Temperature,cyanide, and oxygen effects on the respiration,chip color,sugars, and organic acids of stored tubers

The possibility that sugar accumulation of potatoes stored at low temperatures may be linked to activation of cyanide-resistant respiration (CRR) was investigated. After a lag period of several days, continuous HCN treatment stimulated CO₂ production of tubers stored in 20% O₂. At 1°C in 20% O₂, HCN treatment increased respiration over that effected by low temperature treatment. After several weeks of treatment, cyanide-stimulated CO₂ production was greater at 1°C than at 10°C. Sucrose and malate levels of HCN treated tubers were sometimes higher than those of the 10°C control tubers, but they were always lower than those of the 1°C control tubers. This indicated that CRR alone could not account for the sugar increases at 1°C. Storage in 2% O₂ blocked the increase in CO₂ production and changes in constituents associated with HCN treatments in 20% O₂. HCN treatment had no significant effect on chip color. The level of CRR was measured in freshly cut slices from Monona, Norchip, and Kennebec tubers previously stored at 10°, 5°, or 1°C for several months. Slices from tubers previously stored at 1°C had increased CRR, but there was no difference in CRR between the 5°C and 10°C treatments. Sugars accumulated at 5°C, again indicating that sugar accumulation in potatoes stored at low temperatures was at least partially independent of the activation of CRR.     

The effect of 2,4-d on tuberization and starch content of potato tubers produced on stem segments culturedin vitro

The effect of 2,4-D on tuberization, yield and the starch content of potato tubers produced on stem segments was examined. Potato stem segments were cultured in nutrient agar containing 2,4-D concentrations ranging from 10^?7 M to 2 × 10^?3 M. The stem segments were incubated in the dark at 25° C and examined after 15 days. The degree of tuberization on stem segments cultured in media containing 10^?7 M and 10^?6 M 2,4-D was higher than on the control stem segments. Mainly long stolons were observed on stem segments cultured in media containing 10^?4 M and 2 × 10^?3 M 2,4-D. The percent starch (dry wt. basis) in stolons was higher than that in tubers. However, the total starch content of tubers per stem segment cultured in media containing 10^?7 M and 10^?6 M 2,4-D was significantly higher than that of stolons obtained from stem segments cultured in media containing higher concentrations of 2,4-D. The total starch content of tubers, except those produced on stem segments cultured in media containing 10^?7 M 2,4-D, decreased steadily with increasing concentration of 2,4-D in the culture media.     

Effects of free air carbon dioxide enrichment and nitrogen supply on growth and yield of winter barley cultivated in a crop rotation

The increase in atmospheric CO₂ concentration [CO₂] has been demonstrated to stimulate growth of C₃ crops. Although barley is one of the important cereals of the world, little information exists about the effect of elevated [CO₂] on grain yield of this crop, and realistic data from field experiments are lacking. Therefore, winter barley was grown within a crop rotation over two rotation cycles (2000 and 2003) at present and elevated [CO₂](375 ppm and 550 ppm) and at two levels of nitrogen supply (adequate (N2): 262 kg ha⁻¹ in 1st year and 179 kg ha⁻¹ in 2nd year) and 50% of adequate (N1)). The experiments were carried out in a free air CO₂ enrichment (FACE) system in Braunschweig, Germany. The reduction in nitrogen supply decreased seasonal radiation absorption of the green canopy under ambient [CO₂] by 23%, while CO₂ enrichment had a positive effect under low nitrogen (+8%). Radiation use efficiency was increased by CO₂ elevation under both N levels (+12%). The CO₂ effect on final above ground biomass was similar for both nitrogen treatments (N1: +16%; N2: +13%). CO₂ enrichment did not affect leaf biomass, but increased ear and stem biomass. In addition, final stem dry weight was higher under low (+27%) than under high nitrogen (+13%). Similar findings were obtained for the amount of stem reserves available during grain filling. Relative CO₂ response of grain yield was independent of nitrogen supply (N1: +13%; N2: +12%). The positive CO₂ effect on grain yield was primarily due to a higher grain number, while changes of individual grain weight were small. This corresponds to the findings that under low nitrogen grain growth was unaffected by CO₂ and that under adequate nitrogen the positive effect on grain filling rate was counterbalanced by shortening of grain filling duration.     

