and compare the outcomes of locking compression plate (LCP) with limited contact dynamic compression plate (LC-DCP) for the treatment of adult diaphyseal both bone forearm fractures. Material and Methods: This study conducted in the Department of orthopedics, Mymensingh Medical College Hospital, Mymensingh, Bangladesh from January 2018 to December 2020 included 20 patients with 40 fractures in each group. Patients were selected randomly to receive either LCP (20 patients, 40 fractures) or LC-DCP (20 patients, 40 fractures). Operative time, callus formation, functional outcome and complications were recorded. Results: Mean operative time did not differ significantly in the LCP and LC-DCP group (71.25 and 75.70 minutes respectively) .There was some difference in callus formation and mean time to bone union between the two groups which was significant. However, overall functional outcome did not differ significantly between both the groups. One case had delayed union in the (LC-DCP) group while one patient in each group developed superficial infection. Conclusion: In this prospective study comparing LCP with LC-DCP, the outcomes were equal in terms of final functional outcomes and mean operating time but LCP showed slight advantage in terms of callus formation and mean time to bone union.

“Comparing Locking Compression Plate with Limited Contact Dynamic Compression Plate For the Treatment of Adult Diaphyseal Both Bone Forearm Fractures”

Introduction: The human forearm serves an important role in upper extremity function, facilitating placement of the hand in space, thus helping to provide the upper extremity with its unique mobility Fractures involving the bones of forearm present unique problem not encountered with fractures of other long bones.
 Objective: To evaluate and compare the outcomes of locking compression plate (LCP) with limited contact dynamic compression plate (LC-DCP) for the treatment of adult diaphyseal both bone forearm fractures.
 Material and Methods: This study conducted in the Department of orthopedics, Mymensingh Medical College Hospital, Mymensingh, Bangladesh from January 2018 to December 2020 included 20 patients with 40 fractures in each group. Patients were selected randomly to receive either LCP (20 patients, 40 fractures) or LC-DCP (20 patients, 40 fractures). Operative time, callus formation, functional outcome and complications were recorded.
 Results: Mean operative time did not differ significantly in the LCP and LC-DCP group (71.25 and 75.70 minutes respectively) .There was some difference in callus formation and mean time to bone union between the two groups which was significant. However, overall functional outcome did not differ significantly between both the groups. One case had delayed union in the (LC-DCP) group while one patient in each group developed superficial infection.
 Conclusion: In this prospective study comparing LCP with LC-DCP, the outcomes were equal in terms of final functional outcomes and mean operating time but LCP showed slight advantage in terms of callus formation and mean time to bone union.

Effect of medium composition, genotype and age of explant on the regeneration of hexaploid plants from endosperm culture of tetraploid kiwiberry (Actinidia arguta)

Endosperm, an ephemeral and storage tissue, serves as a source of nutrition and protection during embryo development and germination. It can be used for the cultivation of polyploid plants in vitro. Here, results of plant regeneration and acclimatization from the endosperm-derived calli of four cultivars of Actinidia arguta has been presented. Seeds excised from fresh fruit and dry seeds stored for one year served as the sources of endosperm explants of selected tetraploid cultivars of A. arguta. Callus Induction Medium (CIM; containing 0.25, 0.5, or 1 mg/l of TDZ) and Actinidia Endosperm Medium (AEM; containing 2 mg/l of 2,4-D and 5 mg/l of kinetin) were used to study the organogenic responses of the calli. On AEM, the source of explant did not significantly affect the rate of callus induction for any of the tested cultivars; no organogenic events were observed. In contrast, on CIM both the source of explants and the cultivar origin caused significant differences in callus formation and subsequent organogenic events. Histological and ultrastructural analyses revealed the adventitious nature of shoot bud formation on these media. The most efficient elongation of shoot buds was achieved after transferring organogenic calli with adventitious shoot buds to a medium supplemented with zeatin or meta-topolin. Robust root induction with minimal basal callus formation occurred on the medium with indole-3-acetic acid. Flow cytometric analysis revealed that the nuclear DNA content in the leaves of some regenerants was approximately 50 % higher (4.5 pg/2C) than that in leaves from the tetraploid seedlings (3.1 pg/2C),which confirmed that those regenerants originated from the endosperm. The regeneration of such hexaploid plants was more efficient when endosperm from fresh seeds served as an explant; therefore, fresh rather than dry seeds are recommended for endosperm-derived plant production. The hexaploid plants of A. arguta can serve as an important source of breeding material.

