Growth In Potatoes Research Articles

Paclobutrazol and benzylaminopurine improve potato yield grown under high temperatures in lowland and medium land

Abstract Potato is one of the most important vegetable crops in the world. In a tropical country such as Indonesia, potato is cultivated in highland that has low temperature. However, the extensification and intensification of potato cultivation cause environmental problems in the highland. Soil erosion is one of the common problems resulting from potato cultivation that applies heavy tillage. To prevent environmental problems, the land expansion for potato cultivation is carried out in both the medium and lowland. High temperature in both medium and lowland results in the limitation of plant growth and yield. Therefore, the present study aimed to evaluate the effect of plant growth regulators (PGRs), namely paclobutrazol and benzylaminopurine (BAP) application on the growth and yield of potatoes grown under high temperature in both lowland and medium land. A split-plot design was used in this experiment with the main plot as growing altitude, i.e., low and medium land, and the PGR treatments as the subplot, i.e., control, paclobutrazol at 100 mg L−1, BAP at 50 mg L−1, and a combination of paclobutrazol at 100 mg L−1 and BAP at 100 mg L−1. The result showed a reduction in plant growth and yield in potatoes grown in lowland compared to those in medium land. The application of paclobutrazol and BAP improved the number, the weight of tuber, and its starch content. The result indicated that the application of paclobutrazol and BAP could be used to solve an environmental limitation for potato cultivation in both lowland and medium land.

In vitro antimicrobial activity of „Carum carvi“ L. seed essential oil against pink potato spoilage flora

The objective of this research is to assess the ability of using Carum carvi L. seeds essential oil as a biological substance for controlling spoilage germs growth in potatoes during storage. The chemical composition of caraway seeds essential oil, analyzed by GC-MS and by gas chromatography with flame ionization detector (GC-FID), led to the identification of twelve compounds, where carvone was the main one with a percentage of 75.64 % of the total oil. The comparison of the microbial profiles of different potatoes samples showed the presence of the genus Citrobacter and three distinct fungi genera: Aspergillus, Phytophthora and Fusarium only for contaminated potato tubers with internal pink pigmentation. Thus, the antimicrobial activity of caraway seeds essential oil was studied against these strains. The antimicrobial activity of the oil against the isolated strains was evaluated through the agar diffusion method using different volumes (10, 20, 50 and 100 µl). All tested strains were inhibited by caraway seeds essential oil in a dose-dependent manner. The obtained results suggest the use of Carum carvi L. as a promising natural substance for the preservation of potatoes by contact vapor method.

Could chips and nuts be vector of food-borne outbreaks during happy hour?

Abstract Background A Greater tendency to eat meals outside the home has led to an increase in the attendance of restaurants, cafes, and fast food. That is one of the reasons why the global interest in handling food has risen over the years. The aim of this study is to understand the level of microbial contamination in the food that is served along happy hour in cafe. Methods This cross sectional pilot study was performed from April to May 2018 in the city of Siena, central Italy (<60000 citizens). Ten cafes were randomly selected. Samples of peanuts and potatoes were obtained in three different moments, at the beginning (T0), in the middle (T1), at the end (T2) of happy hours events. Collection of the samples was obtained using sterile kit and laboratory analysis was conducted in the University lab. The samples were located on selective medium and the growth of microbial pathogens were checked at 24 and 48 hours. The tested microorganisms were Enterococci, Staphylococci, Coliforms bacteria, Molds, and Yeasts. The statistical analyses were conducted using the Wilcoxon test using Stata 12. Results A significant Yeasts contamination appeared only on chips at T0, while within T0 and T1 we found a significant increase of Enterococci, Staphylococci, and Yeasts (p < 0.05) both in peanuts and chips. Comparing T1 and T2 only Yeasts showed significant growth in potatoes (p = 0.04). Between T0 and T2 we also found the growth of Coliforms bacteria in peanuts (p = 0.03). Conclusions We showed an increase in the microbial load associated with food handling, mostly of Enterococci. Long exposure time increased the likelihood of contamination and the possibility to exceed the dose for the occurrence of good outbreak. It is likely that offering small portions of handling food would reduce the manipulation by participants and the risk of food-borne outbreaks. Key messages Define the most frequent microrganisms could be associated with backed food and evaluate which one of these can exceed the dose for the occurrence of disease in long time. Reflect on the likelihood that the risk of food-borne outbreak caused by manipulation of happy hour participants, may result in an increase in hospital admissions.

