Tuber Dry Weight Research Articles

Characterization of Starch from Tubers of Yam Bean (Pachyrhizus ahipa)

Detailed studies of the starch present in tubers of six accessions of Pachyrhizus ahipa (ahipa) have been carried out using starches from tubers of P. erosus (Mexican yam bean) and seeds of ahipa and wheat for comparison. Starch accounted for 56-58% of the tuber dry weight with granules occurring in a range of geometric forms and in sizes from below 5 microm to about 35 microm (mean about 10 microm in all accessions except two). The amylose content ranged from 11.6 to 16.8% compared with 16.9% in P. erosus tubers and over 23% in the seed starches. X- ray diffraction analysis showed A-type or C(A)-type diffraction patterns. The chain-length distribution of the amylopectin after enzyme debranching showed a peak at DP11 similar to that of wheat starch, but had a less marked shoulder at DP 21-22 and contained a higher proportion of longer chains. Differential scanning calorimitry showed an endothermic peak corresponding to gelatinization with T(max) ranging from 59 to 63 degrees C, which was similar to the T(max) of wheat (about 64 degrees C). The composition of the ahipa starch may mean that it is suitable for food applications that require low amylose content and low retrogradation after processing.

Effect of sources and levels of nutrients on growth and yield behaviour of pop corn (Zea mays) and potato (Solanum tuberosum) sequence

A field experiment was conducted during 200809 and 200910 at New Delhi, to study the effect of organic sources of nutrients on growth, yield and yield attributes of pop porn (Z ea mays averta Sturt)-potato ( Solanum tuberosum L.) cropping system. The experiment consisted of 24 treatment combinations with 8 treatments in pop corn [control, recommended dose of fertilizers (RDF) (N P K kg/ha), farmyard manure equivalent to120 kg N/ 120 25 35 ha (FYM ), leaf compost equivalent to 120 kg N/ha (LC ), vermicompost equivalent to 120 kg N/ha (VC ), 120 120 120 farmyard manure equivalent to 90 kg N/ha (FYM ), leaf compost equivalent to 90 kg N/ha (LC ) and 90 90 vermicompost equivalent to 90 kg N/ha (VC )] and 3 treatments in potato crop [control, farmyard manure equiva- 90 lent to 60 kg N/ha (FYM ) and farmyard manure equivalent to 90 kg N/ha (FYM )]. The application of RDF 60 90 (N P K kg/ha) recorded significantly highest plant height, leaf-area index and dry matter with higher values of 120 25 35 yield attributes, viz. cob length and girth, cobs/ha over the control. Application of vermicompost equivalent to 120 kg N/ha was the best source and remained at par with VC , FYM , FYM and N P K kg/ha for growth and 90 120 90 120 25 35 yield attributes of pop corn. Similar trend in respect of grain and stover yield was also found. Due to residual fertil- ity of FYM (equivalent to 120 kg N/ha) potato recorded the highest plant height, LAI, number of haulms and dy matter in haulms. Both FYM (equivalent to 90 kg/ha) and vermicompost (equivalent to 120 kg N/ha) exhibited the effects similar to FYM @ 120 kg N/ha. The yield and yield attributes of potato, viz. tubers/hill, fresh and dry weight of tubers, tuber yield and haulm yield also exhibited similar trend. Regarding direct effects of FYM, application of FYM equivalent to 90 kg N/ha in potato recorded the higher plant height, LAI, haulms/hill, dry matter in haulms; and yield and yield attributes compared to FYM equivalent 60 kg N/ha and control.