Evaluation of callus formation in distal femur fractures after carbon fiber composite versus stainless steel plate fixation.

Carbon-fiber-reinforced polyetheretherketone (CFR) composite plates have a more favorable stress modulus than stainless steel (SS) plates that may confer an advantage to bridge plating. The purpose of this study was to compare callus formation after CFR and SS plating of distal femur fractures. A retrospective review identified distal femoral fractures treated with CFR (n = 10) and SS (n = 21) plate fixation. Callus formation was measured using the modified Radiographic Union Score for Tibia (mRUST) at 3- and 6-month follow-up by three orthopedic trauma surgeons. Loss of alignment, implant failure, and revision surgeries were reviewed. At 3months, the mRUST in the CFR and SS groups was 9.0 (range, 6.3-12.3) and 6.9 (range, 4.3-11.7), respectively (p = 0.01). At 6months, the mRUST in the CFR and SS groups was 11.4 (range, 7.7-16.0) and 10.5 (range, 6.0-15.7), respectively (p = 0.3). CFR and SS groups had a loss of fracture alignment in 1 (10%) and 1 (5%) patient, respectively (p = 0.5), and an unplanned revision surgery in 0 (0%) and 3 (15%) patients, respectively (p = 0.2). All three revisions surgeries in the SS group were for nonunion repair. Treatment of distal femur fractures with CFR versus SS plating resulted in greater callus formation at 3months. At 6months, there was no difference in callus formation between groups. A larger series of patients is necessary to determine if the observed early increased callus formation confers a benefit to clinical outcomes. Therapeutic level III.

Effects of genotypes and explants on garlic callus production and endogenous hormones

High callus production is a feasible way to improve the propagation coefficient of garlic. It remains unknown how genotypes and explants affect garlic callus formation. In the present investigation, we found that there were significant differences in callus formation among garlic varieties. Tip explants were the best calli-producing source, and 91.05% of the explants from four varieties, on average, formed calli after 45 d of primary culturing. Upper leaf parts explants produced lower values. Among the different varieties and explant types, tip explants of variety T141 induced calli in the shortest time and had the greatest callus fresh weight at 45 d. An endogenous hormone contents analysis showed that auxins (indole-3-acetic acid and methyl indole-3-acetic acetate), cytokinins (trans-zeatin and dihydrozeatin), gibberellins4, 9,15,19,24 and 53, abscisic acid, jasmonic acid, jasmonoyl-L-isoleucine, and dihydrojasmonic acid were significantly greater in the tips than those in the upper leaf parts. High endogenous jasmonic acid content might play important roles in callus formation. These results will help us not only establish an efficient garlic callus induction protocol that can be applied to large-scale callus multiplication and regeneration, and to genetically improvement of garlic production, but also understand endogenous hormone roles in tissue/organ differentiation and dedifferentiation.

Prevention of bone infection after open fracture using a chitosan with ciprofloxacin implant in animal model.

Purpose To evaluate different concentrations of ciprofloxacin to prevent infection after open fracture contaminated with S. aureus in rats using absorbable local delivery system.Methods Fifty-two Wistar rats were assigned to six groups. After 4 weeks, all animals underwent 99mTc-ceftizoxima scintigraphy evaluation, callus formation measurement and histological analysis. ANOVA, t-Student and Kruskal Wallis were used for quantitative variables statistical analysis, whereas qui square and exact Fisher were used for qualitative variables.Results Treatment using 25% and 50% of ciprofloxacin incorporated at the fracture fixation device were effective in preventing bone infection compared to control group (p<0.05). Chitosan were not effective in preventing bone infection when used alone compared to control group (p>0.05). Histological findings demonstrated bone-healing delay with 50% of ciprofloxacin. No difference in callus formation were observed (p>0.05).Conclusion Local delivery treatment for contaminated open fracture using chitosan with ciprofloxacin is effective above 25%.