The new effect of neodymium magnet (NdFeB) on storage quality of potatoes

Modern techniques of potato tubers storage have a number of economic, technical, and technological disadvantages and they don’t ensure high product safety - potato losses run up to 30 % per storage season. The work has been conducted on the effect of magnetic field of neodymium (NdFeB) magnet on sprouting, weight loss and storage of potatoes because this method is the most interesting and understudied. The equipment used in the research: equipment for magnetic potato treatment, NdFeB magnets, magnetometer is used to identify positive and negative magnetic poles, and auxiliary instruments. As a result of the experimental studies it has been found that untreated potatoes had weight loss of 39 %. Weight loss of potatoes treated with positive magnetic field of 330…350 mT and time treatment 60…180 s was 4 %. The positive magnetic field of 330…350 mT was effective in suppressing sprout growth. It is also to inhibit sprout growth in potatoes stored at 25°C. Potatoes receiving more than 330…350 mT dose, were higher in length of sprouts, and higher weight loss of potatoes (20…50 %). Also, potatoes receiving negative magnetic field dose, were higher in length of sprouts, and higher weight loss (60 %) than those given positive magnetic field dose. As a result of experiments, the design of a new device for magnetic processing of potatoes has been developed. It is anticipated that magnetic fields influence the potato cells, as the result of the effects, potato tubers either lock in moisture, starch and other substances, or lose them quickly due to inner-structure destruction.

Comparative demography elucidates the longevity of parasitic and symbiotic relationships.

Parasitic and symbiotic relationships govern vast nutrient and energy flows, yet controversy surrounds their longevity. Enduring relationships may engender parallel phylogenies among hosts and parasites, but so may ephemeral relationships when parasites colonize related hosts. An understanding of whether symbiont and host populations have grown and contracted in concert would be useful when considering the temporal durability of these relationships. Here, we devised methods to compare demographic histories derived from genomic data. We compared the historical growth of the agent of severe human malaria, Plasmodium falciparum, and its mosquito vector, Anopheles gambiae, to human and primate histories, thereby discerning long-term parallels and anthropogenic population explosions. The growth history of Trichinella spiralis, a zoonotic parasite disseminated by swine, proved regionally specific, paralleling distinctive growth histories for wild boar in Asia and Europe. Parallel histories were inferred for an anemone and its algal symbiont (Exaiptasia pallida and Symbiodinium minutum). Concerted growth in potatoes and the agent of potato blight (Solanum tuberosum and Phytophthora infestans) did not commence until the age of potato domestication. Through these examples, we illustrate the utility of comparative historical demography as a new exploratory tool by which to interrogate the origins and durability of myriad ecological relationships. To facilitate future use of this approach, we introduce a tool called C-PSMC to align and evaluate the similarity of demographic history curves.

Transient decreases in methylation at 5'-cCGG-3' sequences in potato (Solanum tuberosum L.) meristem DNA during progression of tubers through dormancy precede the resumption of sprout growth.

