Effects of potassium nutrition on the glycolysis and the krebs cycle in taro plants

The previous works (1, 2) with the bleeding sap from taro plants showed that a potassium deficiency altered the amplitude and the period of the diurnal periodicity in exudation process with the roots, and suggested that potassium might be an essential element for an intensive exchange of amino acids between living xylem tissues and xylem sap. The other works (3,4) with excised roots from sweet potato plants grown in a seven days solution culture showed that the relatively K-deficient roots had higher respiratory activities than the normal, especially In the root tip, and accumulated concomitantly higher levels of reducing sugars and amino nitrogen. Recently, however, an increasing number of works (5, 6) has been devoted exclusively to elucidating the relationship between respiratory activity in plant tissues and organic acid metabolism under a relative K-deficiency. In this work the effects of potassium nutrition on the glycolysis and the Krebs cycle in the roots and the leaves of taro plants are investigated in an attempt to compare these effects in a longer term culture of taro plants with those in a seven days culture of sweet potato plants.     

The growth and the respiration in roots of sweet potato plants under a moderate potassium deficiency

A seven days' culture of sweet potato plants under a deficient potassium application induced various metabolic disturbances in the roots (1,2) and the leaves (3). Prolonged cultures of taro (4), broad bean plants (5), and barley (5) suggested that a half level of the normal potassium content in roots might be a critical point of K -deficiency resulting in a higher respiration rate than its normal status. Such a temporary enhancement of respiration accompanied by accumulation of amino-N and reducing sugars may not necessarily contribute to the accumulation and the assimilation of salts, but accelerate the disturbance of plant metabolism to cause early death of the tissues. This work deals with supplemental data on the effects of K -deficiency on the plant growth and the respiration in roots, comparing these effects in a 15 days' culture of sweet potato plants with those in a longer term culture of other plant species (4,5).     

The respiration in the roots of broad bean and barley under a moderate potassium deficiency

The previous work on the respiration in taro plants (1) suggests that superior activities of the glycolysis and the Krebs cycle in these plant tissues under a moderate K-deficiency may be reduced a) with advancing plant maturation, b) with extended K-deficiency, or c) with increasing damage in the metabolism itself, due to unfavourable treatments. Thus the question arises where a critical point of potassium deficiency resulting in a higher respiration rate compared with its normal status should be set up in each plant species, giving careful consideration to the physiological and environmental conditions of the plant concerned. This work was undertaken in an attempt to compare the effects of potassium nutrition on the respiration in the roots of broad bean and barley with those in a longer term culture of taro plants (1).     

Glycolic acid oxidase activity in crop plant leaves

Many workers have revealed the possible role of glycolic acid oxidase in the photosynthesis and the respiration of plant leaves (1, 5) and in the organic acid metabolism of rice plant roots (6). There is also abundant evidence that α-hydroxysulfonates, the bisulfite addition compounds of aldehydes and ketones, are the specific and competitive inhibitors of the enzyme (7, 8). The pevious works (9, 10) showed that a deficient application of potassium increased the content of amino-N and reducing sugars and concomitantly the respiratory activity in sweet potato roots. Such a derangement in the metabolic status of plant roots would be expected to be intimately connected with any changes in the photosynthesis and the respiration of the leaves. This paper, as a preliminary, describes some results from investigations into the glycolic acid oxidase activity in leaves of rice plant- and barley seedlings, sweet potato plants, and taro plants which were grown in solution culture at varying potassium application : the effects of light and plant age on enzyme activity, the activation of the enzyme by FMN addition, the stability of the enzyme during a prolonged incubation of sap from leaves, and the inhibitory effects of specific inhibitors on the enzyme in vitro and in vivo.     

