Shoot Characteristics Research Articles

True-to-type confirmation of 20 unknown grapevine accessions at a grape germplasm collection in Split, Croatia

Twenty unknown accessions maintained in the field collection of the Institute for Adriatic Crops and Karst Reclamation (IAC), Split, Croatia, were identified. Morphological validation was done using standard OIV descriptors encompassing shoot, leaf and cluster characteristics. A standard set of nine simple sequence repeats (SSRs) were amplified and genetic diversity indices were calculated. The allelic data of the 20 unknown genotypes were compared with reference SSR profiles from the European database Vitis International Variety Catalogue (VIVC; http://www.vivc.de/) and grape germplasm collection of the UK. Three accessions proved to be mislabelled and were identified as known European grapevine cultivars (‘Blaufraenkisch’, ‘Chardonnay’ and ‘Merlot’), two unknown accessions showed identical genotypes matching ‘Chasselas blanc’ and ‘Chasselas rose’, while 12 unknown genotypes confirmed their declared status. Finally, three unknown genotypes of interspecific crosses (‘Ljana’, ‘Original’, ‘Nero’) were not found in VIVC database or in published literature, revealing SSR profiles that are novel to the best of our knowledge. This study presents necessary information to establish cultivar status (true to type) of 20 unknown accessions from the IAC Split grape collection.

Hydroponics: An Alternative Method for Root and Shoot Classification on Sugarcane Genotypes

A hydroponic system was considered to be an appropriate method for root investigations, particularly if the method can be established as a screening technique to classify differences in root traits among sugarcane lines. The aim of the research was to classify root and shoot characters of sugarcane lines grown under hydroponic conditions and to investigate their correlation with the field measurements. Hydroponic and field tests used a randomized complete block design (RCBD). Eight elite sugarcane lines were assigned as treatments. Shoot and root traits were measured at 3 months after transplanting in the hydroponic experiment, and field trial measured root length density (RLD) at 4 months after planting. Root and shoot traits under the hydroponic system showed significant differences among sugarcane lines. KK3 had a high root surface area, root volume, root length and root dry weight and TBy27-1385 demonstrated a high stem height and stem dry mass. Moreover, root dry weight, root volume and root surface area positively correlated with shoot dry mass. Positive correlation was exhibited between root traits such as dry weight of root and root length derived from hydroponic studies and RLD derived from field conditions.

Effects of LPDBD Plasma and Plasma Activated Water on Germination and Growth in Rapeseed (Brassica napus)

The study deals with the effect of low pressure dielectric barrier discharge (LPDBD) plasma and plasma activated water (PAW) produced with Ar, O2 and Air on germination and growth in rapeseed. Although H2O2 concentration showed no significant changes, α‑amylase activity (germination inducer) significantly increased in seeds due to LPDBD plasma. In addition, the activity of SOD and CAT was significantly induced in seeds of rapeseed treated with PAW. Rapeseed plants grown from the LPDBD plasma treated seeds showed significant improvements in shoot characteristics, chlorophyll synthesis, total soluble protein and sugar concentration compared to controls. Interestingly, plasma treated plants also showed no significant variations of H2O2 in tissue(s) which is supported by the biochemical and molecular evidence(s) of antioxidant enzymes. Plants exhibited a significant increase in tissue APX and CAT activities along with BnAPX and BnCAT expression(s) in roots when seeds were treated with LPDBD Air/O2 and PAW O2. This suggests that LPDBD plasma might have been involved with elevated level of reactive oxygen species, which was tightly controlled through the upregulation of APX and CAT activities and thus trigger the growth and development in rapeseed plants. These findings reveal the role and mechanisms of LPDBD technique facilitating germination and growth in rapeseed plants.