The 5-methylcytosine (5mC) content in DNA of tuber meristems isolated from field-grown potatoes (Solanum tuberosum L.) was determined during a 7-month storage period at 3 degrees C for three growing/postharvest seasons. No significant changes in 5mC levels were noted genome-wide or within 5'-CG-3' dinucleotide sequences, 5'-CG-3' islands or 5'-CA(T)G-3' trinucleotide sequences during storage. However, a consistent but transient 50-70% decrease in methylation at both cytosines within 5'-CCGG-3' sequences was detected that peaked 112-194 days after harvest. This result was corroborated by methylation-sensitive amplified fragment length polymorphism analysis of meristem DNA. Similar to tuber meristems undergoing progression through natural dormancy, premature chemical termination of dormancy resulted in rapid, transient 5'-CCGG-3' demethylation in meristem DNA. Minimum methylation levels at this sequence preceded initiation of high levels of de novo DNA synthesis by two days. Cytosine methylation status was also followed in in vitro-generated potato microtubers during 7 months of post-harvest storage. As in DNA from tuber bud meristems, no changes in genome-wide 5mC content or methylation at 5'-CA(T)G-3' or 5'-CG-3' island sequences were noted in microtuber DNA. However, there was a transient 46% drop in methylation at 5'-CG-3' dinucleotides concomitant with minimum levels of 5'-CCGG-3' methylation (30-60% below those in dormant microtubers) 57-98 days after harvest. As microtubers exited dormancy, there were sustained three- and seven-fold increases in RNA and DNA synthesis rates, peaking on or after 98 days of storage, respectively. Together, these data demonstrate that demethylation of 5'-CCGG-3' sequences occurs independently of tuber age during dormancy progression and precedes transcriptional activation of genes leading to cell division and meristem growth in potatoes.

Influence of temperature shifts on survival, growth, and toxin production by psychrotrophic and mesophilic strains of Bacillus cereus in potatoes and chicken gravy

A study was done to determine the influence of temperature on growth and toxin production characteristics of psychrotrophic and mesophilic strains of Bacillus cereus when inoculated into mashed potatoes and chicken gravy containing various concentrations of sodium chloride and held at temperatures different from those at which cells had been cultured. Logarithmic growth phase cells (10 h, 30°C) of psychrotrophic (F3802A/84) and mesophilic (B4ac-1) strains of Bacillus cereus were inoculated into rehydrated commercially processed instant mashed potatoes and chicken gravy supplemented with 0, 2, or 4% sodium chloride. Growth, survival, and diarrheal toxin production in potatoes and gravy held at 30, 37, and 10°C (strain F3802A/84) or 30, 40, and 10°C (strain B4ac-1) were monitored. Both strains grew in both foods containing no added sodium chloride or 2% sodium chloride when held at 30, 37, or 40°C for 2 days. Strain B4ac-1 grew better than strain F3802A/84 in foods containing 4% sodium chloride. Maximum amounts of enterotoxin (1024 ng/g) were produced by strain B4ac-1 in chicken gravy held at 30 and 40°C. Strain F3802A/84 grew to populations of 7 log 10 CFU/g in foods containing no added sodium chloride or 2% sodium chloride at 10°C. Strain F3802A/84 produced the highest amount of enterotoxin (1024 ng/g) at 30°C in chicken gravy containing 0.7 or 2% sodium chloride; however, little or low amounts of toxin (4–16 ng/g) were produced in chicken gravy at 10°C. Compared to strain B4ac-1, cells of strain F3802A/84 subjected to a downward shift in incubation temperature (10°C) grew more rapidly in chicken gravy. Strain B4ac-1 produced the highest amount of toxin (1024 ng/g) at 30°C in gravy containing 4% sodium chloride and at 40°C in gravy containing 0.7% sodium chloride. Toxin was not detected in inoculated mashed potatoes. Results of this study indicate that shifts in incubation temperature influence growth and toxin production by psychrotrophic and mesophilic strains of B. cereus differently. It is important to store pasteurized, ready-to-eat foods at a temperature low enough to prevent the growth of B. cereus.