English

The effect of different concentrations of thidiazuron (TDZ), benzyl amino purine (BAP), kinetin and 2,4-dichlorophenoxy acetic acid (2, 4-D) on callus induction in three elite cassava cultivars (agric-rouge, atinwewe and agblehoundo) was evaluated. Leaf explants harvested from greenhouse-grown cassava were sterilised using different concentrations of commercial bleach commonly called Jik (3.85% NaOCl) at different time intervals. The highest number (94%) of clean explants was obtained when 2% (v/v) Jik was used for 15 min. The explants were cultured in half MS media supplemented with different growth regulators TDZ, BAP, kinetin 2, 4-D, 100 mg/l myo inositol, 2% sucrose and gelled with 0.3% phytagel. Callus formation was observed from the cut edges of the leaves in all cultivars after 10 days in medium supplemented with TDZ, 12 days in BAP medium, and 15 days in kinetin medium. There were significant (p < 0.05) differences in callus formation among all cytokinins types and concentrations. However, there were no significant differences in callus formation in different 2,4-D concentrations. All 2,4-D concentrations produced 100% callus in all the cultivars. However, 2,4-D at 2 µM significantly produced the highest (2.48±0.30) callus weight in cultivar atinwewe. Furthermore, simple sequence repeats (SSR) and sequence-characterized amplified region of the induced calli on TDZ and 2,4-D media indicated the loss of CMD2 gene among induced calli compared to the mother plants. Key words: Cassava, simple sequence repeats (SSR) and sequence-characterized amplified region (SCAR), genetic stability, callus, cytokinins, auxins.

Negative effect of zoledronic acid on tendon-to-bone healing

Background and purpose — Outcome after ligament reconstruction or tendon repair depends on secure tendon-to-bone healing. Increased osteoclastic activity resulting in local bone loss may contribute to delayed healing of the tendon–bone interface. The objective of this study was to evaluate the effect of the bisphosphonate zoledronic acid (ZA) on tendon-to-bone healing.Methods — Wistar rats (n = 92) had their right Achilles tendon cut proximally, pulled through a bone tunnel in the distal tibia and sutured anteriorly. After 1 week animals were randomized to receive a single dose of ZA (0.1 mg/kg IV) or control. Healing was evaluated at 3 and 6 weeks by mechanical testing, dual-energy X-ray absorptiometry and histology including immunohistochemical staining of osteoclasts.Results — ZA treatment resulted in 19% (95% CI 5–33%) lower pullout strength and 43% (95% CI 14–72%) lower stiffness of the tendon–bone interface, compared with control (2-way ANOVA; p = 0.009, p = 0.007). Administration of ZA did not affect bone mineral density (BMD) or bone mineral content (BMC). Histological analyses did not reveal differences in callus formation or osteoclasts between the study groups.Interpretation — ZA reduced pullout strength and stiffness of the tendon–bone interface. The study does not provide support for ZA as adjuvant treatment in tendon-to-bone healing.

Factors influencing grafting success and compatibility of grape rootstocks

The aim of this work was to examine the compatibility of different rootstocks with various wine grape varieties. In the first trial, Vitis vinifera L. cvs. Furmint, Regent, Riesling, Sauvignon Blanc, and Welschriesling were grafted onto Börner, 5BB and SO4 rootstocks. In the second trial Welschriesling was grafted on 12 rootstocks. Their growth during the first year in the vineyard was measured. As an index of compatibility, the percentage of first grade grafted vines as well as dry weight of mature shoots (canes) and roots was determined. After the grafts went through the first phase of healing often called callusing (2–3 weeks of moist warm conditions), the differences in callus formation were greater between years than among rootstocks, which were the most obvious with Furmint as a scion. No good callus formation occurred when cane (rootstock, scion) maturity is not adequate. Such was the case in 2005, there were 24% fewer grafts with fully developed callus than those in 2006. The dry weight of roots was higher on 5BB than on Börner and SO4. Börner rootstock had fewer roots, and the roots were thinner. Welschriesling had good compatibility with all rootstocks (the average grafts success was 67%), but that of 5BB, G251, and G103 (above 80%) was greater than the average. The G103 rootstock had the highest dry weight of roots. Shoot growth in vineyards was above the average with 5BB, SO4, Binova, Börner, and M V rootstocks. All Georgikon rootstocks had a lower cane dry weight per vine than the others.

