Basal Part Of Stem Research Articles

First Report of Bulb Rot Disease of Banana Caused by Klebsiella variicola in China.

Banana (Musa spp.) is an economically important fruit and food crop globally as well as in China. In March 2023, a bulb rot disease was observed on more than 20% of cultivated dwarf bananas in a plantation in Wuming County of Guangxi Province, a major hub of banana production in China. Infected plants showed crackles at the basal part of stem and were relatively dwarf, while yellowing of the leaves was not observed. When the rhizomes were cut open, water-soaked lesions with a yellow or black margin can be seen in the bulb. In severe infections, the internal tissue became dry or wet rot, and there was typical dark-brown cavity formation in the bulb. The rot was limited to the bulb. To isolate the causal agent, dissected diseased tissues (5×5 mm) were surface sterilized with 75% ethanol (30 s) and 2% NaClO (3 min), followed by three rinses with sterile water. The sterilized sections were soaked in 2 mL of sterile water and shaken for 5 min in a vortex oscillator. The suspension was streaked on Luria-Bertani (LB) agar medium, and incubated at 28℃ for 24 h. Single colonies were re-streaked three times to obtain purified isolation. Twelve pure bacterial cultures with similar morphology were isolated from three plants taken from the field. The bacterial colonies were yellowish white, mucoid, round, and raised with translucent surfaces on the LB agar plate. Three strains Gxkv1, Gxkv2 and Gxkv3 were selected for further analyses. The 16S rDNA gene (GenBank Accession OR461756, PP094726 and PP109349) were amplified using primer pair 27F/1492R (Frank et al. 2008). Comparing 16S sequences against GenBank showed 99.86%-100% sequence identity to Klebsiella variicola strain (MZ475068) for the three isolates Gxkv1 (1,398/1,398 bp), Gxkv2 (1,398/1,396 bp) and Gxkv3 (1,398/1,398 bp). A multilocus phylogenetic analysis was conducted by neighbor-joining method (1,000 bootstrap values) based on three housekeeping gene sequences of gyrA (GenBank Accession No. OR515493, PP105747, PP105748), rpoB (OR515494, PP105751, PP105752 ) and infB (OR515495, PP105749, PP105750) genes which were amplified by gyrA-A/gyrA-C, CM31b/CM7 and infB867F/infB1819R primer sets, respectively (Rosenblueth et al. 2004). The results of phylogenetic analysis showed the three strains belong to the K. variicola clade. A pathogenicity test was conducted on six healthy 3-month-old dwarf banana plants by spraying 10 mL of bacterial suspensions of Gxkv1 (108 CFU/mL) into the rhizome which wounded with a sterilized needle; another six healthy control plants were sprayed with 10 mL of sterile water. Following inoculation, the plants were placed in a greenhouse at 28-32°C. After 30 days, all inoculated plants showed symptoms similar to those observed in the field, while the control plants remained healthy. Bacteria were successfully reisolated from the symptomatic tissues and identified to be K. variicola by PCR mentioned above. K. variicola has been reported to cause rhizome rot of banana in India (Loganathan et al. 2021), and to cause plantain soft rot in Haiti (Fulton et al. 2021). Besides, previous reports from China only showed K. variicola causing banana sheath rot (Fan et al. 2015, Sun et al. 2023). To our knowledge, this is the first report of bulb rot disease of banana caused by K. variicola in Guangxi Province, China. This finding will provide important information for studying the epidemiology and management of this pathogen.

Occurrence of stem blight and fruit rot caused by Phytophthora capsici on Chinese cucumber (Trichosanthes kirilowii) in China.

