The Dependence of Net Assimilation Rate on Leaf-area Index

The leaf-area index (leaf area per unit area of land, L) offield crops of kale and sugar-beet was varied experimentallyby removing different fractions of the plant population distributeduniformly through the crop. The net assimilation rate (E) wasdetermined in subsequent periods of 10–14 days. For kale, E decreased nearly linearly with increase of L throughoutthe range from I to 5. E of sugar-beet was less affected bychange in L and was apparently not decreased until L rose aboveabout 3. Because of this dependence of E on L, the rate of dry-matterproduction per unit area of land, or crop growth-rate (C=EL),showed a curved relation to L; for kale it increased to a maximumwhen L was between 3 and 4 and fell again at higher values ofL. Maximal C for sugar-beet occurred beyond the range of L tested,probably between L=6 and L=9. This optimal L for dry-matterproduction by sugar-beet crops probably lies near the upperlimit of the current agricultural range, so there is little,if any, scope for increasing the dry-matter yield by furtherincrease in L. For heavy kale crops L is already far in excessof the optimum, and it may be possible to increase the totaldry-matter yield of kale by repeated thinning or defoliationto hold L near the optimum.     

Effect of Temperature on Net Assimilation Rate

Net assimilation rates and other growth attributes were comparedfor rape, sunflower, and maize plants growing widely spacedat temperatures of 10°, 16°, 22°, 28°, and 34°C, in light of 3, 000 f.c. intensity. The optimum temperature for net assimilation rate lay between20° and 30° C, and was lowest for rape and highest formaize. The temperature coefficient of the net assimilation ratewas lower than that of the relative growth-rate, especiallyin rape and sunflower, corresponding to an increase in leaf-arearatio with in temperature. This arose to an increase in leaf-arearatio with rise in temperature. This mcrease arose through changeinleafarea/leaf weight; temperature had little effect on leafweight/plant weight. In moderate to warm conditions the net assimilation rate variedlittle with temperature: by only± 10 per cent between12° and 30° C for rape, and 23° and 36° C formaize. This agrees with observations in natural climates whichsuggest that temperature is generally less important than lightin controlling net assimilation rates, except in cool climates.In natural climates, as in these controlled climates, relativegrowth-rate is more temperature-dependent.     

Effects of Age and Environment on Net Assimilation Rate of Barley

To distinguish between the effects of age and environment onnet assimilation rate (E) of barley (var. Brant) grown in theopen in pots at Ottawa, E was measured outdoors (treatment N)and on similar plants transferred to a constant environmentfor the 2 weeks during which E was determined (treatment T).During June and July, E of treatment N decreased by 77 per cent.;for treatment T this fall increased to 90 per cent, of the initialvalue. E and average day and night temperatures were greaterin the constant environment than outdoors in early June, andin July they were greater outdoors. Incident light energy wasalways greater outdoors. Thus, the fall in E with age was partiallymasked outdoors by an increase caused by the improvement inenvironmental conditions during the experiment. Plants grown continuously in the constant environment had lowerE, greater leaf area and dry weight, and ears emerged earlierthan plants of similar age that had been transferred for 2 weeksto the constant environment from outdoors. E of plants growncontinuously in the constant environment decreased with time,both when the pots were moved away from the light panel to maintaina constant light intensity at the base of the youngest leafand when the pots remained stationary so that the plants grewtowards the lights. After ears emerged, E for treatments N and T was measured onplants whose ears were shaded to prevent them photosynthesizing.Photosynthesis in the ear accounted for 19 per cent, of thefinal ear dry weight during the first 2 weeks after emergence,12 per cent, during the 3rd and 4th, and 3 per cent, duringthe 5th and 6th weeks. Shading had no effect on weight of plantparts other than ears and had similar effects outdoors and inthe constant environment.     