Productivity and profitability of different cultivars of potato (Solanum tuberosum) as affected by organic and inorganic sources of nutrients

Field experiments were conducted during winter of 2005-06 and 2006-07 at Hooghly, West Bengal to investi- gate the effect of different organic and inorganic sources of nutrients on productivity and profitability of potato ( Solanum tuberosum L.) cultivars. The treatments consisted 3 varieties, viz. Kufri Chipsona-1, Kufri Chipsona-2 and Kufri Jyoti in main-plots and 4 nutrient sources, viz. Farmyard manure (FYM) @ 35 t/ha (N ), FYM @ 30 t/ha 1 + biofertilizers (N ), FYM @ 25 t/ha + mustard cake @ 1 t/ha (N ), recommended dose of NPK i.e. 180:66:125 kg/ 2 3 ha N, P, K (N ) in sub-plots. Varieties had significant variations in growth and yield attributes, yield and nutrient up- 4 take. Higher growth attributes were recorded under Kufri Chipsona-1 except plant height. Hence, Kufri Chipsona- 1 gave maximum number of tubers, total tuber yield (28.18 and 28.39 t/ha), NPK uptake, net profit and B:C ratio (1.28, 1.22). Among sources of nutrient recommended dose of NPK showed better performance in all respects and registered 4.7 to 9.7% more tuber yield when compared with other nutrient sources. The highest B:C ratio (1.34, 1.29) was also recorded in recommended dose of NPK treatment. Higher dry weight of tubers (718.15, 722.40 g/m2), number of tubers (680.21, 690.74 thousand/ha) and tuber yield (29.44, 29.89 t/ha) were obtained from Kufri Chipsona-1 potato treated with recommended dose of NPK.

Influence of Norflurazon Placement on Yellow Nutsedge (Cyperus esculentus)1

Abstract: Greenhouse studies were conducted to determine yellow nutsedge response to selective placement of a 5-cm layer of norflurazon-treated soil above, below, or above plus below pregerminated nutsedge tubers. Norflurazon at 1.68 kg ai/ha applied postemergence (POST) as a foliar, soil, or foliar plus soil treatment was also evaluated. Soil concentrations of norflurazon at 1.5 mg/kg (w/w) applied below or above plus below nutsedge tubers reduced yellow nutsedge shoot numbers at least 69%, shoot height at least 71%, shoot dry weights at least 77%, and root tuber dry weights at least 89%. Yellow nutsedge growth reduction with norflurazon was greatest when norflurazon was placed in the soil profile below or above plus below the yellow nutsedge tubers. Placement of norflurazon above yellow nutsedge tubers did not reduce shoot number, height, or dry weight until the foliar portion of plants were removed 39 d after treatment. POST application of norflurazon did not reduce initial yellow nutsedge shoot number...

Development of micropropagated potato plants over three phases of growth as affected by temperature in different phases

To assess (after)effects of temperature on plant development, in vitro potato plantlets produced at 17 or 23 °C (normalisation phase, 3 weeks) were planted into soil in growth chambers at 18/12 or 26/20°C (transplant production phase, 2 weeks), and transplanted to glasshouses at 18/12 or 26/20°C (tuber production phase, 6 weeks). The latter phase commonly takes place in the field. Transition from one phase to another, especially from in vitro to in vivo conditions, greatly increased leaf growth and to a smaller extent stem growth. Within a phase, higher temperature stimulated vegetative growth, but delayed tuber formation and reduced tuber yields, harvest index (HI) and tuber dry matter concentration. Temperature during tuber production was more important for high yield than temperatures during earlier phases. Normalisation and transplant production temperatures nevertheless showed after-effects in later phases. Lower normalisation temperatures advanced plant development: they increased vegetative growth in subsequent phases and finally increased fresh tuber yield and HI. This could have yield advantages at locations where field production seasons are short. Lower transplant production temperatures reduced vegetative growth in the next phase, but enhanced early tuber production. Finally they increased tuber dry weight and HI when tuber production temperatures were high. This may increase yield at locations where field conditions delay tuber formation.