Effect of controlled atmosphere,temperature and cultivar on sprouting and processing quality of stored potatoes

Summary Three crisping potato cultivars, Record, Saturna and Hermes, were stored at 5 or 10°C in gas mixtures of either 0.5% CO₂ and 21.0% O₂ (control) or 9.4, 6.4, 3.6 or 0.4% CO₂ all combined with 3.6% O₂. There was almost complete sprout inhibition, low weight loss and maintenance of a healthy skin for all cultivars stored in 9.4% CO₂ with 3.6% O₂ at 5°C for 25 weeks. When tubers from this treatment were stored for a further 20 weeks in air at 5°C the skin remained healthy and they did not sprout. The fry colour of crisps made from these potatoes was darker than the industry standard but when they were reconditioned, tubers of cv. Saturna produced crisps of an acceptable fry colour while crisps from the other two cultivars remained too dark. Reducing sugar levels were related to fry colour both after storage and after reconditioning. The other gas combinations and the controls did not have the same effect on sprouting and none of the controlled atmosphere treatments controlled sprouting at 10°C.     

Yield formation of CO2-enriched hybrid rice cultivar Shanyou 63 under fully open-air field conditions

Hybrid indica rice (Oryza sativa L.) cultivars play an important role in rice production system due to its heterosis, resistance to environmental stress, large panicle and high yield potential. However, no attention has been given to its yield responses to rising atmospheric [CO₂] in conjunction with nitrogen (N) availability. Therefore we conducted a free air CO₂ enrichment (FACE) experiment at Yangzhou, Jiangsu, China (119°42′0′′E, 32°35′5′′N), in 2004–2006. A three-line hybrid indica rice cv. Shanyou 63 was grown at ambient and elevated (ca. 570 μmol mol⁻¹) [CO₂] under two levels of supplemental N (12.5 g Nm⁻² and 25 g Nm⁻²). Elevated [CO₂] had no effect on phenology, but substantially enhanced grain yield (+34%). The magnitude of yield response to [CO₂] was independent of N fertilization, but varied among different years. On average, elevated [CO₂] increased the panicle number per square meter by 10%, due to an increase in maximum tiller number under enrich [CO₂], while productive tiller ratio remained unaffected. Spikelet number per panicle also showed an average increase of 10% due to elevated [CO₂], which was supported by increased plant height and stem dry weight per tiller. Meanwhile, elevated [CO₂] caused a significant enhancement in both filled spikelet percentage (+5%) and individual grain weight (+4%). Compared with the two prior FACE studies on rice, hybrid indica rice cultivar appears to profit much more from elevated [CO₂] than japonica rice cultivar (ca. +13%), not only due to its stronger sink generation, but also enhanced capacity to utilize the carbon sources in a high [CO₂] environment. The above data has significant implication with respect to N strategies and cultivar selection under projected future [CO₂] levels.     

The effect of controlled atmosphere storage at 4°C on crisp colour and on sprout growth,rotting and weight loss of potato tubers

Summary After three weeks curing at 10°C, potato tubers cv. Record were stored at 4°C under different controlled atmospheres (CA) for six months to study the effect on crisp fry colour, sprout growth and rotting. Combinations of low levels of CO₂ (0.7–1.8%) and low levels of O₂ (2.1–3.9%) gave a significantly lighter crisp colour, low sprout growth and fewer rotted tubers compared with 0.9% CO₂ and 21.0% O₂. Tubers stored in these conditions. showed a significantly higher weight loss and shrinkage after reconditioning. High CO₂: low O₂ combinations during storage completely inhibited sprout growth and caused the darkest crisp colour, but after reconditioning tubers gave the same level of sprouting and crisps as light as the other CA combinations. Furthermore these combinations, especially CO₂ at 10 or 15%, increased the onset of rotting. Also our results showed that at low concentrations of CO₂ (0.7–1.6%), and low O₂ (2–2.4%) there was an increase in tuber rotting.     