Chinese cucumber, Trichosanthes kirilowii Maxim, is a perennial liana plant belonging to the Cucurbitaceae family and is an important traditional medicine in Chinese herbalism. The root, fruit and seed possess the medicinal value, and also the seeds are edible (Zhang et al. 2019). With increasing demand, the wild resource was domesticated and has been planted in China. Diseases of T. kirilowii have become more prominent with the expansion of cultivated area and have caused the yield reduction (Zhang et al. 2014). The general disease field has caused a yield reduction of 10% -30%, even up to 80% seriously. Since 2017, fields in Luan city, Anhui province exhibited 10 to 30% of plants with stem blight and fruit rot. The two-week seedlings were infected at the basal part of stem and showed water-soaking, then damping off. In older plants, it is common to see stem blight with brown-to-black lesions, stunted growth, and most diseased plants eventual death. On rot fruit, the symptom of water soaked lesions was firstly observed, and then with white mold, eventual rot. More than 60 samples of symptomatic stems or fruit were collected from Luan and Hefei, Anhui province during April to October 2017. The symptomatic tissues were washed, disinfested with 0.5% sodium hypochlorite for 30 s, rinsed twice in sterile water for 1 min, dried and incubated on V8-juice amended with 50μg ml-1 of ampicillin and rifampicin at 25°C. Based on morphological characteristics, more than 80% of the total 98 isolates generated were similar on the level of morphology, and preliminarily identified as Phytophthora species (Erwin and Ribeiro 1996). Three isolates were selected randomly to further observe and identify up to species level. The isolates produced abundant, aerial, white mycelia on V8 agar plates. Sporangia were produced on sporangiophores in 10% V8 liquid culture medium after 4 days at 25°C, mainly obovoid with one papilla, 38.8 to 50.4 μm× 22.8 to 33.5 μm in size. The single mature sporangium immersed in water quickly released 20 to 40 biflagellate motile zoospores. The isolates were further confirmed by amplification and sequencing of two conserved markers, the internal transcribed spacer (ITS) region and cytochrome c oxidase subunit I (COI) region with primers ITS1/ITS4 (White et al. 1990) and OomCoxILevup/Fm85mod (Robideau et al. 2011), respectively. The GenBank Accession Nos. were MN368092, and MN369544 for ITS and COI, respectively. The BLAST search results showed 100% similarity with ITS sequences (KF700090, KC438376) and COI sequences (MH136864, AY129166) of Phytophthora capsici isolates in Genbank. Koch's postulates were performed by testing the pathogenicity of the sequenced isolate on the Chinese cucumber (cv. 'Wanlou9'). On 1-month-old plants, a flap of bark was cut with a sterile scalpel, and the 2×2 cm plug of 5-day-old mycelium was inserted. The flap was then closed and sealed with Parafilm. The agar plug was treated in the same manner as the inoculated plants as the controls. And also, the intact fruit (one month old) was inoculated with 10 μL of zoospore suspension (2 × 105 zoospore/ml) and kept in growth chamber at 25 °C, with 80% relative humidity, and the control was treated with 10 μL of sterile distilled water. Three days after inoculation, the stems and the fruit inoculated with mycelium and zoospores showed water-soaked lesions. After 10 days, the symptoms on the tissues resembled those observed in the field. No symptoms were detected on the controls. P. capsici was reisolated from the diseased tissues but not from the control. This combination of data confirmed that the pathogen was P. capsici. To our knowledge, this is the first report of P. capsici causing stem blight and fruit rot on Chinese cucumber in China.

Ecosystem Engineering by Plants on Wave-Exposed Intertidal Flats Is Governed by Relationships between Effect and Response Traits.