Effects of fosthiazate and aldicarb on populations of plant‐growth‐promoting bacteria, root‐lesion nematodes and bacteria‐feeding nematodes in the root zone of potatoes

A 2‐year study investigated the relationship between the nematicides aldicarb and fosthiazate and populations of plant growth‐promoting (PGP) and plant‐growth‐inhibiting (PGI) bacteria, and root‐lesion nematodes and bacteria‐feeding nematodes in the root‐zone soils of potatoes. Fewer (P < 0.05) bacterial genera and species were recovered from aldicarb‐treated soils than from the fosthiazate and untreated soils but bacterial population densities were greatest in the aldicarb‐treated soils. In potato plantlet bioassays using root‐zone bacteria from the three soil sources, bacteria from the aldicarb‐treated soils reduced (P < 0.01) the mean wet and dry weight of shoots and roots compared with those from the fosthiazate and untreated soils. In the field, fosthiazate (but not aldicarb) significantly increased tuber yields and reduced nematode population densities of Pratylenchus penetrans in roots and soil. Population densities of bacteria‐feeding nematodes (primarily Diplogaster lheritieri) were not affected by either nematicide. Aldicarb appeared to suppress the populations of plant‐growth‐promoting bacteria that contribute to enhanced growth in potatoes. This is attributed to the long‐term use of aldicarb at the trial site, which may have encouraged the selection, or adaptation, of soil microorganisms that degrade carbamate pesticides but do not enhance potato growth.

Effect of Pot Size and Timing of Plant Growth Regulator Treatments on Growth and Tuber Yield in Greenhouse-Grown Norland and Russet Burbank Potatoes

The effects of pot size, timing of the applica- tion of paclobutrazol (PTZ) and gibberellic acid (GA3), and the counteractive effect of these two compounds on growth and tuber yield of greenhouse-grown Norland and Russet Burbank potatoes were investigated. Plants were grown either in 1.5-liter pots (15 cm deep) or 3.0- liter pots (18 cm deep) and received a foliar application of either 1.5 mM PTZ or 9◊1 0 ˛3 mM GA3 at early or late stolon initiation. Some plants that had been foliar treated with 1.5 mM PTZ at early stolon initiation were foliar treated wit h9◊1 0 ˛3 mM GA3 at late stolon initiation. PTZ reduced haulm length in both cultivars significantly, particularly when the treatment was applied at early sto- lon initiation, but the late treatment reduced haulm length only when growing in 3.0-liter pots. Irrespective of the timing of treatment, GA 3 increased haulm length in Nor- land growing in both pot sizes, but the treatment in- creased haulm length in Russet Burbank only when ap- plied at late stolon initiation. GA 3 applied after PTZ did not overcome the growth-inhibiting effect of the PTZ treatment. The PTZ treatment effectively increased us- able tuber number/plant (UTN) in Norland, but PTZ had no effect on UTN in Russet Burbank. PTZ reduced us- able tuber weight/plant (UTW) only in Norland growing in 1.5-liter pots. By contrast, GA3 increased UTN only when treated at late stolon initiation of 1.5-liter pot- grown Norland, whereas the same treatment was effec- tive when applied only at early stolon initiation for Rus- set Burbank. For Norland, the increase in UTN by early applied PTZ was reduced by the subsequent application of GA 3 . The use of 3.0-liter pots for minituber produc- tion in both Norland and Russet Burbank appears to have no advantage over growing in 1.5-liter pots, particularly when PTZ or GA3 is used to enhance tuberization.