氮肥和密度互作对冬小麦石4366群体、茎秆特性和产量的影响

为探索施氮量和种植密度互作对冬小麦品种石4366生长特性的影响,2020-2021年度在长期氮肥定位试验田通过裂区试验,设置4个施氮水平(施氮量分别为75 kg·hm^-2、150 kg·hm^-2、225kg·hm^-2和300 kg·hm^-2,分别用N75、N150、N225和N300表示)和5个种植密度水平(分别为225×10⁴株·hm^-2、300×10⁴株·hm^-2、375×10⁴株·hm^-2、450×10⁴株·hm^-2和525×10⁴株·hm^-2,分别用D225、D300、D375、D450和D525表示),比较分析了不同处理间该品种旗叶面积、穗部发育、群体动态、秸秆特性和产量的差异。结果表明,施氮量和种植密度对石4366群体、茎秆特性和产量均有显著影响。N75条件下穗长、总小穗...     

A System for the Measurement of Vertical Gradients of CO2, H2O and Air Temperature within and above the Canopy of Plant

Absract

This technical report describes a gradient system for characterizing the vertical gradients of CO₂, H₂O, and air temperature within and above the canopy of plants. The system is low in cost and easy to use. The instruments were fitted and placed in one box with a total weight of about 10 kg. The box can be carried and moved from one site to another. The features of this apparatus are high frequency sampling cycle as short as 1 min per cycle for all six measurement levels and fast response gas analyzer for measurement as short as 10s per level. Two exhaust pumps, one sampling pump, six 3-way solenoid valves, and flow meter were used to insure simultaneous flow rate of air in all tubes from all measurement levels. This system transfers data from the data-logger directly to the add-in Spreadsheet of Microsoft Excel by using an Ethernet cable to automatically convert digital data to scientific units in less time. This system also allows the use of multiple micro-environmental sensors that can be sampled at the same time. It is useful not only for agricultural ecosystems but is also adequately sensitive and rapidly responds to the gas analyzer with a modifiable flow rate meter for use in forest ecosystems. This system also has potential for use in the measurement of CO₂, H₂O, associated environmental elements, and CO₂ storage flux within the canopy of plant, and other processes including a CO₂ sink and source.     

Selection for 2n gametes and tuberization inSolanum chacoense

A breeding scheme is outlined which broadens the genetic base of the potato by incorporation of germplasm fromS. chacoense (Argentina) with Group Phureja and haploids of Group Tuberosum. Selection for adaptation to cultivation and production of 2n gametes is carried out at the diploid level, with the benefits of disomic ratios.S. chacoense provides increased genetic diversity, vegetative vigor and profuse flowering. About one-fifth of the 654 plants examined produced 2n eggs; clones with high 2n egg production may be obtained either by screening within particular introductions or by intercrossing known 2n egg producers. Only 16 of 1,212 plants screened produced 2n pollen —one by first division restitution. There is great variation among introductions and individuals for tuberization in the greenhouse. Selection for early tuberization in the field may be difficult due to extremely long stolons, but it would be facilitated by incorporation of the short stolon characteristic from the topiary mutant typeS. infundibuliforme. Male sterile Tuberosum haploids hybridize withS. chacoense to give male fertile interspecific F₁ progeny, some of which produce 2n eggs or 2n pollen.     