In hydrodynamically stressful environments, some species—known as ecosystem engineers—are able to modify the environment for their own benefit. Little is known however, about the interaction between functional plant traits and ecosystem engineering. We studied the responses of Scirpus tabernaemontani and Scirpus maritimus to wave impact in full-scale flume experiments. Stem density and biomass were used to predict the ecosystem engineering effect of wave attenuation. Also the drag force on plants, their bending angle after wave impact and the stem biomechanical properties were quantified as both responses of stress experienced and effects on ecosystem engineering. We analyzed lignin, cellulose, and silica contents as traits likely effecting stress resistance (avoidance, tolerance). Stem density and biomass were strong predictors for wave attenuation, S. maritimus showing a higher effect than S. tabernaemontani. The drag force and drag force per wet frontal area both differed significantly between the species at shallow water depths (20 cm). At greater depths (35 cm), drag forces and bending angles were significantly higher for S. maritimus than for S. tabernaemontani. However, they do not differ in drag force per wet frontal area due to the larger plant surface of S. maritimus. Stem resistance to breaking and stem flexibility were significantly higher in S. tabernaemontani, having a higher cellulose concentration and a larger cross-section in its basal stem parts. S. maritimus had clearly more lignin and silica contents in the basal stem parts than S. tabernaemontani. We concluded that the effect of biomass seems more relevant for the engineering effect of emergent macrophytes with leaves than species morphology: S. tabernaemontani has avoiding traits with minor effects on wave attenuation; S. maritimus has tolerating traits with larger effects. This implies that ecosystem engineering effects are directly linked with traits affecting species stress resistance and responding to stress experienced.

None-Watering and Tube-Protecting Planting Technique for <italic>Haloxylon ammodendron</italic> under Desert and Its Extension

<italic>Haloxylon ammodendron</italic> has been one of the preferred plants that are used for the ecological recovery and restoration of the desert in China, but its seedlings have a very low percentage of seedling survival (￡10%) and grow slowly under none-watering condition in the desert areas, which is a pivotal limiting factor for its utilization. Besides soil drought, sandwind, and small animal gnawing, our recent research results unveiled that the high desert surface layer (0-2 cm) temperature (350℃) around the basal part of stem of <italic>Haloxylon ammodendron</italic> seedlings also is one of the important limiting factors, but this limiting factor is often neglected in the process of practice. Based on this discovery, we invented a new none-watering and tube-protecting planting technique for<italic> Haloxylon ammodendron</italic>. After several years proof-test in many desert environments, this new planting technique has been found to be suitable for utilization in the desert habitats with higher ground water level or abundant wet sand layer, including drifting or semi-drifting sand dunes, especially for fixed dune, gobi, and soil desertification. It has the following characteristics and advantages: protecting <italic>Haloxylon ammodendron</italic> seedlings from the damage of high desert surface layer temperature, sandwind, small animal gnawing, etc.; easy to operate; needing no watering; suitable for fall and spring planting, as well as direct seeding and transplantation. As a result, it can efficiently increase the percentage of seedling survival (averagely more than 70%) and annual growth (more than 20%) of <italic>Haloxylon ammodendron</italic>. Additionally, it is also found to be suitable for the planting or cultivation of other desert plants. Now the new planting technique is in widespread demonstration and extension in the desert areas of Xinjiang, Inner Mongolia, and Gansu.

Adaptations in Response to Salinity in Safflower Cv. Bhima

Effect of increasing levels of NaCl and Na2SO4 on mineral content in various organs of safflower (Carthamus tinctorius L.) cv. Bhima was investigated at flowering. Results revealed that Dry Matter (DM) per plant decreased with increasing levels of NaCl. DM increased at low levels and decreased at all higher levels of Na2SO4 at flowering and maturity. Plants completed life cycle upto ECe 7.5 mS cm-1 of chloride and ECe 10.0 mS cm-1 of sulphate salinity. Plants tolerate all levels of chloride and higher levels of sulphate salinity by storing toxic minerals in roots and basal part of stem and by translocating essential elements to the leaves indicating presence of regulatory mechanism at the junction of root and stem; within the stem and in between the stem and leaves in safflower.