The influence of solid urban waste compost and nitrogen‐mineral fertilizer on growth and productivity in potatoes

The influence of solid urban waste (SUW) compost and nitrogen (N)‐mineral fertilizer on the growth and productivity in semi‐early harvest potatoes (Solanum tuberosum L, var. ‘Edzina') was studied over a period of three years. Nine treatments derived from a factorial combination of 3 levels of SUW compost (0, 18, 36 T#lbha‐1) and 3 levels of N‐mineral fertilizer (0, 125, 250 Kg N ha‐1) were carried out on a sandy, moderately fertile plot. The applications of SUW compost and N‐mineral fertilizer showed a stimulation in plant development with respect to the non‐treated controls. The mineral fertilizer treatment gave markedly higher results. Plant response to the combined mineral fertilizer‐compost treatments demonstrated a tendency towards saturation within each level of application. Potato productivity results indicated that this crop reacts strongly and positively to an application of N‐mineral fertilizer, but only slightly to the treatment levels of compost considered in the study. As a consequence of the application of SUW compost, the application‐response graphs reveal a reduction in the optimal levels of N‐mineral fertilizer application and an increase in the efficacy of the mineral fertilizer.

Optimization of Conditions for In vitro Pollen Germination and Tube Growth in Potatoes

We have optimized the in vitro conditions for germination and tube growth of potato pollen, primarily that of tetraploid cv. Borka, in suspension culture under constant aeration and pollen density. Optimal concentration of H3BO3 and sucrose were 0.8 mM to 3.2 mM and 15%, respectively. Lactose and polyethyleneglycol (PEG 1000) were superior to sucrose in promoting pollen germination and tube growth, while substitution of sucrose with raffinose, maltose, glucose, galactose, fructose, or mannitol did not improve medium for germination. The best results were achieved with 20% PEG 1000 and 2% sucrose at 1.6 mM H3BO3. The superiority of the PEG medium was confirmed in three dihaploid genotypes. Calcium nitrate at 0.1 and 1 mM inhibited pollen germination and tube growth, and the inhibitory effect on germination was much stronger with sucrose than with PEG. No differences were found in germination rates and tube growth at pollen densities 0.5 and 1.5 mg mL-1 but increasing the density to 3 mg mL-1 reduced germin...

Phasic Temperature Change Patterns Affect Growth and Tuberization in Potatoes

This study determined the responses of potato (Solanum tuberosum L., cv. Norland) plants to various patterns of air temperature changes over different growth periods (phasic temperature changes). In each of two experiments under controlled environments, eight treatments of temperature changes were carried out in two growth rooms maintained at 17 and 22C and a constant vapor pressure deficit of 0.60 kPa and 14-hour photoperiod. Plants were grown for 63 days after transplanting of tissue culture plantlets in 20-liter pots containing peat-vermiculite mix. Temperature changes were imposed on days 21 and 42, which were essentially at the beginning of tuber initiation and tuber enlargement, respectively, for this cultivar. Plants were moved between two temperature rooms to obtain eight temperature change patterns: 17-17-17, 17-17-22, 17-22-17, 22-17-17, 17-22-22, 22-17-22, 22-22-17, and 22-22-22C over three 21-day growth periods. At harvest on day 63, total plant dry weight was higher for the treatments beginning with 22C than for those beginning with 17C, with highest biomass obtained at 22-22-17 and 22-17-17C. Shoot dry weight increased with temperature increases from 17-17-17 to 22-22-22C during the three growth periods. Tuber dry weight was highest with 22-17-17C, and lowest with 17-17-22 and 17-22-22C. With 22-17-17C, both dry weights of stolons and roots were lowest. Total tuber number and number of small tubers (<2.5 cm) were highest with 17-17-17 and 17-17-22C, and lowest with 17-22-22 and 22-22-22C, whereas number of medium tubers (2.5-5.0 cm) was highest with 22-17-22C, and number of large tubers (>5.0 cm) was highest with 22-17-17C. This study indicates that tuber development of potatoes is optimized with a phasic pattern of high temperature during early growth and low temperature during later growth.