Biotic and Abiotic Conditions Can Change the Reproductive Allocation of Zostera marina Inhabiting the Coastal Areas of North China

The relationships between reproductive allocation and different factors have been widely recognized for terrestrial plants, but scarcely for marine angiosperms. Focusing on the seagrass Zostera marina, we examined the change in biomass when it was partitioned to growth, vegetative propagation and reproductive allocation of Z. marina. We also evaluated the relationships between reproductive allocation and biotic and abiotic conditions in the coastal areas of north China. The results indicated that the reproductive allocation of Z. marina at the levels of genet, shoot and spathe was positively correlated with shoot characteristics such as height and biomass (P < 0.01), but was negatively correlated with branch number and leaf number per genet (P < 0.01). In addition, the allocation was also affected by other abiotic factors such as water column phosphate concentration (P < 0.05) and sediment total petroleum (P < 0.01). These findings indicated that both biotic and abiotic conditions significantly influenced the reproductive allocation of Z. marina, which may affect further the population dynamics.

Effect of plant growth regulators on rooting and shooting of Indian sarsaparilla (Hemidesmus indicus L.)

Indian sarsaparilla (Hemidesmus indicus L.) is an important medicinal plant widely used in Indian systems of medicine as an antipyretic, blood purifier and refrigerant. It is under the list of endangered species in India due to the indiscriminate collection and utilization. To bring the plant under commercial cultivation, standardization of propagation through cuttings with different plant growth regulators was attempted in this study. The cuttings (20 cm length with 3–4 nodes) were treated with different plant growth regulators viz., IAA (1000, 1500 and 2000 ppm), IBA (1000, 1500 and 2000 ppm) and GA3 (1000, 1500 and 2000 ppm) for three to five seconds and subjected to rooting under mist chamber condition. Observations on days taken for rooting, number of roots per cutting, length of the root, fresh weight of the roots per cutting, dry weight of roots per cuttings, days taken for sprouting, shoot length, number of shoots, fresh shoot weight and dry shoot weight were recorded. Among the different treatments, cuttings treated with IBA 1500 ppm registered early rooting (26 days), increased root length (27.6 cm), highest number of roots (64) and fresh root weight (1.1g). The shoot characters like early sprouting (20 days), highest shoot length (43.5 cm), highest number of shoots (48), highest fresh shoot weight (3.1g) and dry shoot weight (1.1g) were also recorded in the treatment IBA 1500 ppm. Thus, this present investigation revealed that, the cuttings of Indian sarsaparilla treated with IBA 1500 ppm under mist chamber condition had significant effect on all root and shoot parameters and it was found to be the most appropriate concentration for the rooting of cuttings.

Salicylic acid mitigates hyperhydricity in newly developed potato shoots through reduced oxidation

Hyperhydricity is a metabolic disorder of plants raised in tissue culture. In shoot cultures of potato (Solanum tuberosum L. ‘Atlantic’), hyperhydricity is induced by the synthetic cytokinin 6-benzylaminopurine (BA). Withdrawing BA from Murashige and Skoog (MS) medium and replacing it with salicylic acid (SA) restores lateral growth in mildly hyperhydric shoots. To evaluate the role of SA in reducing the extent of hyperhydricity in newly developed potato shoots, the physiological characteristics and enzyme activities of normal, hyperhydric, and SA-treated potato shoots were analyzed and compared. The results showed that the lower dose of SA (1 μmol·L−1) was more effective than the higher dose (100 μmol·L−1) at ameliorating the phenotypic and physiological characteristics of hyperhydric potato shoots. The SA-treated potato shoots did not significantly differ from normal potato shoots in term of phenotype and physiology. Oxidative stress in the hyperhydric potato shoots was alleviated by the SA-induced increases in free putrescine and spermine, glutathione, and increased activity of superoxide dismutase, catalase, and glutathione reductase, all of which were promoted by reactive oxygen species. The results also demonstrated that SA mitigates mild hyperhydricity and could help optimize potato propagation in tissue culture.