不同小麦进化材料生育后期的光合特性及其对环境因子响应的比较

为了解不同小麦近缘材料光合特性,以二倍体节节麦、四倍体硬粒小麦、六倍体普通小麦、八倍体小黑麦为材料,在生育后期测定了其光合气体交换参数、叶绿素含量、叶面积指数等光合相关性状,并对净光合速率在不同光照、CO_2浓度、温度、湿度条件下的变化进行了分析。结果表明,八倍体小黑麦的光合气体交换参数和叶绿素含量比其他三个材料高,六倍体小麦在叶面积上具有明显优势;四倍体和六倍体小麦具有较高的光能利用效率,而二倍体小麦和八倍体小黑麦对强光的抗性较强;六倍体小麦和八倍体小黑麦对CO_2的利用率和抗逆性都较强;八倍体小黑麦的光合速率受温度的影响较小,而二倍体和四倍体小麦的光合速率受温度的影响比较大;二倍体小麦的光合速率受湿度的影响较大,四倍体小麦的光合速率受湿度的影响较小,六倍体小麦和八倍体小黑麦光合速率在高湿条件下变化较小。这说明不同小麦近缘种具有不同的光合特性,是小麦进行小麦高光合育种的重要基因资源。     

Intra-specific variation of wheat grain quality in response to elevated [CO2] at two sowing times under rain-fed and irrigation treatments

In order to investigate the intra-specific variation of wheat grain quality response to elevated atmospheric CO₂ concentration (e[CO₂]), eight wheat (Triticum aestivum L.)cultivars were grown at two CO₂ concentrations ([CO₂]) (current atmospheric, 389 CO₂ μmol mol⁻¹vs. e[CO₂], FACE (Free-Air CO₂ Enrichment), 550  ±  10% CO₂ μmol mol⁻¹), at two water levels (rain-fed vs. irrigated) and at two times of sowing (TOS₁, vs. TOS₂). The TOS treatment was mainly imposed to understand whether e[CO₂] could modify the effects of timing of higher grain filling temperatures on grain quality. When plants were grown at TOS₁, TKW (thousand kernel weight), grain test weight, hardness index, P, Ca, Na and phytate were not significantly changed under e[CO₂]. On the other hand, e[CO₂] increased TKW (16%), hardness index (9%), kernel diameter (6%), test weight (2%) but decreased grain protein (10%) and grain phytate (11%) at TOS₂. In regard to grain Zn, Mn and Cu concentrations and some flour rheological properties, cultivar specific responses to e[CO₂] were observed at both sowing times. Observed genetic variability in response to e[CO₂] in terms of grain minerals and flour rheological properties could be easily incorporated into future wheat breeding programs to enable adaptation to climate change.     

Simulation of the effects of genotype and N availability on rice growth and yield response to an elevated atmospheric CO2 concentration

The objective of this study was to identify physiological processes that result in genotypic and N fertilization effects on rice yield response to elevated atmospheric CO₂ concentrations ([CO₂]). This study conducted growth and yield simulations for 9 rice genotypes grown at 4 climatically different sites in Asia, assuming the current atmospheric [CO₂] (360 ppm) and elevated [CO₂] (700 ppm) using 5 levels of N fertilizer (4, 8, 12, 16, 20 g m⁻² N fertilizer). A rice growth model that was developed and already validated for 9 different genotypes grown under 7 sites in Asia was used for the simulation, integrating additional components into the model to explain the direct effect of [CO₂] on several physiological processes. The model predicted that the relative yield response to elevated [CO₂] (RY, the ratio of yield under 700 ppm [CO₂] to that under 360 ppm [CO₂]) increased with increasing N fertilizer, ranging from 1.12 at 4 g m⁻² N fertilizer to 1.22 at 20 g m⁻² N fertilizer, averaged overall genotypes and locations. The model also predicted a large genotypic variation in RY at the 20 g N treatment, ranging from 1.08 for ‘WAB450-I-B-P-38-HB’ to 1.41 for ‘Takanari’ averaged overall locations. Combining all genotypes grown at the 5N fertilization conditions, a close 1:1 relationship was predicted between RY and the relative [CO₂] response in spikelet number for crops with a small number of spikelets (less than 30,000 m⁻²) under the current atmospheric [CO₂] (n = 18, r = 0.89^***). In contrast, crops with a large number of spikelets under the current atmospheric [CO₂] showed a significantly larger RY than the relative [CO₂] response for spikelet number per unit area. The model predicted that crops with a larger number of spikelets under the current atmospheric [CO₂] derived great benefit from elevated [CO₂] by directly allocating increased carbohydrate to their large, vacant sink, whereas crops with a smaller number of spikelets primarily required an increased spikelet number to use the increased carbohydrate to fill grains. The simulation analyses suggested that rice with a larger sink capacity relative to source availability under the current atmospheric [CO₂] showed a larger yield response to elevated [CO₂], irrespective of whether genotype or N availability was the major factor for the large sink capacity under the current [CO₂]. The model predicted that the RY response to nitrogen was brought about through the N effects on spikelet number and non-structural carbohydrate accumulation. The genotypic variation in RY was related to differences in spikelet differentiation efficiency per unit plant N content. Further model validation about the effects of [CO₂] on growth processes is required to confirm these findings considering data from experimental studies.     