Effects of clone and cutting traits on shoot emergence and early growth of willow

To assess if size differences between plants in establishing willow stands may be caused by differences between cuttings prior to planting, plant response (survival, sprouting in terms of emergence time and shoot number, and growth in terms of shoot size, weight and leaf area) was quantified as a function of clone, original position on shoots from which cuttings are derived, cutting length, cutting diameter, and field storage time. Longer and thicker willow cuttings developed more and taller shoots and displayed a higher biomass production than shoots from short and thin cuttings. Cuttings derived from apical positions along shoots displayed for a given diameter a higher shoot biomass production than cuttings derived from the more basal parts. The effect of position was related to differences between cuttings with regard to phenology, bud burst for cuttings from high positions having progressed further after a fortnight than buds on cuttings from basal stem parts. A two week field storage of shoots prior to planting led to a decrease in early biomass production. We conclude that the planting system based on the use of entire shoots comprises a considerable amount of pre-emergence variation in the cuttings, which underlies size variation development during early establishment of willow plantations. To obtain a faster and more even establishment of willows, we recommend the use of larger and more even-sized cuttings, and a shortest possible field storage time.

Chemical screening for promotion of adventitious root formation in Eucalyptus globulus

Eucalyptus globulusis one of the most profitable trees for pulp and paper industries due to its fast growth and short harvesting cycle. This species is easily pulped with high yield, and its fiber qualities are among the best for paper production. However, it is difficult to vegetatively propagate E. globulus.So far, we have developed “photoautotropic culture method” that promotes rooting percentage by feeding approximately three times higher level CO2 level (1000 µmol mol–1) and suitable culture condition [1]. However, several lines showed poor rooting percentage even in the higher CO2 conditions. Therefore, it was necessary to develop novel method for promotion of adventitious root (AR) formation in E. globulus. First, we measured endogenous levels of 20 kinds of hormones such as abscisic acid, auxins, cytokinines and gibberellins, at basal part of stem of easy-rooting line and poor-rooting line by UPLC-ESI-qMS/MS. As a result, the Indole-3-acetic acid (IAA) level of easy-rooting line was two times higher than that of the poor-rooting line, suggesting that endogenous IAA level may regulate ability of AR formation. Next, we focused on the cytochrome P450s that are involved in a vast array of reactions of many different metabolic pathways. Several triazole-containing chemical compounds have previously been shown act as efficient inhibitors of cytochrome P450 monooxygenases. A chemical library of triazole derivatives to find chemicals which have the effect of promoting AR formation was screened. Consequently, five compounds effectively promoted AR formation. Finally, we investigated how these chemicals affected the growth of Arabidopsis thaliana. Arabidopsis seedlings were grown on agar medium containing 1 μM selected chemicals. One of the selected chemicals, MA65 increased the number of roots in wild-type Arabidopsis seedlings and this phenotype was similar to a mutant superroot2 (sur2) [2]. The SUR2 gene encodes the cytochrome P450 CYP83B1, a modulator of auxin homeostasis. The amounts of endogenous IAA in 14-d-old Arabidopsis grown in the presence of 1 mM MA65 were analyzed. The IAA content was increased two-fold in the presence of MA65 as compared with untreated Arabidopsis. In addition, 1.0 cm explants of Arabidopsis stems were incubated for 7 d on MS medium containing 1 mMMA65. Stimulation of an AR formation was observed as compared to untreated samples. Taken together, MA65 may increase endogenous IAA level in a plant cell and promotes an AR formation.

Tenuisa frasnianagen. et sp. nov., a Plant of Euphyllophyte Affinity from the Late Devonian of China

Tenuisa frasniana gen. et sp. nov. is reported from the Late Devonian (Frasnian) Hunan Province of South China. Its axes are naked and narrow. Fertile stem is pseudomonopodial in branching and bears distichous lateral units. Fertile lateral units are subopposite and pseudomonopodial in the proximal part of stem, while they are alternate and isotomous two to four times in the distal part. They have tiny terminal sporangia that are paired and fusiform and that possess pedicels. Sterile ultimate units are dichotomous and terminate in tips recurving oppositely. Tenuisa resembles Psilophyton in pseudomonopodial fertile stem with alternate and dichotomous lateral units terminated by paired and vertically elongate sporangia. However, fertile lateral units are subopposite and pseudomonopodial on the basal part of stem, sporangial pedicels are present, and neither sporangial pairs nor sporangia themselves are twisted. This new plant differs from iridopteridalean cladoxylopsids mainly in the absence of whorled laterals and axial spines, and it differs from pseudosporochnalean cladoxylopsids in the absence of digitate lateral branches and the presence of sterile ultimate units with recurved tips. Because of these morphological differences and a lack of anatomical information, Tenuisa frasniana is currently left as incertae sedis within Euphyllophytina (sensu Kenrick and Crane).