A prospective study comparing locking compression plate with limited contact dynamic compression plate for the treatment of adult diaphyseal both bone forearm fractures

Introduction: Fractures involving the bones of forearm present unique problem not encountered with fractures of other long bones . The aim of this prospective study was to evaluate and compare the outcomes of locking compression plate (LCP) with limited contact dynamic compression plate(LC-DCP ) for the treatment of adult diaphyseal both bone forearm fractures. Material and methods: This study conducted in the Department of orthopaedics , Regional Institute Of Medical Sciences, Imphal from september 2010 to august 2012 included 20 patients with 40 fractures in each group . Patients were selected randomly to receive either LCP ( 20 patients , 40 fractures ) or LC-DCP( 20 patients , 40 fractures ) . Operative time , callus formation , functional outcome and complications were recorded. Results: Mean operative time did not differ significantly in the LCP and LC-DCP group ( 71.25 and 75.70 minutes respectively ) .There was some difference in callus formation and mean time to bone union between the two groups which was significant . However, overall functional outcome did not differ significantly between both the groups. One case had delayed union in the (LC-DCP) group while one patient in each group developed superficial infection. Conclusion: In this prospective study comparing LCP with LC-DCP , the outcomes were equal in terms of final functional outcomes and mean operating time but LCP showed slight advantage in terms of callus formation and mean time to bone union.

Acceleration of spinal fusion using syngeneic and allogeneic adult adipose derived stem cells in a rat model

Posterolateral spinal fusion is the standard treatment for lumbar compression fractures. Adult adipose tissue-derived stem cells (ASCs) promote osteogenesis in vivo and in vitro. The hypothesis tested in this study was that syngeneic and allogeneic ASCs on a biomaterial scaffold composed of tricalcium phosphate and collagen I will accelerate spinal fusion in a rat model. ASCs from male Fischer or ACI rats were loaded onto scaffolds (53,571 cells/mm(3)) and cultured in stromal media for 48 h. Male Fisher rats were assigned to 4 cohorts (n = 14/cohort) after bilateral decortication of the L4 and L5 transverse processes: (1) No treatment; (2) scaffold only; (3) scaffold + syngeneic ASCs; or (4) scaffold + allogeneic ASCs. Half of each cohort was harvested 4 or 8 weeks after surgery. Spinal fusion was evaluated with radiographs, microcomputed tomography, and light microscopy. Callus did not form in spines without scaffolds. There were no significant differences in callus formation among scaffold cohorts 4 weeks after surgery. Callus formation was more mature in both ASC cohorts versus scaffold alone 8 weeks after surgery based on microstructure as well as radiographic and microcomputed tomographic evidence of active bone formation. Inflammatory cell infiltrate was significantly lower in both ASC cohorts (syngeneic = 18.3 +/- 0.85%; allogeneic = 23.5 +/- 2.33%) versus scaffold alone (46.8 +/- 11.8%) 4 weeks after surgery. Results of this study support syngeneic and allogeneic ASC acceleration of posterior lumbar spinal fusion in a rat model.

Callus formation and bark moisture as potential physical defenses of northern red oak,Quercus rubra, against red oak borer,Enaphalodes rufulus(Coleoptera: Cerambycidae)

AbstractThe red oak borer,Enaphalodes rufulus(Haldeman), is a native wood-boring beetle implicated as a major contributor to recent high levels of oak mortality in northern Arkansas. Northern red oaks,Quercus rubraL. (Fagaceae), were grouped into three classes of red oak borer infestation history based on crown condition and basal red oak borer emergence holes: class I (low infestation), class II (moderate infestation), and class III (high infestation). In 2004 and 2005, trees from each class were mechanically wounded and callus formation was measured after one year. Class I trees exhibited significantly greater callus formation than class III trees in both years. Monthly measurements in spring and summer of 2006 indicated significant differences in callus formation among classes, with class I trees healing over significantly earlier. Moisture was measured in bark samples removed 1 week and 4 weeks after initiation of three treatments: control, mechanical wounding, and artificial insertion of larvae. Moisture levels did not vary among infestation classes or treatments. This research indicates that bark moisture is likely not a defense against red oak borer, but that callus overgrowth may be a defense early in the second year of the life cycle in healthy trees.