The Influence of Carbohydrate and Mineral Nutrient Supply on the Growth of Potato Tubers

The uptake and distribution of nitrogen, phosphorus, and potassiumhas been studied throughout the life of potato plants. Thereappears to be a net loss of all three elements from the plantduring emergence growth even though uptake occurs. When daughtertubers are formed they very quickly become the dominant sinkfor mineral nutrients, the concentrations of N, P, and K remainingsteady for a long period. These concentrations are maintainedin spite of decreasing rates of uptake, indicating the transferenceof mobile ions from the haulm to the growing tubers. ¹⁴C tracer experiments have shown that after tuberization thereis a greater export of recently incorporated photosynthate fromthe leaves than takes place before tuberization. There is nogood correlation between the size of individual tubers and theamount of photosynthate transported into them. This is thoughtto be because the largest tubers are not necessarily growingfaster than the smaller tubers. The most active sinks are alsomost active in converting the mobile ¹⁴C into storage compounds.The mother tuber continues to import ¹⁴C until it is detachedfrom the plant, but over much of this period there is no changein the tuber dry-weight, indicating that there is an equivalentexport from the tuber. The similarities between these distribution patterns and thosefound in tubers showing second-growth are described and theimplications with respect to the control of tuber growth discussed.     

Influence of Tops and Roots on Net Assimilation Rate of Sugar-beet and Spinach Beet and Grafts between them

Sugar-beet has a larger storage root and greater net assimilationrate (E) than spinach beet. To determine whether the greaterroot was a result or cause of the greater E, grafts were madebetween tops and roots of sugar-beet and spinach-beet in allfour possible combinations. Grafted plants with sugar-beet roots had greater E and rootdry weight, less leaf area and top dry weight and lower concentrationof sugar in the leaf lamina, than those with spinach-beet roots,irrespective of the type of top. Grafted plants with sugar-beettops had greater E, total and root dry weight, but less leafarea, than those with spinach-beet tops, irrespective of thetype of root. The difference in E between grafted plants withsugar-beet tops and spinach-beet tops was similar to that betweengrafted plants with sugar-beet roots and spinach-beet roots.It increased with time to 60 per cent. Increases in E probably represent increases in rate of photosynthesis.Sugar-beet roots probably increased photosynthesis by providinga better sink for assimilates than spinach-beet roots.     

Dependence of Net Assimilation Rate on Root Growth of Isolated Leaves

The phenomenon of inhibition of assimilation by carbohydrateaccumulation has been reinvestigated using single rooted leavesof dwarf bean. Such a system has the advantage that assimilatingarea remains constant and carbohydrate is translocated to asingle sink-the root system. The net assimilation rate of thesystem did not vary with season and was small compared withintact plants in the summer, suggesting that an internal factorcontrols assimilation rate. Evidence is given that this factoris the rate of translocation of carbohydrate from source tosink (from lamina to root) which in turn depends on growth-rateof the root system. The evidence came from experiments in whichroot growth was stimulated by increasing vessel size, by preliminarytreatment with IAA or by raising the root temperature, or wasretarded by kinetin treatment. In experiments at glasshouse temperature, lamina dry matterincreased by 0.75 mg. per cm.² per week. The maximum valuesattained depended on the time of the experiment. In August itwas greater than 7.0 mg. per cm.¹, but there was a seasonaltrend. In experiments with roots at 24?C, carbohydrate accumulatedin the lamina more slowly than at lower temperatures.     

High Net Assimilation Rates of Sunflower Plants in an Arid Climate

Net assimilation rates of sunflower plants (Heliantkus annuus),grown widely spaced with soil nutrients and water non-limiting,reached 2.0 g dm^–3 wk^–1 in clear weather at midsummerin an arid climate. These rates exceed all previously recordedand are roughly double those hitherto taken to be maximal insunflower. They suggest that maximum rates of photosysnthesisin the most active leaves were 50–65 mg CO₂ dm_–2h_–1. These high rates are a response to the high levels of radiationin the arid climate. They imply that (given non-limiting soil)plants can attain higher productivity in the arid climate thanin any other.     