Detection and analysis of large‐scale WT blade surface cracks based on UAV‐taken images

Aiming at the high cost and the poor working environment of the detection of large-scale wind turbine (WT) cracks, an analytic detection method based on blade images taken by unmanned aerial vehicles (UAVs) is proposed in this study. For the characteristics of the UAV shooting and the location of the WT, the pre-processing of motion blurring, image noise reduction and image enhancement is used to make the target area and crack details more clear and complete. Then, a crack analysis method based on the grey-scale value is proposed, taking into account the distribution, severity and development trend of the cracks, so that the blind area in the daily detection of the WT can be reduced, the subsequent maintenance of the WT blade is made more accurate, and essentially the operation and maintenance costs be reduced considerably.

SSR-based genetic linkage map construction in pistachio using an interspecific F1 population and QTL analysis for leaf and shoot traits

Pistachio is one of the most commercially important nut trees in the world. To characterize the genetic controls of horticultural traits and facilitate marker-assisted breeding in pistachio, we constructed an SSR-based linkage map using an interspecific F1 population derived from a cross between the cultivar “Siirt” (Pistacia vera L.) and the monoecious Pa-18 genotype of Pistacia atlantica Desf. This population was also used for the first QTL analysis in pistachio on leaf and shoot characters. In total, 1312 SSR primers were screened, and 388 loci were successfully integrated into parental linkage maps. The Siirt maternal map contained 306 markers, while the “Pa-18” paternal map included 285 markers along the 15 linkage groups. The Siirt map spanned 1410.4 cM, with an average marker distance of 4.6 cM; the Pa-18 map covered 1362.5 cM with an average marker distance of 4.8 cM. Phenotypic data were collected during the growing seasons of 2015 and 2016 for four traits: leaf length (LL), leaf width (LW), leaf length/leaf width ratio (LWR), number of leaflet pairs (NLL), and young shoot color (YSC). A total of 17 QTLs were identified in the parental maps. Four QTLs for LL and LW were located on LG2 and LG4, while four QTLs for LWR ratio on LG13 and LG14, two QTLs for NLL and two QTLs for YSC were on LG7 and LG9, respectively, with similar positions in both parental maps. The SSR markers, linkage maps, and QTLs reported here will provide a valuable resource for future molecular and genetic studies in pistachio.

Supercritical carbon dioxide extraction of triacontanol from green tea leaves and its evaluation as an unconventional plant growth regulator for spinach tissue culture

Abstract Triacontanol (TRIA) is a naturally synthesized non-conventional plant growth regulator (PGR) that can substitute synthetic PGRs, which are deleterious for human health and environment. TRIA was isolated from green tea leaves using Soxhlet and supercritical fluid extraction (SCF). Maximum extraction of 142 mg/kg (without alkali treatment) and 179 mg/kg (with alkali treatment) was achieved using pet-ether (60–80 °C) by Soxhlet extraction for 24 h. This was used as a standard against which the yield obtained by SCF was expressed relatively. The conditions for maximum extraction of TRIA using SCF were arrived by calculating the solubility parameters of TRIA and carbon dioxide using the Hildebrandt solubility equation. The results predicted therefrom were validated experimentally. SCF at 400 bar/60 °C/180 min gave a maximum relative extraction efficiency of 349% as compared to Soxhlet extraction without alkali treatment. TRIA thus obtained was checked for its potential as a PGR for spinach tissue culture and was compared to synthetic PGRs, TRIA and Indole acetic acid (IAA-100 µM). Medium supplemented with 5 nM TRIA increased shoot characters such as total shoot length and the number of leaves. The maximum dry weight of plant was observed in 2.2 µM TRIA containing medium. Plant nutrients like chlorophyll, carotenoids and ascorbic acid were also analyzed. Maximum yield of 84 mg/100 g ascorbic acid was obtained in plantlet grown in 2.2 µM TRIA while chlorophyll and carotenoids remained unaffected. SCF extracted TRIA showed results comparable to that of standard TRIA and IAA.