Complete Resistance by Carnation Cultivars to Fusarium Wilt Induced by Fusarium oxysporum f. sp. dianthi Race 2.

The response of two carnation (Dianthus caryophyllus) cultivars, Arbel and Scarlette, to Fusarium wilt induced by Fusarium oxysporum f. sp. dianthi race 2 was determined in experiments conducted in an infested field and using artificially inoculated plants grown in a net-house. In six field experiments conducted from 1989-90 to 1995-96, and including more than 200 different cultivars, Arbel and Scarlette were the only ones that remained symptomless. The responses of the other cultivars varied markedly, but even those known to be highly resistant, Eveline and Novada, were frequently diseased. In the net-house tests, Arbel and Scarlette were compared with cultivars that ranged in their response to Fusarium wilt from highly resistant to highly susceptible. Due to the conducive conditions for Fusarium wilt prevailing in these tests, disease progressed rapidly, and by the end of the experiments all cultivars except Arbel and Scarlette were severely diseased (incidence of 81.2 to 100%); Arbel and Scarlette remained symptomless. The pathogen did colonize the basal stem parts of all cultivars, including Arbel and Scarlette. The number of colony-forming units (CFU) recovered from the basal stem parts was 105 CFU/g of stem in the other cultivars, 103 CFU/g in Scarlette, and 50 CFU/g in Arbel. Results of our study suggest that Arbel and Scarlette exhibit a novel type of resistance to Fusarium wilt induced by F. oxysporum f. sp. dianthi race 2.

Analysis of Factors Concering Bleeding Rate from the Basal Part of Stem in Rice Plants.

水稲茎基部からの出液は, 根の呼吸に関連する生理活性と関係していると考えられるが, 同一の齢でも出液速度が大きくばらつくことが指摘されている. そこで, 出液の測定条件を検討し, 出液に関与する要因を明らかにして, 出液速度で生理活性を把握できるかどうかを検討した. 同一個体内で出液を採取する茎以外の茎に葉が着生していると, それの蒸散のために出液量が減少した. したがって, 出液を採取する際には, 測定個体のすべての茎を切除する必要を認めた. 切断部の茎断面積と1茎当たり出液速度とは高い正の相関関係があり, 断面積の大きい茎, すなわち太い茎は茎断面積当たりの出液速度も高い値であった. 地温が7℃から29℃までの範囲では, 出液速度は地温に伴って指数関数的に増加し, その温度係数(Q10)は2.2で, 根の呼吸速度の温度係数とほぼ同じ値であった. 上記の測定条件を考慮したうえで, 穂ばらみ期以降の根の呼吸速度と出液速度との関係を検討した結果, 両者の間には高い正の相関関係が認められた. これより, 根の生理活性が重要な問題となる登熟期では, 出液速度から根の生理活性を推定することができ, 出液速度の測定は, 根の診断のうえで有効で簡便な手法のひとつとしてあげることができる.

Mineral nutrition and transport in xylem and phloem ofBanksia prionotes(Proteaceae), a tree with dimorphic root morphology

Xylem sap of proteoid roots, lateral roots, sinker root and age classes of trunk segments, and phloem sap of mid-trunks were collected from trees of Banksia prionotes (Proteaceae) in native habitat on highly impoverished sands in south-western Australia. Proteoid roots were major exporters of phosphate, K + and amino acids during the wet winter season and showed in vitro nitrate reductase activity during periods of soil nitrification. Other parts of the root served as general sources of Na + , Cl - , Mg 2+ , Ca 2+ , and SO 4 2- . Lateral root xylem sap was more concentrated in virtually all solutes than that of sinker roots, even during the dry summer following senescence of proteoid roots. Gradients in xylem sap concentration up the main trunks suggested lateral abstraction and storage of incoming phosphate in basal stem parts during winter and a subsequent release to the xylem in summer. Phloem sap was many times more concentrated in nutrient ions than xylem sap, and, like xylem sap, showed unusually low K + and H 2 PO 4 - relative to Na + , Cl - and SO 4 2- , suggesting a sparing role of the latter three ions in meeting ionic requirements of transport. Amino acid analyses showed higher overall concentrations in phloem than xylem sap, but much lower proportions of total amino N as glutamine and asparagine in the former sap. This suggested utilization of xylem-derived amide N by leaves for growth and synthesis of phloem-mobile amino acids.