马铃薯生育期和干物质积累的动态模拟研究

根据三年的田间试验数据和有关气象资料,提出了马铃薯生育期和干物质积累的模拟模型、用高斯方程计算每天的温度条件对马铃薯生育期和干物质积累的生理效应,改进了前人的生育期模型和温度条件对干物质积累影响系数的计算方法．以每天的单位叶面积变化、群体上方的有效辐射和温度变化模拟群体的干物质积累、结果表明,本研究的模型有明确的机理性和较高的精度．用Visual Basic 6．0界面表达每日生态条件变化对群体光合生产和干物质积累的影响,模拟结果具有直观的机理性,从而克服了同类研究中的缺陷。     

Nutrient Concentrations and Interactions in Young Leaves of Potato Plants Growing With and Without Tubers

Potato plants (King Edward) were grown in soil in buckets underglass. Sampling young leaves showed that giving potassium initiallyincreased the magnesium concentration in leaf dry matter butdecreased it after the tubers started to form. Removing tubershad little effect on this change and did not prevent changesthat occurred in leaf potassium, phosphorus and calcium concentrations,suggesting that the partitioning of nutrients between shootgrowth and tuber growth was not regulated simply by competition. Removing the tubers or giving potassium increased the totallife of the haulm, by 50 and 27 d respectively. Tuber removallessened water use but giving potassium increased it, probablybecause it resulted in larger plants. Removing the tubers causedabnormal growths from axillary buds and thickened starchy stembases; the latter were augmented by giving potassium.     

The Effect of Gamma-Irradiation on the Sucrose Content in Sweet Potato Roots and Potato Tubers

The sucrose content in both potato tubers and sweet potato roots was considerably increased by gamma-irradiation. The maximum increase was achieved by an irradiation dose of 3 to 4 kGy for potatoes and 0.8 to 2 kGy for sweet potatoes. Cooling treatment (15°C, 2 weeks) for sweet potato roots also enhanced the sucrose content (almost 2 times) but was not additive to the irradiation treatment; the maximum sucrose content in irradiated sweet potato roots was in the range of 7 to 12% irrespective of the cooling treatment, depending on the variety of sweet potatoes. Irradiation made the sucrose content in the roots 2 to 4 times higher.     

二级水灌溉对土壤及马铃薯块茎中大肠菌群数量的影响

采用多管发酵法检测二级水灌溉对马铃薯种植土壤中大肠菌群数量,结果表明:充分灌溉后的土壤中大肠菌群的数量均高于分根交替灌的土壤;地下滴灌的土壤中大肠菌群数量高于沟灌土壤的大肠菌群数量;二级水经加氯消毒后,土壤中大肠菌群数量明显下降。同样采用多管发酵法检测马铃薯块茎,结果发现:采用加氯消毒后的二级水灌溉的小区E和F中生长的马铃薯,其块茎组织中大肠菌群数量低于其他小区,采用地下滴灌灌溉的小区I和J所种植出的马铃薯块茎中大肠菌群的数量高于采用沟灌灌溉的小区K和L。结果表明:马铃薯块茎中大肠菌群的数量与其生境中大肠菌群的数量有密切关系。     

马铃薯干物质分配与器官建成的动态模拟研究

根据多年不同保护地栽培田间试验的结果,利用Origin软件结合马铃薯生长发育的基本特点,提出了以发育生理日为驱动变量的光合产物在不同器官间分布的数值模型,方法简便,机理明确,模拟精度高.研究还给出了不同发育时期马铃薯不同器官的干物率变化模型,并依此推导出器官的鲜重模型,进行了马铃薯块茎产量的模拟,结果表明模拟值与实测值具有良好的一致性。     

The Influences of Jasmonic Acid Methyl Ester on Microtubules in Potato Cells and Formation of Potato Tubers

Amides in a CH₂Cl₂ extract from the fruits of Piper retrofractum were detected by HPLC/APCI-MS. Seven new unsaturated amides, together with six known ones, were isolated, and their structures were determined to be N-isobutyl-2E,4E,12Z-octadecatrienamide (1), N-isobutyl-2E,4E,14Z-eicosatrienamide (2), 1-(octadeca-2E,4E,12Z-trienoyl)piperidine (3), 1-(eicosa-2E,4E,14Z-trienoyl)piperidine (4), 1-(octadeca-2E,4E-dienoyl)piperidine (5), 1-(eicosa-2E,4E-dienoyl)piperidine (6), and 1-(eicosa-2E,14Z-dienoyl)piperidine (7) on the basis of chemical and spectroscopic evidence.     