Mechanisms and Signaling Associated with LPDBD Plasma Mediated Growth Improvement in Wheat

This study investigates the effect and mechanisms of low pressure dielectric barrier discharge (LPDBD) produced with Ar/O2 and Ar/Air technique causing biological stimulation leading to improved germination and growth in wheat. Both plasma treatments caused rougher and chapped seed surface along with noticeable improvement in seed germination in wheat. Beside this, seed H2O2 concentration significantly increased compared to controls subjected to Ar/O2 and Ar/Air while this phenomenon was more pronounced due to Ar/Air plasma. Analysis of plants grown from the plasma treated seeds showed significant improvement in shoot characteristics, iron concentration, total soluble protein and sugar concentration in comparison with the controls more efficiently due to Ar/O2 plasma than that of Ar/Air. Further, none of the plasma treatments caused membrane damage or cell death in root and shoot of wheat. Interestingly, Ar/O2 treated plants showed a significant increase (2-fold) of H2O2 compared to controls in both root and shoot, while Ar/Air plasma caused no changes in H2O2. This phenomenon was supported by the biochemical and molecular evidence of SOD, APX and CAT in wheat plants. Plants derived from Ar/O2 treated seeds demonstrated a significant increase in SOD activity and TaSOD expression in roots of wheat, while APX and CAT activities along with TaCAT and TaAPX expression showed no significant changes. In contrast, Ar/Air plasma caused a significant increase only in APX activity in the shoot. This suggests that Ar/O2 plasma caused a slight induction in H2O2 accumulation without triggering the H2O2 scavengers (APX and CAT) and thus, efficiency affect growth and development in wheat plants. Further, grafting of control and Ar/O2 treated plants showed a significant increase in shoot biomass and H2O2 concentration in grafts having Ar/O2 rootstock regardless of the type scion attached to it. It indicates that signal driving Ar/O2 plasma mediated growth improvement in wheat is possibly originated in roots. Taken together, this paper delivers new insight into the mechanistic basis for growth improvement by LPDBD technique.

PECULIARITIES OF VARIABILITY OF MORPHOLOGICAL FEATURES OF SATUREJA HORTENSIS L. IN NATURAL POPULATIONS OF DAGHESTAN

The structure of variability and intraspecific differentiation of Satureja hortensis L. (Lamiaceae) are studied on the basis of a complex of morphological features along a high-altitude gradient. Biomorphological peculiarities in four geographically remote locations are studied. The volume of each sample is 30 plants. The dimensional and quantitative features are taken into account. The dry mass of plants, foliage and reproductive effort are determined. A decrease in the dimensional and quantitative features of Satureja hortensis with a set of altitudes above sea level is noted. In the studied populations a high variability of the number of lateral branches per plant (CV = 21,626,0 %) is observed. With a set of heights, the percentage of foliage (28,535,2 %) and reproductive effort (6,611,0 %) is increase. As a result of the conducted studies, it was revealed that a significant contribution to variability of the Satureja hortensis features is made by a complex of abiotic and biotic factors caused by a high-altitude gradient. The correlation coefficient reflects the negative relationship of all the counted features with a high-altitude gradient, except on of the inflorescences mass. In the studied populations a high degree of variability on the weight characteristics of separate fractions and shoot as a whole is observed.

EFFECT OF SILICA ON PHYSIOLOGICAL AND ULTRASTRUCTURE CHARACTERS IN BARLEY (HORDEUM VULGARE L.) PLANT UNDER SALT STRESS

Salt stress is one of several major abiotic stresses that affect plant growth and development, and there are many evidences that silicon can ameliorate the injuries caused by high salinity. This study presents the results of an assay concerning: (1) the effect of NaCl induced salt stress in barely plant (cultivar Giza 123) and (2) the possible mitigating effect of silicon in saline conditions. In these study, different concentrations of NaCl (200 & 300 mM) used singly or in combination with silicon (0.5&1.0 mM potassium silicate). Morphological characters of shoot and roots, membrane stability index, relative water content, sodium, potassium, silica, photosynthetic pigments content and some antioxidant enzymes, as well as leaf electron microscope were evaluated. The results showed that, all parameters analyzed decreased except antioxidant enzymes and sodium content were drastically increased by increased salt levels. The supply of silicon (1mM) has successfully mitigated the effect of salinity at 300 mM NaCl. In conclusion, we affirmed that, salt stress is harmful for cape barley plants and the addition of silicon showed effective in mitigating the saline effects.