Effects of moderate drought conditions on green leaf number, stem height, leaf length and tuber yield of potato cultivars

Our objective was to define sensitive morphological indicators that could be used to discriminate between drought sensitive and drought tolerant potato cultivars before final tuber yield is reached. A total of six potato cultivars contrasting for drought tolerance and earliness were subjected to three levels of water supply in two field trials in 1995 and 1996. We examined which parameter among stem height, number of green leaves and leaf length (the two latter parameters were only measured on two cultivars) was most sensitive to moderate drought conditions and responded similarly to water shortage regarding tuber yield, tuber number and average tuber dry weight. Drought reduced the number of green leaves in cultivars Krostar and Désirée, respectively, up to 22 and 25% 124 days after planting during the season but this effect levelled off towards the end of the season. Drought also induced significant length reductions (29, 43 and 53%, respectively, for the leaf numbers 17, 18 and 19) but there were no differences among the two cultivars examined. Stem height was sensitive to drought and the effect was stronger on later cultivars especially when water shortage started early as in 1996. In 1996, stem height ratios were negatively related ( R 2=0.80) to TDWS (tuber yield ratio indicative of drought tolerance) whereas they were positively related in 1995 ( R 2=0.21). However, care is needed as the negative relationship of 1996 was associated to earliness of cultivars. Indeed, stem height was less reduced in early cultivars (13 and 14% for Eersteling and Jaerla, respectively) than in mid-late cultivars (25 and 29% for Désirée and Nicola, respectively). In the drought treatment, no supernumerary tuber was observed across the season contrary to the irrigated treatment. According to the year, final tuber number or average tuber dry weight was reduced by the drought treatment. Reduction in tuber number (17%) in the drought treatment was not associated to lower tuber yields due to compensation by average tuber dry weight (6%). Different growth strategies can be followed by the potato plant to adapt to different drought conditions without tuber yield being significantly affected.

Antagonistic Effect of Thiazopyr on Azafenidin to Control Yellow Nutsedge (Cyperus esculentus)1

Greenhouse experiments evaluated azafenidin and thiazopyr applied separately, as a tank mix, or in rapid succession, for preemergence control of yellow nutsedge (Cyperus esculentus) and hairy beggarticks (Bidens pilosa). Average of yellow nutsedge shoot dry weights at 21 and 42 d after treatment (DAT), indicated that azafenidin at 0.28, 0.56, and 1.12 kg ai/ha controlled 70, 86, and 90%, respectively, and thiazopyr at 1.12 kg/ha controlled 10% of yellow nutsedge. However, when thiazopyr at 1.12 kg/ha was tank-mixed with azafenidin at 0.28, 0.56, and 1.12 kg/ha, yellow nutsedge control averaged for 21 and 42 DAT was reduced to 41, 69, and 78%, respectively. Root plus tuber dry weight of yellow nutsedge increased threefold when 1.12 kg/ha thiazopyr was mixed with 0.28 kg/ha azafenidin, compared to azafenidin applied alone at the above rate. When the herbicides were applied sequentially, within minutes of each other, the antagonistic responses were reproduced, independent of the order of herbicide application. Thiazopyr applied at 0.56 and 1.12 kg/ha stimulated the emergence and establishment of hairy beggarticks and antagonized azafenidin for the control of yellow nutsedge based on a mathematical model. Although thiazopyr reduced the preemergence herbicidal efficacy of azafenidin on hairy beggarticks control, antagonism could not be determined because of the stimulatory effects of thiazopyr on hairy beggarticks emergence.Nomenclature: Azafenidin; thiazopyr; hairy beggarticks, Bidens pilosa L. #3 BIDPI; yellow nutsedge, Cyperus esculentus L. # CYPES.Additional index words: Herbicide interaction, stimulation, scarification, antagonism, spanish needles, Bidens alba, Bidens leucantha.Abbreviations: DAT, days after treatment; PRE, preemergence; WAT, weeks after treatment.