The influence of temperature on leaf development and growth in potatoes in controlled environments

SummaryThree controlled environment experiments were conducted at different temperatures to determine the relation between temperature and leaf development and growth in the potato (cv. Maris Piper). Developmental stages are defined for the appearance and duration of leaf extension in the potato and comparisons made with other temperate zone crops.The rate of leaf appearance was linear over the temperature range (9–25°C) and above 25°C there was no further increase in the rate. The temperature coefficient for the rate of appearance of leaves was 0.032 leaves (degree days)‐1 using a base temperature of 0°C. The duration of extension of an individual leaf decreased with increase in temperature up to 25°C such that the thermal duration was constant at 170 degree days using a base temperature of 0°C for leaf positions 4–10 on the main stem. At higher leaf positions the thermal duration was similar or greater. The advantages and limitations of controlled environment work as a parallel to field experimentation are discussed.

NH4/NO3 MIXTURES ENHANCE GROWTH IN POTATOES

The effects of various NH4-N/NO3-N ratios on growth and mineral accumulation in potatoes (Solanum tuberosum cv. Norland) were investigated using a nutrient film technique. Plants were grown for 35 days after transplanting at six NH4-N/NO3-N mixtures of 0/100%, 20/80%, 40/60%, 60/40%, 80/20%, and 100/0% with the same total N concentration of 4 mM. All mixed N treatments significantly increased total and tuber dry weights, plant size, leaf area, and specific leaf area as compared to either NH4 or NO3 alone. Plant growth was better with NO3 alone than with NH4 alone. Compared with mixed N treatments, total N concentrations in shoots were lower with either N form alone whereas total N in roots was lower only with NO3 alone. With increased percentages of NH4, root nitrate N concentrations decreased, and reduced N increased. The NO3 alone treatment increased concentrations of Ca, Mg, Fe and Mn, and reduced concentrations of P, S, Cl, B, Zn and Cu in shoots as compared with NH4 and mixed N treatments. It is concluded that a proper maintenance of both NH4 and NO3 forms can potentially promote growth and yield in potatoes.

Temperature Cycling Periods Meet Growth and Tuberization in Potatoes under Continuous Irradiation

Plants of the potato (Solanum tuberosum L.) cultivars Denali, Norland, Haig and Kennebec were grown for 42 days under three temperature cycling periods (thermoperiods) with continuous irradiation in two repeated experiments to help determine if temperature cycling might be varied to optimize tuber development of potatoes in controlled environments. Thermoperiods of 6/6 hours, 12/12 hours and 24/24 hours were established with the same temperature change of 22/14C and same controlled vapor pressure deficit of 0.60 kPa. The thermoperiod of 24/24 hours significantly promoted tuber initiation but slowed tuber enlargement in all four cultivars, compared to the thermoperiods of 6/6 hours and 12/12 hours. Denali' produced the highest tuber and total dry weights under the 6/6 hours thermoperiod. Kennebec' produced the highest tuber dry weight under the 12/12 hours thermoperiod. Thermoperiods had no significant effect on shoot and root dry weights of any cultivars. The major effect of thermoperiods was on initiation and enlargement of tubers.

Potassium concentration effect on growth, gas exchange and mineral accumulation in potatoes.

This study was conducted to evaluate the responses of potatoes to six K solution concentrations maintained with a flow-through nutrient film system. Potato plants were grown for 42 days in sloping shallow trays containing a 1 cm layer of quartz gravel with a continuous flow of 4 ml min-1 of nutrient solutions having K concentrations of 0.10, 0.55, 1.59, 3.16, 6.44, 9.77 meq L-1. Plant leaf area, total and tuber dry weights were reduced over 25% at 0.10 meq L-1 of K and over 17% at 9.77 meq L-1 of K compared to concentrations of 0.55, 1.59, 3.16 and 6.44 meq L-1 of K. Gas exchange measurements on leaflets in situ after 39 days of growth demonstrated no significant differences among different K treatments in CO2 assimilation rate, stomatal conductance, intercellular CO2 concentration, and transpiration. Further measurements made only on plants grown at 0.10, 1.59, 6.44 meq L-1 of K showed similar responses of CO2 assimilation rate to different intercellular CO2 concentrations. This suggested that the photosynthetic systems were not affected by different K nutrition. The leaves of plants accumulated about 60% less K at 0.10 meq L-1 of K than at higher K concentrations. However, Ca and Mg levels in the leaves were higher at 0.10 meq L-1 of K than at higher K concentrations. This indicates that low K nutrition not only reduced plant growth, but also affected nutrient balance between major cations.