Release of carbon and nitrogen from fodder radish (Raphanus sativus) shoots and roots incubated in soils with different management history

ABSTRACTPlant roots are generally considered to decompose slower than shoots and contribute more to accumulation of soil organic matter, and management history is expected to shape the structure and function of decomposer communities in soil. Here we study the effect of chemical characteristics of shoots and roots from fodder radish (Raphanus sativus oleiformis L.), a widely used cover crop, on the release of their C and N after addition to soil. Shoots and roots were incubated for 180 d at 20°C using four soils with different management histories (organic versus mineral fertiliser, with and without use of cover crops), and the release of CO2 and extractable mineral N was determined. More shoot C than root C was mineralised during the first 10 d of incubation. After 180 d, 58% of the C input was mineralised with no difference between shoots and roots. At the end of incubation, shoots had released more N (42% of shoot N) than roots (28% of root N). Moreover, management history did not affect net mineralisation of added plant C. Residues incubated in soil with a management history involving cover crops showed an enhanced net N mineralisation. Therefore, long-term decomposition of C added in radish shoots and roots is unaffected by differences in chemical characteristics or soil management history. However, the net mineralisation of N in shoots is faster than for N in roots, and net N mineralisation of added materials is higher in soil with than without a history of cover crops.Abbreviations: CC: cover crop; IF: inorganic fertilizer; M: manure

ЗБЕРЕЖЕННЯ EX SITU КИЗИЛЬНИКІВ ФЛОРИ СИБІРУ У БОТАНІЧНОМУ САДУ ІМ. АКАД. О. В. ФОМІНА КИЇВСЬКОГО НАЦІОНАЛЬНОГО УНІВЕРСИТЕТУ ІМ. ТАРАСА ШЕВЧЕНКА

Відзначено, що колекція видів роду Cotoneaster Medik. у ботанічному саду ім. акад. О. В. Фоміна Київського національного університету ім. Тараса Шевченка – найбільша у Східній Європі, налічує 200 видів та культиварів, серед яких кілька представників флори Сибіру: С. сommixtus (C. K. Schneider) Flinck et Hylmo;; С. kyachticus, species nov.; C. laxiflorus Jacq. ex Lindl.; C. logginovii Grevtsova; C. lucidus Schlecht.; C. megalocarpus M. Popov.; C. mongolicus Pojark.; C. neo-popovii Czerepanov sp. nov.; C. tjulinae Pojark.; С. yacuticus J. Fryer et B. Hylmo. Зазначено, що C. kyachticus, sp. nov., який тривалий час у ботанічному саду культивовано під назвою C. melanocarpus Fisch.ex Blytt, після знайомства з гербарієм природних зборів Сибіру (м. Новосибірськ) виокремлено в інший таксон. Наведено детальний опис пагонів, листків, квіток, плодів та насіння інтродукованих кизильників сибірської флори, виділено діагностичні ознаки, що сприяють ідентифікації таксонів. Наголошено, що аналіз морфологічних ознак C. neo-popovii та C. tjulinae дає всі підстави відновити ці види у списках флори Сибіру, з яких упродовж останнього часу вони вилучені. Встановлено, що на цей час в Ботанічному саду ім. акад. О. В. Фоміна Київського національного університету ім. Тараса Шевченка зберігається ex situ дев'ять видів Cotoneaster флори Сибіру та три форми міжродового гібриду × Sorbocotoneaster pozdnjakovii Pojark.