Responses of early and late potato cultivars to moderate drought conditions: agronomic parameters and carbon isotope discrimination

Our main objective was to test under moderate drought conditions the hypothesis that early cultivars behave better than late cultivars under conditions of drought occurring late in the season whereas late cultivars would be less susceptible to a drought occurring early in the season. Agronomic parameters [tuber dry weight, harvest index, dry matter content, tolerance to a decrease in water supply (TDWS) and carbon isotope discrimination ( Δ)] were measured in six potato genotypes ( Solanum tuberosum L.) subjected in two field trials (1995 and 1996) to three levels of water supply (treatments: 1, rainfall+irrigation; 2, rainfall only; 3, rainfall reduced to stemflow during early growth). In both years, treatment 3 (lower water supply) reduced significantly tuber dry yield and harvest index in comparison with treatment 1 (higher water supply). Tuber dry matter content was increased significantly only by treatment 3 in 1996. For these parameters cultivars did not differ in their response to the lower water regimes except in the case of tuber dry matter content during one year (1996). TDWS defined as tuber dry weight of treated plots relative to the tuber dry weight of treatment 1 allowed more discrimination among the behaviour of cultivars in case of moderate drought than yield and Δ. Our TDWS results confirm partly the hypothesis tested: in 1996, TDWS values of mid–late cultivars were higher than those of early cultivars in the case of early drought (treatment 3), indicating that later cultivars support better a drought stress in the early part of the season. Differences among cultivars in the responses of Δ to the different water regimes could not be shown, and there was no difference between the values of Δ observed for early and late cultivars. In our moderate drought conditions an escape mechanism of earlier cultivars could not be confirmed through the consideration of the Δ values observed. The linear regression of Δ on TDWS gave a positive slope significantly different from zero ( n=24) but the R 2 values were low ( R 2=0.41).

Plastic and non-plastic variation in growth of newly established clones of Scirpus (Bolboschoenus) maritimus L. grown at different water depths

The importance of plastic responses to water depth as compared to non-plastic (developmental) changes in ramet (consisting of a culm e.g., stem with leaves, rhizome spacers and – tuber, and roots) characteristics of newly established clones of the emergent macrophyte Scirpus maritimus L. was examined. Clones were established from seeds and grown in outdoor ponds at water depths of 0 (waterlogged), 10, 20, and 30 cm. Number and dry weight of ramets were higher at 0 and 10 than at 20 and 30 cm water depth. There was no plastic but a high non-plastic variation in rhizome spacer lengths. In response to water depth culms were longer, but the relative length growth rate of culms and leaf morphology remained unaffected by water depth. Total ramet dry weight did not differ between water depths, but with increasing water depth the proportional allocation of dry matter to stems increased at the expense of roots and rhizome spacers. In sequentially produced ramets dry weight increased, and the proportional dry matter investment in tubers (storage organs) and roots increased at the expense of leaves and rhizome spacers. Plasticity in morphology and biomass allocation of ramets was directed towards a fast emergence from the water. However, no plasticity in ramet and tuber dry weight was apparent. Therefore, the non-plastic rather than the plastic variation in ramet characteristics is of great importance for the persistence of newly established S. maritimus clones after drawdowns.

Dry Matter Allocation and Loss in Jerusalem Artichoke (Helanthus tuberosus, L.) during Growth and Field Storage

Jerusalem artichokes are one of a small number of crops that store carbon predominately in the form of inulin, a straight chain fructosan. There has been a tremendous increase in interest in inulin due to its dietary health benefits for humans and calorie replacement potential in processed foods. We measured the allocation of dry matter within the crop (cv. Sunckoke) during an entire growth cycle by harvesting plants over a 40-week period (2-week intervals) from initial planting through field storage. Plant characters assessed were: no. of basal stems, leaves, branches, flowers, and tubers; the dry weight of leaves, branches, flowers, tubers, and fibrous roots; and date of flowering. Total dry weight of above-ground plant parts increased until 18 weeks after planting (22 Aug.) and then progressively decreased thereafter. Tuber dry weight began to increase rapidly ≈4 weeks (19 Sept.) after the peak in above-ground dry weight, suggesting that dry matter within the aerial portion of the plant was being recycled into the storage organs. Tuber dry weight continued to increase during the latter part of the growing season, even after the first frost. Final tuber yield was 13.6 MT of dry matter/ha.

Effects of shading on the growth of nutsedges (Cyperus spp.)