Nitrate movement in xylem of lucerne plants

Nitrate content in lucerne stems and leaf blades immersed by cut ends in distilled water or in KNO3 solution increased with the increase in KNO3 concentration and with the duration of exposure under irradiance of 100 or 230 W m-2 PAR. The nitrate content increased from basal stem parts to apical stem parts and leaves. Nitrate was transported mainly with transpiration stream. Some flow variations occurred in stems causing time changes in nitrate content in different parts of stems.

Effect of monoethanolamine on growth and biomass formation of rye and barley

Monoethanolamine (EA) applied to rye and barley as a foliar spray increased the biomass and grain yield formation of tillers (up to 14%) and promoted the growth of the basal stem parts (up to 17%). The increased production of tillers and the stimulated growth of basal internodes were associated with a higher nitrogen level in these plant parts. A sufficient nitrogen supply was an essential requirement for increasing the yield of tillers by EA.

Detection of tobacco rattle virus in different parts of tulip by ELISA and cDNA hybridisation assays

Different parts of tulips cv. Apeldoorn were assayed for the presence of tobacco rattle virus (TRV) by means of ELISA, cDNA hybridisation and immuno-electron microscopy. Assays were periodically performed during the growing season and upon storage of the bulbs, During the growing season in the field the relative TRV concentrations detected by ELISA and cDNA were highest mainly in the basal stem-parts and basal leaf-parts, respectively. When, during storage, infected bulbs were divided into a number of sections, TRV could be detected only in some of the sections, irrespective of the test used. However, nearly all sprouts of infected bulbs, stored at 5°C for 7 months, appeared to contain detectable amounts of TRV upon testing with ELISA and cDNA. Thus, testing of sprouts may offer a possibility to develop a routine test for TRV in tulip bulbs in due course. Verschillende delen van tulp cv. Apeldoorn werden getoetst op de aanwezigheid van tabaksratelvirus (TRV) met behulp van ELISA, cDNA-hybridisatie en immuno-elektronemicroscopie. Tijdens het groeiseizoen en de bewaring van de bollen werden regelmatig toetsingen uitgevoerd. Gedurende het groeiseizoen op het veld werden de relatief hoogste TRV concentraties voornamelijk gevonden in het basale deel van de stengel en het okselgedeelte van het blad met respectievelijk ELISA en cDNA-hybridisatie. TRV bleek gelokaliseerd aanwezig te zijn in een of meer stukjes van een gedeelde bol, onafhankelijk van de gebruikte toetsmethode. Bijna alle spruiten van geinfecteerde bollen die gedurende 7 maanden bij 5°C bewaard waren, bleken bij het toetsen met behulp van ELISA en cDNA aantoonbare hoeveelheden van TRV te bevatten. Het toetsen van spruiten biedt de mogelijkheid te zijner tijd een routinetoets voor TRV in tulpebollen te ontwikkelen.

Correlative Effects of Root and Basal Part of Stem upon the Content of Cytokinins in Leaves of Bryophyllum crenatum

Summary An unilateral transverse incision in the central part of Bryophyllum crenatum stem below one of opposite leaves released this leaf from correlative-promoting effects of the root and the basal part of stem. This resulted in a decreased level of endogenous cytokinins in the leaf sbove the incision (i.e. facing the opposite control leaf) within 24 h after the incision; however, the level increased again within 7 d, and marginal buds were formed within a period of 35 d.