Yanliaoa, an extinct genus of Cupressaceae s. l. from the Middle Jurassic, northeastern China

Yanliaoa is a common fossil in the Middle Jurassic of western Liaoning, eastern Inner Mongolia and northern Hebei Province, China. It is an important element of the Yanliao biota. The genus was established by Pan in 1977 for fossil plants from the Middle Jurassic Haifanggou Formation in Xiasanjiaochengzi, western Liaoning Province, and in present paper, the genus Yanliaoa is studied based on new material. Pan never designated a type specimen and his fossil material cannot be located. We designate a type specimen here for Yanliaoa, so that the genus name Yanliaoa remains valid. Yanliaoa sinensis Pan emend. Tan et al., is found in the same locality and formation as the lost specimens, Y. sinensis of Pan, 1977. Yanliaoa daohugouensis n. sp., a new species with epidermal anatomy, is from the Middle Jurassic Daohugou, Inner Mongolia. A holotype is also selected from the new material for this new species. Characters of the leafy shoots and ovulate cones of Yanliaoa are emended. The epidermal anatomy of this genus is described for the first time. Compared with other extant and extinct species of Cupressaceae s. l., the current species can be distinguished from any known species both by the leafy shoot characters and its epidermal anatomy. It further indicates that Yanliaoa is an extinct and endemic conifer found in the Middle Jurassic of northeastern China.

Morphological, Physiological and Nutritional Effects of Irrigation Frequency on Macaúba Palm Seedlings

The commercial nurseries of macaúba palm (Acrocomia aculeata) have experienced excessive seedling mortality, which is possibly due to the lack of information about the proper growing practices. The goal of this study was to investigate the response of macaúba seedlings to water stress using different irrigation frequencies during the early seedling stage. The experiment was carried out in a macaúba palm nursery located in João Pinheiro, Minas Gerais, Brazil. The treatments started 30 days after sowing. At 90 days after sowing, the morphological (number of leaves, stem diameter, shoot length, root weight and the fresh and dry matter content of leaves, stem and roots), physiological (allocation of photosynthates) and chemical (nutrient content in the shoot) characteristics were evaluated. The results indicated that shoot height and stem diameter became smaller as the frequency of irrigation was reduced. However, the accumulation of fresh biomass in leaves and stems, and the leaf and root dry biomass became higher under the same condition. When water stress was induced in younger seedlings, the allocation of photosynthates occured more proportionally across all organs of the plants. The highest accumulation of K, S and Fe in the shoot were observed in plants that were exposed to water stress. N accumulation was higher in the aerial part of the seedlings as the irrigation frequency increased. However, the opposite behavior was observed for P, which accumulation was lowest in the control treatments.

Identification of Discriminating Morphological Descriptors for Characterization of Seabuckthorn (Hippophae rhamnoides L.) Germplasm in Himachal Pradesh

Identification of discriminating morphological descriptors for characterization of Seabuckthorn (Hippophae rhamnoides L.) germplasm in Himachal Pradesh was undertaken in ten different major gene pool areas of Seabuckthorn in Spiti Valley, where 80 per cent population is of Hippophae rhamnoides L. Twenty plants of each gene pool area were selected during the end of growing season. Plant shoot, leaf blade, pubescence and fruit characteristics were recorded. Twenty two morphological traits were recorded for vegetative and reproductive descriptors, which is comprised of Qualitative and Quantitative characteristics. Study concluded with preparation of DUS (Distinctiveness, Uniformity and Stability) guidelines for developing a new species/sub species or variety or new clone which will help in further breeding and genetic improvement programme. The present study identifies the morphological descriptors that are most relevant for characterization of Seabuckthorn (Hippophae rhamnoides L.) in cold desert eco-system of Himachal Pradesh.