Greenhouse studies were carried out to determine the effects of different shading levels on biomass accumulation of purple and yellow nutsedge. Artificial shading levels provided were 20, 40, 60, and 80% of incident sunlight in addition to the full sunlight control (0% shading). Yellow nutsedge shoot and tuber number, plant height, and shoot and tuber dry weight were less affected by 20% shading than were these variables for purple nutsedge. Shoot and tuber dry biomass for both species responded linearly to shading level. In yellow nutsedge, 80% shading reduced dry matter partitioning to the tubers and increased partitioning into the shoots. In contrast, biomass partitioning to purple nutsedge tubers was decreased under high shade conditions without increases in partitioning to the shoots. The light compensation point was lower for yellow nutsedge than for purple nutsedge. This could possibly explain the wide distribution of yellow nutsedge in relatively low light intensity environments, in contrast with purple nutsedge, which generally occurs in tropical areas where higher light intensities are the norm.

Quantifying Total, N, and Non-N Related Crop Rotation Effects Without 15N

ABSTRACT The N benefits attributed to legumes in crop rotations are often overestimated because the technique for quantifying this benefit without 15N includes rotation effects not directly related to N. This study was conducted to test an approach proposed in the literature for delineating such effects without requiring the use of 15N. Potato (Solanum tuberosum L. cv. Norwis) was grown continuously and in two-year rotations with alfalfa (Medicago sativa L. cv. Nitro), hairy vetch (Vicia villosa Roth), or white lupin (Lupinus albus L. cv. Ultra). Potato was fertilized with 0, 90, or 180 kg N ha−1 as (NH4)2S04. The total, N, and non-N effects of crop rotation were calculated based on tuber dry weight and plant N uptake for the rotation systems and the tuber dry weight vs. plant N uptake relationship for continuous potato. The total effect of crop rotation generally declined upon increasing N fertilizer from 0 to 90 kg N ha−1, apparently due to decreasing importance of the N effect with added fertilizer. Non-N related effects mostly remained static across fertilization regimes. Those effects attributed to N generally declined upon adding 90 kg N ha−1 in a relatively dry year; and upon adding 90 and 180 kg N ha−1 in a year with more favorable precipitation. Calculated N effects with no N fertilizer reflected the quantity and quality of legume crop residues. This method does allow assessment of total, N, and non-N related rotation effects. However, the approach appears sensitive to climatic conditions, and data should only be subjected to analysis where a yield response to N exists.

Influence of native endomycorrhiza, soil flooding and nurse plant on mycorrhizal status and growth of purple nutsedge ( Cyperus rotundus L.)

A study was made to investigate the effects of native endomycorrhizal fungi, soil flooding and nurse plant (onion) on the mycorrhizal status, growth and phosphorus (P) uptake of purple nutsedge ( Cyperus rotundus L.). Above ground (AG) and below ground (BG) dry weight of mycorrhizal purple nutsedge plants were significantly lower than the non-mycorrhizal plants, but ratios of BG:AG dry weight were the same except when grown with onion. Mycorrhizal infection was characterized by vesicles and hyphae, both intraradical and extramatrical, but lacked arbuscules. Percentage root colonization of purple nutsedge and onion was significantly higher when the two grew together, but plants growing alone had less infection. Flooding of soil inhibited mycorrhizal formation in purple nutsedge, and mycorrhizal infected plants produced smaller tubers than uninfected plants. AG tissue P concentration was lower in mycorrhizal purple nutsedge but BG P concentration had no significant variations between infected and uninfected plants. P utilization efficiency (PUE) was similar for mycorrhizal and non-mycorrhizal purple nutsedge. Plants in flooded soil had the maximum AG and BG dry weights, tuber dry weight and P content, but had lower AG:BG dry weight ratio and PUE.

Synthesis of fructans in tubers of transgenic starch-deficient potato plants does not result in an increased allocation of carbohydrates.