Effect of Ethylene on Aerenchyma Development

When applied to a part of stem or basal part of stem and root system, 1 ppm ethylene induced lysigenous aerenchyma development in the stem cortex of Helianthus annuus, Lycopersicon esculentum, and Phaseolus vulgaris. Local application of ethylene to a part of stem significantly increased the activity of cellulase in that part of stem in the above three species. Pretreatment of a part of stem with 100 ppm AgNO3 counteracted the effects of ethylene which was subsequently applied to the part of stem, completely suppressing aerenchyma development and highly significantly reducing cellulase activity in Helianthus annuus. These results support the earlier proposal that the deficiency of oxygen in waterlogged plants triggers the anaerobic stimulation of ethylene production, which in turn increases the cellulase activity leading to aerenchyma development.

EFFECT OF ETHYLENE ON AERENCHYMA DEVELOPMENT

When applied to a part of stem or basal part of stem and root system, 1 ppm ethylene induced lysigenous aerenchyma development in the stem cortex of Helianthus annuus, Lycopersicon esculentum, and Phaseolus vulgaris. Local application of ethylene to a part of stem significantly increased the activity of cellulase in that part of stem in the above three species. Pretreatment of a part of stem with 100 ppm AgNO3 counteracted the effects of ethylene which was subsequently applied to the part of stem, completely suppressing aerenchyma development and highly significantly reducing cellulase activity in Helianthus annuus. These results support the earlier proposal that the deficiency of oxygen in waterlogged plants triggers the anaerobic stimulation of ethylene production, which in turn increases the cellulase activity leading to aerenchyma development.

Characteristics of the Bark Splitting Injury of Young Tea Plant and Weather Condtion Influencing this Frost Injury

In recent years, the bark splitting injury has occurred frequently both on cuttings in nursery and on young plants in tea gardens at southern districts of Kyushu.In order to clarify the characteristics of the bark splitting injury, the various field conditions and the climatic factors easy to cause it were investigated.1. The bark splitting injury occurred on the basal part of stem of both cuttings and young plants up to two-year-old was chiefly observed at the first frost near the ceasing time of the autumn growth.The occurring mechanism of this injury is expressed as that the bark of stem near the ground surface splits open lengthwise owing to ice formed between sapwood and bark under the continuous freezing by the effective low temperature (about-3 to-5°C). The bark split recovers with growth of the callus in case of the slight damage but if it is severe, the plant weakens gradually and will finally die.2. From the observations of recovering process after the injury, the symptoms of the occurrence of the injury were classified in three different types : a) the bark of stem near the ground surface splits lengthwise, b) the bark separetes from sapwood without the bark split and c) the cambial tissue becomes brownish without the bark split.In the case of b) and c), the injury remains as a frost-ring on the stem.3. Both the cold injury during midwinter and the bark splitting injury in late autumn or early winter cause the young plants to be seriously damaged. The reasons for the above are as follows : 1) the root systems of young plant are poor, 2) the stems of young plant are scarcely protected from low temperature by their own leaf layer and 3) the acquiring time of the herdiness of young plants is late because they grow actively till late autumn.4. The minimum air temperature at about five centimeter above the straw mulch on fine days in Chiran, where the injury occurred frequently and severely, was 6 °C lower than that of Makurazaki, where no injury occurred, while the mean and maximum air temperature of both sites were almost same.So the primary climatic factor responsible for the occurrence of the bark splitting injury in Chiran is assured to be sudden down of the minimum air temperature at the first frost in autumn.5. The minimum air temperature in the field mulched with the straw was lower than that of non-mulched field, and the mulching kept the soil temperature high in night. These effects were remarkably great on fine day. Therefore, it was considered that the straw mulch promoted the bark splitting injury because of the high soil moisture, the high soil temperature and the low air temperature near the mulch surface at the frosty night.And then, it was also pointed out that the average of the minimum temperature for ten days before the first autumn frost was higher in the injury years and places than in the normal ones.