The Effect of Elevated Atmospheric CO2 Concentration on Two Populus Clones Grown in a FACE System

SUMMARY

Two poplar clones, hybrid Populus deltoides Bartr. Ex Marsh X Populus nigra L. (Populus xeuramericana), clone I-214, and Populus deltoides, clone Lux, were grown from hardwood cuttings for one growing season in either ambient (360 μmol mol^?1) or elevated (560 μmol mol^?1) [CO₂] in FACE-systemrings at Rapolano Terme (Siena, Italy). Both clones I-214 and Lux exhibited a higher aboveground bio-mass, photosynthesis at light saturation and instantaneous transpiration efficiency (ITE) in CO₂-enriched air. The elevated [CO₂]-induced responses of clone I-214 included increased investment in branch and leaf biomass, and enhanced stem volume. The elevated [CO₂]-induced responses of clone Lux included an increase in the number of branches (and foliage area). Indication of photosynthetic acclimation under elevated [CO₂] was found during the early morning, but only in clone I-214. Stomatal conductance decreased under elevated [CO₂] particularly in clone Lux. Clone differences in response to elevated [CO₂] should be taken in account when planning future poplar plantations in forecast warmer and drier Mediterranean sites.     

Changes in Freezing Tolerance and its Relationship with the Contents of Carbohydrates and Proline in Overwintering Centipedegrass (Eremochloa ophiuroides (Munro) Hack.)

Abstract

The objective of this study was to clarify the changes in the contents of endogenous carbohydrates and proline in the stolons and leaves of centipedegrass (Eremochloa ophiuroides (Munro) Hack.), during the natural cold acclimation (hardening) and de-acclimation (dehardening) in relation to freezing tolerance in the field at the transition zone between temperate and subtropical areas in China. The contents of carbohydrates and proline, and freezing tolerance estimated by LT₅₀, which is the temperature at which 50% of the electrolytes in the organ was measured in the leachate, were determined at 10-day intervals from October 1, 2001 to April 18, 2002. It was indicated that the freezing tolerance of stolons increased (LT₅₀ of stolons decreased) quickly, as temperature dropped before winter, but that of leaves which senesced along with the drop in temperature did not. The freezing tolerance of stolons decreased gradually along with the rise in temperature above 5 °C in spring, when the overwintered plants started to grow. The contents of proline and soluble carbohydrates, including sucrose, fructose and glucose, increased as LT₅₀ decreased when temperature dropped below 5 °C before winter, and decreased as LT₅₀ increased in early spring. Correlation analysis revealed that the freezing tolerance of stolons of centipedegrass significantly and positively correlated with the contents of proline and soluble carbohydrates, and the ratio of the soluble carbohydrates to starch. Thus, the freezing tolerance of stolons, which are critical organs that determine the winter surviving ability, largely depended on the content of soluble carbohydrates and the ratio of soluble carbohydrates to starch in centipedegrass. The possible relationship between freezing tolerance and carbohydrate metabolism was also discussed.     