Inhibition of starch biosynthesis in transgenic potato (Solanum tuberosum L. cv. Désirée) plants (by virtue of antisense inhibition of ADP-glucose pyrophosphorylase) has recently been reported to influence tuber formation and drastically reduce dry matter content of tubers, indicating a reduction in sink strength (Müller-Röber et al. 1992, EMBO J 11: 1229-1238). Transgenic tubers produced low levels of starch, but instead accumulated high levels of soluble sugars. We wanted to know whether these changes in tuber development/sink strength could be reversed by the production of a new high-molecular-weight polymer, i.e. fructan, that incorporates sucrose and thereby should reduce the level of osmotically active compounds. To this end the enzyme levan sucrase from the gram-negative bacterium Erwinia amylovora was expressed in tubers of transgenic potato plants inhibited for starch biosynthesis. Levan sucrase was targeted to different subcellular compartments (apoplasm, vacuole and cytosol). Only in the case of apoplastic and vacuolar targeting was significant accumulation of fructan observed, leading to fructan representing between 12% and 19% of the tuber dry weight. Gel filtration and 13C-nuclear magnetic resonance spectroscopy showed that the molecular weight and structure of the fructan produced in transgenic plants is identical to levan isolated from E. amylovora. Whereas apoplastic expression of levansucrase had deleterious effects on tuber development, tubers containing the levansucrase in the vacuole did not differ in phenotype from tubers of the starch-deficient plants used as starting material for transformation with the levansucrase. When tuber yield was analysed, no increase but rather a further decrease relative to ADP-glucose pyro-phosphorylase antisense plants was observed.

Crop rotation and N fertilization effects on growth, yield, and disease incidence in potato

Crop rotation can be an effective mechanism for reducing disease incidence and contributing nitrogen (N) to succeeding crops. Interactions of plant pathogen suppression and soil nutrient availability may also exist, adding to the cropping system complexity. This study examined the impact of crop rotation, N fertilization, and their interaction on growth, yield, andRhizoctonia solani incidence in potato (Solanum tuberosum L. Norwis). Potato was grown continuously and in two-year rotations with annual alfalfa (Medicago sativa L. Nitro), hairy vetch (Vicia villosa Roth), white lupin (Lupinus albus L. Ultra), and oat (Avena sativa Astro). Fertilizer was banded at potato planting with 0, 45, 90, 135, 180, or 225 kg N ha−1 as (NH4)2SO4. Approximately 58% of continuous potato possessed stem lesions caused byR. solani, but only 12 to 22% of potato stems from other rotations possessed lesions. Tuber dry weight was affected by crop rotation in 1989, a dry year, but not in 1990. Apparent N fertilizer replacement values for hairy vetch, Nitro alfalfa, white lupin, and oat were 65, 43, 26, and 11 kg N ha−1, respectively. All crop rotations studied appeared to enhance potato production by reducing stem infection byR. solani. Vetch and alfalfa provide additional benefits through their N contributions.

Potato growth in a porous tube water and nutrient delivery system

Potato ( Solanum tuberosum L.) cv. ‘Norland’, vegetative growth and tuber productivity grown in the porous water and nutrient delivery system (PTNDS) developed by the Wisconsin Center for Space Automation and Robotics were compared with the vegetative growth and tuber productivity of plants grown in a peat: vermiculite potting mixture (PT/VR). The plants were grown at 12, 16, and 24-h light periods, 18°C constant temperature, 70 % relative humidity, and 300 μmol·m −2·s −1 photosynthetic photon flux. Canopy height of plants grown in the PT/VR system was taller than that of plants grown in the PTNDS system. Canopy height differences were greatest when the plants were grown under a 24-h photoperiod. Leaf and stem dry masses were similar for plants grown in the two systems under the 12-h photoperiod. Under the 24-h photoperiod, leaf and stem dry masses of plants grown in the PT/VR system were more than 3 times those of plants grown in the PTDNS system. Tuber dry masses were similar for plants grown in the two systems under the 12-h photoperiod. Under the 24h-photoperiod, tuber dry weights of plants grown in the PT/VR system were more than twice those of plants grown in the PTDNS system. A slightly higher harvest index (ratio of tuber weight to leaf plus stem weight) was noted for the plants grown in the PTNDS than for the plants grown in the PT/VR system. Plants grown in the PTNDS system at the 24-h photoperiod matured earlier than plants grown at this photoperiod in the PT/VR system. Vegetative growth and tuber productivity of plants grown under the 16-h photoperiod generally were intermediate to those noted for plants grown under the 12 and 24-h photoperiods. These results indicate that potato plants grown in a PTNDS system may require less plant growing volume, mature in a shorter time, and likely produce more tubers per unit area compared with plants grown in the PT/VR system. These plant characteristics are a distinct advantage for a plant growing unit of a CELSS.