Detection of Potato Tuber-Inducing Activity in Potato Leaves and Old Tubers

Potato tuberization is induced under short days but substancewhich triggers it is still unknown. Tuber-inducing activitywas detected in leaves and old tubers using single-node stemsegment culture in vitro as a bioassay method. The activityin leaves increased under short days, but remained almost constantunder long days. It was also found in physiologically old tubers.Anion exchange chromatography of the ethanol extract gave aneluate that exhibited strong tuber-inducing activity. Partialpurification revealed the presence of two kinds of active substances,one of which seemed to be a glycoside of the other. These substancesappear to be different from known plant hormones. (Received October 19, 1987; Accepted June 9, 1988)     

Sucrose Synthetase of Rice Grains and Potato Tubers

ABSTRACT

Human coagulation factor XII, the initiating factor in the intrinsic coagulation pathway, is critical for pathological thrombosis but not for hemostasis. Pharmacologic inhibition of factor XII is an attractive alternative in providing protection from pathologic thrombus formation while minimizing hemorrhagic risk. Large quantity of recombinant active factor XII is required for screening inhibitors and further research. In the present study, we designed and expressed the recombinant serine protease domain of factor XII in Pichia pastoris strain X-33, which is a eukaryotic expression model organism with low cost. The purification protocol was simplified and the protein yield was high (~20 mg/L medium). The purified serine protease domain of factor XII behaved homogeneously as a monomer, exhibited comparable activity with the human βFXIIa, and accelerated clot formation in human plasma. This study provides the groundwork for factor XII inhibitors screening and further research.     

Effect of Arachidonic Acid on Potato Tubers during Storage

Potato (Solanum tuberosumL.) tubers were treated with various concentrations (10^–9to 10^–4M) of biogenic elicitor arachidonic acid during storage (from October to June). The data showed that the resistance-inducing concentration of arachidonic acid was 10^–6M in autumn and 10^–9M in spring. The possible causes of the change in the immunizing concentration of arachidonic acid during storage of potato tubers are discussed.     

The Production, Storage, and Translocation of Carbohydrates in Developing Potato Plants

¹⁴C-tracer experiments showed that the export of assimilateslabelled with a short pulse of ¹⁴CO₂ continued for 5 weeks.There appeared to be an approximately exponential loss of ethanol-insoluble¹⁴C from the haulm with a half-time of about 3.5 weeks. Initiallythere was a poor correlation between the fresh weight of thetubers and their ¹⁴C content but the correlation became goodafter 5 weeks. Field data showed that, in many instances, the rate of tubergrowth was greater than the rate of growth of the whole plant.This suggests the transfer of large amounts of dry matter fromthe haulm to the tubers. Dry-matter loss from the haulm couldaccount for the discrepancy and the amount transferred in thisway was about 10 per cent of the final dry weight of the tuber. There was an increase in net assimilation rate when the leafarea of the plants started to decline. It is suggested thatthis increase was due to an increase in the rate of photosynthesisbrought about by the influence of the rapidly growing tubers.     

Probability of Globodera rostochiensis Spread on Equipment and Potato Tubers

The probability of spreading cysts of Globodera rostochiensis on farming equipment and potato tubers was investigated in naturally infested field plots. The number of cysts recovered from soil that adhered to equipment differed significantly between different pieces of equipment. These differences were related to initial nematode density and, in most cases, to the volume of soil that adhered to the equipment. At an initial density of 0.04 egg/cm³ of soil, significantly more cysts were recovered from a potato digger than from a potato hiller, cultivator, or plow. At an initial density of 0.90 egg/cm³ of soil, significantly more cysts were recovered from the plow than from the other equipment. Although the population density was 22 times greater, only 10 times more cysts adhered 3 to equipment used in soil with a density of 0.90 egg/cm³ of soil than when used in soil infested at 0.04 egg/cm³. The number of potato tuber samples (4.5 kg) that contained cysts with viable eggs was positively correlated with the initial densities of G. rostochiensis in soil in which they were produced. The percentage of tuber samples with cysts containing viable eggs was 10-12% for tubers harvested from soil with densities less than 1 egg/cm³ and 30-76% for tubers harvested from soil with densities greater than 4 eggs/cm³ of soil.