Effect of CO2 Concentration,Temperature and N Fertilization on Biomass Production of Soybean Genotypes Differing in N Fixation Capacity

Abstract

We tested the hypothesis that elevated CO₂ concentration [CO₂]-induced enhancement of biomass production of soybean is greater in a genotype that has a higher nitrogen (N) fixation capacity. Furthermore, we analyzed theinteractive effects of N fertilization, temperature and [CO₂] on biomass production. Three genetically related genotypes: Enrei (normally-nodulating genotype), Kanto 100 (supernodulating genotype), and En1282 (non-nodulating genotype) were grown in pots, with or without N fertilizer for two years (2004, 2005). They were then subjected to two different [CO₂] (ambient and elevated (ambient + 200 ?mol mol-¹)) × two temperature regimes (low,high (low + 4~5ºC)). Top dry weight at maturity was the greatest in the elevated [CO₂] × high temperature regime, irrespective of genotype and N fertilization. The [CO₂] elevation generally enhanced N acquisition and dry matter production during the vegetative growth stage, and the enhancement was more pronounced in the nodulating genotypes (Enrei and Kanto 100) than in the non-nodulating genotype (En1282), indicating that N supply through N fixation contributes to elevated [CO₂]-induced biomass production in soybean. However, the relative responsiveness ofbiomass production to elevated [CO₂] was not necessarily higher in the supernodulating genotype than the normally-nodulating genotype. The N utilization efficiency to produce biomass was inferior in the supernodulating genotype than in the normally-nodulating and non-nodulating genotypes. These results did not fully verify the hypothesis that elevated [CO₂]-induced enhancement of biomass production of soybean is greater in a genotype with a higher N fixation capacity.     

Comparative Efficacy of CO2 and Ozone Gases Against Ephestia cautella (Lepidoptera: Pyralidae) Larvae Under Different Temperature Regimes

Comparative efficacy of three different modified atmospheres: 100% CO₂, 75% CO₂ + 25% N₂, and 22 ppm ozone were examined against larval mortality of the almond moth, Ephestia cautella (Walker) (Lepidoptera: Pyralidae) at temperature regimes of 25°C and 35 ± 2°C and 60 ± 5% relative humidity, and 9:15 dark and light. Wandering young larval instars, which are fast growing, large enough in size and considered as more tolerant to modified atmosphere, were collected directly from the rearing culture, placed inside pitted date fruits of vars.: “Khudri,” “Ruziz,” and “Saqie,” were treated with aforementioned gases for 24, 48, and 72 h. The immediate and delayed larval mortality was recorded after each exposure timing. Ozone possessed the strongest fumigant toxicity causing 100% mortality with all varieties, at 25 and 35°C after 24 h exposure and was more effective than 75% CO₂ that caused 83 and 100% immediate mortality with variety ruziz at 25 and 35°C, respectively. Extending the treatments exposure time to 72 h, 100% mortality was recorded by exposing larvae to any of the studied gases at 25 and 35°C. These results suggest that gases and temperature used in this study can be effectively used to control E. cautella in dates and stored grains.     

Interactive Effects of CO2 and O3 on the Growth of Trisetum flavescens and Trifolium pratense Grown in Monoculture or a Bi-Species Mixture

SUMMARY

Golden oat grass (Trisetum flavescens L.) and red clover (Trifolium pratense L.) were grown as monocultures or bi-species mixtures under controlled conditions and exposed to ambient (350 ppm) or elevated (580 ppm) CO₂, with or without addition of O₃ (diel profile with 150 ppb maximum). Shoot biomass measurements after the initial growth and two re-growth periods were used to determine the specific responses of both species, and the difference in the specific response between monocultures and mixtures. T. pratense was much more responsive to CO₂, O₃, and their combination, compared to T. flavescens. In the case of O₃ but not of CO₂, the difference in sensitivity between species was larger in mixture than in monoculture. In contrast to elevated CO₂, O₃ significantly reduced the root:shoot ratio in the mixture, which could explain the increasing negative effect of O₃ on clover with progressing harvests.

The relative CO₂ stimulation of T. pratense and of the cumulative mixture shoot biomass was larger in the presence than in the absence of O₃, which was due to an almost complete protection from O₃ stress by elevated CO₂. In the mixture, the fraction of T. flavescens was small and increased during the experiment; this increase was most pronounced with O3, but any change in mixture biomass was dominated by the response of T. repens.