Influence of irrigation regimes on growth and yield of potato cv. Spunta

The effect of furrow and drip irrigation giving 0, 33, 66, 100 and 133% of the maximum evapotranspiration (ETM) was studied on leaf transpiration, stomatal resistance, tuber growth, yield and yield response of cv. Spunta. The research was carried out in Sicily in 1988 and 1989 on early potato crops grown during the winter/spring cycle. Increased water supply increased leaf transpiration, plant fresh weight, tuber growth rate, yield and earliness, and decreased stomatal resistance and tuber dry weight. A higher yield response was obtained at the lower water regimes (ETM of 33 and 66%). There were no significant differences between the two methods of irrigation.

Assimilate partitioning in Pachyrhizus erosus tubers under short days

The distribution of 14C products in yam bean (Pachyrhizus erosus) plants was measured as a function of time after a 14CO2 pulse‐chase experiment under short‐day conditions. The 14C declined by more than 70% in leaves during the first two hours, indicating that they actively exported carbon. Tubers were strong storage sinks for carbon and accumulated more than 80% of the total incorporated 14C after a 72‐h chase. The data show that, although sucrose represented about 21% of the tuber non‐structural carbohydate, i.e. 15% of the tuber dry weight, 14C did not accumulate in sucrose but in glucose, fructose and starch. The data indicate the existence of a separate sucrose pool which is affected only very slowly by recent assimilates. As a result, recent photosynthates, temporarily stored, may contribute to the reservoir of carbon available for nitrogen fixation. The data also suggest the existence of two distinct pools of amino acids in the tuber, one utilized mostly for protein synthesis and the other probably stored in the vacuole.

Model calculations for the effects of nitrogen, phosphorus, and potassium nutrition on the behaviour of potato tubers in storage

Empirical mathematical models are described for calculating the effects of varying supplies of nitrogen, phosphorus and potassium on pot and field grown tubers. Through optimization and simulation, potato tuber fresh and dry weight losses and chemical composition changes (ascorbic acid, citric acid, glucose, fructose, sucrose, nitrate) are calculated over a 6-month period of storage at 4°C. The effects of variation in single nutrients as well as of increasing N fertilization on storage are calculated. Calculations giving the maximum vitamin C content at harvest and after storage indicate the nutrient supply required.

Effects of Scion and Stock on Root Growth of Grafting Plants between Two Potato Varieties with Different Root Mass.

The relationships of root growth with shoot and tuber growths have still not been clear in potato plants. The aim of this report is to clarify whether a varietal difference in root growth of potato plants is determined by some inherent characteristics in the root organ per se, or affected by the growth of other organs. Four combinations of grafting plants between two late varieties, Norin 1 and Konafubuki, with different root mass were produced and cultured in large pot; (25 cm in diameter, 50 cm in depth) with plentiful water supply. Dry weight (DW) of each organ and leaf area were measured at three stages, just after the transplanting, approximately after the initial flowering and after the last flowering, for three years. Analyses of variance for the characters were performed using the years as replications. The stock genotypes significantly influenced root DW of the grafting plants at the three stages examined. The effects of scion genotypes on root DW were not significant. The negative relationship was found between root DW and tuber DW in the grafting plants. Shoot DW and leaf area were not significantly different among the grafting plants. We concluded that the difference in root DW between the two varieties was mainly due to the inherent characteristic in the dry matter partition to roots and tubers just after the tuber initiation.