Genotypic differences in callus formation and regeneration of somatic embryos in Cyclamen persicum Mill

This study was performed in order to check the applicability of a protocol for somatic embryogenesis in Cyclamen persicum and to compare the in vitro response of cultivars belonging to different cyclamen growth types and flower colours obtained from two breeders. One hundred ovules per plant were prepared from 32 tested F1 hybrid cultivars represented by five plants each. Callus induction monitored after 8 weeks varied between 42 and 85%. Variation occurred between replications and single plants of a cultivar. Consistency and colour of the developing calluses were diverse. Only in 1 cultivar out of the 32 tested no regeneration of somatic embryos was obtained. The regeneration rates varied from 0 to 65% among cultivars. In the group of midi-type cultivars the regeneration response was lower than that in mini and giganteum types. High regeneration rates were observed in cultivars with flamed flowers.

Effect of diclofenac sodium on union of tibial fractures in rats.

Nonsteroidal anti-inflammatory drugs are often used for 7 to 10 days after fracture because of their effects on bone metabolism. This study evaluated the effect of diclofenac sodium, administered at clinical dosage and duration, on bone union. Fifty-four male Wistar rats were randomly and equally divided into three groups: control, diclofenac 1 mg, and diclofenac 2 mg. Closed diaphyseal fractures were induced in the right tibias of all rats; the two diclofenac groups received intramuscular injections in the contralateral hips for 10 days. All animals were immobilized in circular casts on the upper thighs. Six rats in each group were sacrificed at weeks 2, 4, and 6, and bony union was evaluated clinically, radiologically, and histologically. At the end of 2 weeks, clinical examinations showed subjective differences between the two treated groups and control animals, with more stable callus formation in controls. Radiologic evaluation of the callus showed numeric, but not significant, differences between control and treated animals. At 4 and 6 weeks, clinical and radiologic findings were comparable among groups. Histologically, no significant differences in callus formation were evident at any evaluation.

Effect of nicotine on the rate and strength of long bone fracture healing.

Empirical clinical observation suggests that cigarette smoking had an inhibitory effect on long bone fracture healing, but this has not been proven scientifically. Forty female New Zealand White rabbits had midshaft tibial osteotomies performed and plated. These were divided randomly into two groups receiving either systemic nicotine or saline (placebo). Lateral radiographs were taken at 4, 6, and 8 weeks that showed a 17.2% average difference in callus formation between the two groups and a significant lag in formation of cortical continuity in the nicotine group. The rabbits were sacrificed 8 weeks after fracture, and healing was compared biomechanically. Three (13%) fractures showed no clinical evidence of union in the nicotine group, whereas all fractures in the control group healed. Biomechanical testing showed the nicotine exposed bones to be 26% weaker in three-point bending than were those exposed to placebo.

Optimizing Graft Union Formation between Sweetpotato (Ipomoea batatas) and Bush Morning Glory (Ipomoea carnea ssp. fistulosa) as a Prelude to Chimera Development

Bush morning glory (Ipomoea carnea ssp. fistulosa) and ornamental sweetpotato (Ipomoea batatas `Blackie') were grafted using various procedures. Lanolin pastes containing 3% BA, 3% NAA, and a mixture of 3% BA/3% NAA were tested as a means of promoting adventitious shoot development at the graft union. Excellent “take” was obtained with all graft types tested. The growth regulator treatments resulted in marked differences in callus formation at the wounded graft union. Lateral shoot development below the graft union also was affected by the growth regulator treatments. The highest quantity of callus was formed using the mixed paste, while BA enhanced lateral shoot formation below the union. Results indicate that in-vivo grafting of these two species may not be the best procedure for obtaining interspecific chimeras.