The results confirm that in grass/legume mixtures legumes are most sensitive to elevated CO₂ and O₃, but the magnitude of specific responses depends on canopy structure and of plant development. Elevated CO₂ minimizes the negative impacts of O₃ stress on above- and below-ground plant growth.     

The influence of storage factors on endogenous ethylene production by potato tubers

Throughout a 7-month storage period, Russet Burbank tubers continuously ventilated at 32 F (0 C) and 45 F (7.2 C) with atmospheres of 2% O₂, air, 4% CO₂, and intermittently ventilated with air, evolved ethylene at a rate no greater than 0.008 μ 1 Kg^?1 hr^?1. Tubers stored in 80% O₂ and 12% CO₂ produced ethylene at much higher rates. In all cases where sprouting occurred, the rate of ethylene production increased. Inoculation withFusarium roseum greatly stimulated ethylene production but inoculation withAlternaria solani did not.     

Accelerated drying of cut lucerne (Medicago sativa L.) by chemical treatments based on inorganic potassium salts or alkali metal carbonates

Liquid treatments to accelerate drying were applied to lucerne under laboratory conditions by brief immersion (～3s) of cut shoots. Aqueous solutions of the alkali metal carbonates Li₂CO₃, Na₂CO₃ and K₂CO₃ were found to reduce drying times to 33% moisture content (MC) on a dry weight basis (dwb) by 45%, 55% and 65% respectively. Effectiveness was related to the ionic radius of the cation. From a range of potassium salts (KCl, K₂CO₃, KHSO₄, KOH, K₂SO₄) in aqueous solution, the only useful reductions in drying time to 33% MC (dwb) came from the alkaline KOH (68%) and K₂CO₃ (65–76%). It is considered that K⁺ has a specific function in increasing water loss through the plant cuticle and that association with CO₃^2- provides the high pH necessary for this activity. An aqueous solution of K₂CO₃ (0·16 M) gave greater acceleration of drying than the organic solvent petroleum ether and no benefit was gained by combining these treatments. Addition of a surfactant did not improve the effectiveness of K₂CO₃ as a desiccant but mixing with a rape-seed oil emulsion reduced the drying time to 33% MC (dwb) by 11% relative to K₂CO₃ alone. Under field conditions K₂CO₃ as an aqueous solution gave only small reductions in the drying time to 33% MC and effectiveness was reduced by the addition of the rapeseed oil emulsion. Better results with K₂CO₃ (aq) might have been achieved with a more ventilated swath structure but the results strongly suggest that the oilseed rape emulsion is unlikely to improve the effectiveness of K₂CO₃ under field conditions.     

The influence of storage on the physiology and productivity of Kennebec seed potatoes

Kennebec seed potatoes were stored in various atmospheres of O₂ and CO₂ at 32 and 41 F (0 and 5 C). Samples were removed every 6 weeks for measurement of bud and parenchyma tissue respiration, rate of ion loss from tissue sections and reducing sugar content. Potatoes remaining at the end of the storage period were warmed, cut and planted immediately in a randomized complete block design for yield evaluation. Intact tuber respiratory rates were higher at 32 F than 41 F. Increasing CO₂ increased respiratory rates and decreasing O₂ decreased respiratory rates at both temperatures. Decreasing O₂ concentration significantly decreased reducing sugar at both 32 and 41 F. Increasing CO₂ significantly increased reducing sugar at 41 F but not at 32 F. Kennebec potatoes did not tolerate added CO₂ at 32 F but did survive 4% CO₂ at 41 F. Reducing oxygen decreased the tolerance to CO₂. The onset of carbon dioxide injury was not clearly evident from changes in bud and parenchyma tissue respiration or in loss of electrolytes from cut tissue sections. However, CO₂ accelerated tuber breakdown by unidentifiedFusarium Spp. No significant differences in yield were observed between treatments that survived the storage period.