Effect of triacontanol on sprout growth in potatoes (Solanum tuberosum)

AbstractThe effects of a 3‐min dip in various concentrations (0–1–100 mg litre−1) of a triacontanol emulsion on sprout growth from single‐eye pieces of seed potato (Solanum tuberosum L) tubers were assessed after 10 days' growth in acid‐washed sand. Treatment effects were compared with those resulting from immersion for 3 min in a mixture of gibberellic acid (6 mg litre−1) and ethrel (4 mg litre−1).Triacontanol dips were more effective than gibberellic acid and ethrel. Treatments increased the fresh weight of sprouts but had little effect on sprout number per tuber fragment. The optimum concentration of triacontanol was 10 mg litre−1.

Effects of crop husbandry and growing conditions on storage losses of Pentland Crown potatoes

SUMMARYOver five growing seasons (1976–80) experiments were carried out using at least three contrasting sites per season to study the relationship between growing conditions and storage losses in Pentland Crown potatoes. Crops were harvested by hand and storage was carried out in a single environment over a period of 6–7 months without sprout suppressants. The range in growing conditions was great and reflected in the pattern of leaf growth and range in yields of the stored crops (30–90 t/ha). Crops from Tenby (S. W. Wales) produced the most consistent and frequently the highest yields and usually lost the least weight during storage. Although the range in total weight loss over all experiments was large from 5·4 to 16·3%, treatment effects were much smaller than in field growth and yield. Delaying the date of harvest usually increased weight loss and tubers harvested in early August stored at least as well as late-harvested tubers. Tubers harvested without prior defoliation stored as well as tubers harvested on the same day from crops defoliated at least 2 weeks previously. Lengthening the interval from defoliation to harvest usually increased weight loss in storage. Although the tubers were hand harvested effects on saleability were found at the end of storage and there was no evidence that earlier harvesting, which may involve some loss of field yield, would result in any loss of saleable yield out of store.The results provided no evidence to support the widely-held view that the suitability of a tuber for harvesting improves during maturation associated with natural or imposed crop senescence. It is therefore suggested that the use of the term maturity be avoided as it is wholly unhelpful in studies of the relationship between field growth and storage losses in potatoes.

Nitrogen fertilizer recommendations for arable crops as based on soil analysis

The present paper is a review of previous work by the senior author [5, 6, 7, 8]. As demonstrated by experimental results for winter wheat, potatoes and sugar beet, soil tests for mineral nitrogen in early spring may be looked upon as a means of better assessing optimum fertilizer nitrogen requirements in commercial farming. A second soil test, at the onset of growth in potatoes and sugar beet, may be useful in considering nitrogen topdressings. It is recognized, however, that soil mineral nitrogen data do not provide a full explanation for the variation in optimum nitrogen dressings and other soil or climatic factors may be involved.

Leaf Growth, Tuber Growth, and Water Potential in Potatoes1

The objective of this study was to measure the effect of plant water deficit on the growth of potato (Solanum tuberosum L. ‘Russet Burbank’) leaves and tubers. Changes in leaf length, in tuber weight and dimension, and in leaf water potential were measured in glasshouse‐grown potatoes during drying cycles. Leaf elongation rate declined as leaf water potential decreased, and leaf growth ceased at water potentials between −4 and −5 bars. Field measurements of leaf elongation agreed with glasshouse results. Measurements of tuber weight, and of tuber length and diameter, indicated that tuber expansion also ceased at about −4 to −5 bars. These results are discussed in relation to the diurnal changes in leaf and tuber water potentials observed under field conditions.