EFFECT OF GROWTH REGULATORS ON ROOTING OF CUTTINGS IN PLUM CV. KALA AMRITSARI

1200 cuttings made from the trees of Plum cv. Kala Amritsari were planted in 60 beds of size 1×1m., with 20 cuttings on each bed. Uniform sized 40 cuttings per replication were treated with ten treatments of IBA and PHB growth regulators by slow dip (24 hours) and quick dip (2 minutes) method before planting along with control. Results showed that IBA@2000ppm quick dip was found to be significant in improving the shoot and root characters in cuttings with maximum shoot length (16.87cm), average shoot girth (0.46cm), shoot number (4.22), fresh weight of shoots (6.82), dry weight of shoots (1.43g), leaf number (154.28), average leaf area (305.79 cm2), root number (44.90), average root length (10.88cm), length of longest root (13.5cm), fresh weight of roots (1.52g), dry weight of roots (1.09). While the cuttings treated with slow dip of IBA 150 ppm exhibited significant survival percentage (81.00%), percentage of rooted cuttings (74.33%) and sprouting percent (75.17%).

Mechanical properties of cotton shoots for topping

Cutting the shoots of cotton plants (topping) at about 10–20 cm from the top of plants is a cultural practice, which may offer advantages to improve yield and yield components in cotton production. The cutting forces of plant stalks were reported in the literature, which help understand the mechanical properties of stalks for a cultivar of field crops. However, the shearing characteristics of cotton shoots have not been addressed yet. The objective of this study was to determine some physical and mechanical properties of cotton (Gossypium hirsutum L.) shoots. The test specimens were obtained from two different plant segments, i.e. 0–15 cm (Segment A) and 16–30 cm (Segment B) from the top of cotton plants, in 21 plots in an ongoing cotton topping study. The samples were collected from each plot and were subjected to shearing test using a universal test machine in the laboratory. In Segment A, average shoot diameter, shearing force, water content, maximum shearing stress, and specific shearing energy were determined to be 4.35 mm, 73 N, 72%, 4.94 MPa, and 0.069 J mm−2, respectively. In Segment B the same parameters were 5.79 mm, 121 N, 64.8%, 4.65 MPa, and 0.078 J mm−2, respectively. The difference between the Segment A and B was significant at 5% level for shearing stress while all others parameters showed differences at 1% level. Although displacement at the bioyield point was similar in both sampling locations, the maximum shearing force requirement was more (121 N) in Segment B compared with Segment A (73 N) suggesting that topping should be done as high as possible from the ground to complete the topping process with low energy consumption. In terms of cutting energy requirement, it was concluded that the topping should be done as early as possible from 100 to 120 days from the planting.

Early drought effect on canopy development and tuber growth of potato cultivars with different maturities

The morphological growth characteristics of shoots, stolons, and tubers were measured on potatoes (Solanum tuberosum L.) grown in irrigation and drought from plant emergence. Three cultivars with a wide range of seasonal maturing patterns, Chubaek (very early), Superior (medium-early), and Jayoung (late), were used. The drought was maintained up to the tuberization stage in the year 2015, and it was extended to early tuber bulking in the year 2016. The drought delayed the time to full canopy development by 2–6days and decreased the growths of shoots in terms of stem length, stem thickness, number of stems, and fresh weight of the shoots. The harvest index was increased in all cultivars due to the decreased shoot growth. The early drought also increased the length of underground stolons. However, the decreases in stem thickness and stem number and the increases in harvest index and stolon length were only significant in the year 2016. Even though the drought did not affect tuberization in early and medium-early cultivars, it decreased early tuber growth by suppressing the longitudinal growth expressed by the ratio of length to width of the tubers. The decrease of tuber growth was observed until the end of the season with the exception of Superior in 2016. In late maturing cultivar, tuber initiation and tuber yield were dependent on the season or length (severity) of the drought. In 2016 when late cultivar, Jayoung, experienced a long drought starting from the emergence of the plants to early tuber bulking, the drought induced earlier tuberization than irrigation treatment, and showed a higher harvest index than in 2015. The early tuberization and tuber bulking due to the long drought induced increased tuber yields. The occurrence of second growth tubers was highly attributed to the maturity of cultivars in both years and the drought in 2016.