Blood Flow Measurement During Distraction Osteogenesis

The regional blood flow of 30 distraction segments in 27 patients was measured during distraction osteogenesis. There were three groups of patients. Group A consisted of seven patients with high grade malignant tumors who received chemotherapy preoperatively and postoperatively. Group B consisted of eight patients with low grade malignant and aggressive benign tumors, who all were treated without chemotherapy. Group C (the control group) consisted of 12 patients with nontumoral conditions. Using quantitative technetium scintigraphy, the regional blood flow within the distracted segment and surrounding soft tissues was measured. The measured radioisotope count was expressed as the ratio of the distracted site to the control site (blood flow ratio). The blood flow ratio for all the cases averaged 1.70 +/- 0.70. Group A had a lower blood flow ratio, which was statistically significant in comparison with the other two groups. The external fixation index showed no significant difference in callus formation among these three groups. No correlation was found between the blood flow ratio and external fixation index. Chemotherapy decreases regional blood flow, but with distraction osteogenesis the regional blood flow can be kept within the normal range or higher. Distraction osteogenesis may overcome the effects of chemotherapy by increasing blood flow.

Identification of callus types for long-term maintenance and regeneration from commercial cultivars of wheat (Triticum aestivum L.)

Immature embryos, inflorescences, and anthers of eight commercial cultivars of Triticum aestivum (wheat) formed embryogenic callus on a variety of media. Immature embryos (1.0-1.5 mm long) were found to be most suitable for embryogenic callus formation while anthers responded poorly; inflorescences gave intermediate values. Immature embryos of various cultivars showed significant differences in callus formation in response to 11 of the 12 media tested. No significant differences were observed when the embryos were cultred under similar conditions on MS medium with twice the concentration of inorganic salts, supplemented with 2,4-D, casein hydrolysate and glutamine. Furthermore, with inflorescences also no significant differences were observed. Explants on callus formation media formed two types of embryogenic calli: an off-white, compact, and nodular callus and a white compact callus. Upon successive subcultures (approximately 5 months), the nodular embryogenic callus became more prominent and was identified as 'aged callus'. The aged callus upon further subculture, formed an off-white, soft, and friable embryogenic callus. Both the aged and friable calli maintained their embryogenic capacity over many subculture passages (to date up to 19 months). All embryogenic calli (1 month old) from the different callus-forming media, irrespective of expiant source, formed only green shoots on regeneration media that developed to maturity in the greenhouse. There were no significant differences in the response of calli derived from embryos and inflorescences cultured on the different initiation media. Also, the shoot-forming capacity of the cultivars was not significantly different. Anther-derived calli formed the least shoots. Aged and friable calli on regeneration media also formed green shoots but at lower frequencies. Plants from long-term culture have also been grown to maturity in soil.

Effects of osmolality, cytokinin, and organic acids on pollen callus formation in Triticale anthers

Triticale anthers with pollen at middle to late uninucleated stages were cultured individually in Falcon micro test II tissue culture plates. The results indicate that when the anthers were cultured in the same growing conditions the differences in pollen callus formation among anthers from the first and second florets in the same spikelet were not statistically significant, whereas the differences in callus formation among anthers from different spikes (or plants) were statistically significant. These results suggest that comparisons of treatment effects should be made between samples consisting of anthers from the same spikelet only. Benzyl adenine (BA) and higher osmolality enhanced pollen callus induction, while a higher concentration of organic acids suppressed it. Under optimal conditions 31% of anthers formed callus, while the number of pollen calli per 100 seeded anthers was as high as 130. The pollen calli were able to develop into plants; however, the frequency was relatively low.

Varietal Difference in Callus Formation of Rice Seeds under Sterile Culture

The experiment dealts with the growth and morphology of callus in various varieties of rice belonging to Japonica and Indica types. The result indicates that Te-Tep has the highest growth rate among fifteen varieties used, reaching 3.13 g/5 seeds in fresh weight in 30 days at 30°C (table 2). There was observed the friable or compact callus (figs. 1 to 15). Te-Tep grows to the most compact callus, and Konan-senhas the highest growth rate among friable callus. According to an estimation of the diameter of nuclei with 100 cells of each callus, they indicates 6.3μ to 7.5μ wide in average value (table 3). It call be said that the nature of callus, friable or compact, growth rate, and size of the nuclei are independent to the types of variety, Japonica or Indica. It is interesting that the giant nuclei over 11.0μ appeared at a rate of 0.5 per cent of all nuclei observed. 5.5μ to 7.4μ of nuclei were 60.5 per cent. It was also observed that callus initiation and development in solutions of various concentrations of 2, 4-dichlorophenoxyacetic acid were different according to the varieties used, exception for Vialone nano which did not initiate callus at all at 1μM of 2, 4-D (table 1).