干旱胁迫下钾素对甘薯碳水化合物及内源激素含量的影响

【目的】研究干旱胁迫下施钾量对不同生长时期甘薯碳水化合物及内源激素含量的影响,为甘薯的抗旱高产栽培提供理论依据。【方法】选用食用型甘薯品种‘泰中6号’为材料,以硫酸钾（K₂SO₄）为供试肥料,水分处理设土壤最大持水量的60%～70%和30%～40%,依次代表正常供水（W1）和干旱胁迫（W0）;钾肥设K0、K1、K2、K3四个水平,K₂O用量分别为0、120、240和360 kg/hm2。分析了不同生长时期甘薯干物质含量、淀粉和可溶性糖含量、内源激素含量及收获期块根产量。【结果】干旱胁迫下甘薯植株干物质含量、块根和淀粉产量显著降低,施钾有利于甘薯植株干物质含量的提高、块根的膨大和淀粉的生成和积累,甘薯植株和块根干物质含量、块根淀粉含量和积累量最大均为K2处理,较K0提高幅度最大分别达到31.7%、43.6%、10.6%和50.6%。相同钾用量条件下,干旱胁迫下块根单薯重显著高于正常灌水,单株结薯数显著低于正常灌水。正常灌水条件下施钾后甘薯叶片可溶性糖含量降低,而块根可溶性糖含量升高,干旱胁迫下施钾使甘薯叶片和块根可溶性糖含量增大,较K0提高幅度最高分别达到31.4%和36.0%。干旱胁迫下施钾后甘薯叶片和块根IAA、ABA、ZR和GA含量显著增大,较K0提高幅度最高分别达到12.7%、15.7%、12.0%、10.4%和21.4%、15.6%、65.7%、13.0%,促进了甘薯植株碳水化合物含量和干重的提高,块根淀粉积累速率增大。【结论】干旱胁迫下施钾促进了干物质向块根的分配,提高了甘薯块根单薯重,从而增加了单位面积甘薯块根产量。干旱胁迫下钾素提高甘薯块根和叶片内源激素（ABA、IAA、ZR、GA）含量,块根内源激素含量的增加促进了块根淀粉的合成和积累,叶片内源激素含量的增加促进了地上部茎叶生长、茎叶干物质积累和叶片可溶性糖含量的增加,增强了甘薯的抗旱性。     

腐植酸缓释钾肥对土壤钾素含量和甘薯吸收利用的影响

利用腐植酸和硫酸钾制备一种腐植酸钾肥(HA-K),沙柱淋溶试验结果表明其对钾素具有一定的缓释作用。为阐明施用腐植酸缓释钾肥对土壤不同形态钾素含量的影响,在田间小区试验条件下,研究了腐植酸缓释钾肥对土壤不同形态钾素含量以及甘薯产量和对钾素吸收利用的影响。结果表明:与不施钾（空白对照）相比,施用腐植酸促进了甘薯对钾素的吸收,降低了甘薯全生育期土壤中的速效钾和缓效钾含量以及生长前期土壤有效钾含量,但是提高了甘薯生长中、后期土壤有效钾含量。与施等量氧化钾对照相比,施用腐植酸缓释钾肥促进了甘薯对钾素的吸收,降低了甘薯全生育期土壤缓效钾含量和甘薯生长前、中期土壤速效钾和有效钾的含量,提高了甘薯生长后期土壤速效钾和有效钾的含量。与施等量氧化钾对照相比,施用腐植酸缓释钾肥显著提高了钾肥吸收利用率(REK)、农学利用率(AEK)、偏生产力(PFPK)和甘薯块根产量,增幅分别为20.09 %,42.69 %,5.89%和22.83%。     

钾素对食用型甘薯糖代谢相关酶活性的影响

为了探讨钾素提高甘薯块根可溶性糖含量的生理基础。选用典型的食用型甘薯品种北京553,设置不同施钾处理,于2009～2010年2个生长季在山东农业大学农学试验站进行试验。采用甘薯块根膨大过程中定期取样的方法,测定块根可溶性糖和淀粉含量及相关酶活性、功能叶蔗糖含量及相关酶活性。结果表明,与对照比较,施用钾肥能显著提高块根产量、可溶性糖及各糖组分含量,其中K2O用量为24 g/m2处理增幅最大,为最适用量。进一步研究发现,适宜供钾处理显著提高了功能叶磷酸蔗糖合成酶活性和蔗糖含量,生育期内平均增幅分别为10.31%和34.13%,同时提高了块根中蔗糖合成酶、不溶性酸性转化酶的活性,生育期内平均增幅为16.47%和3.66%,在提高源端光合产物供应的同时促进蔗糖在库端的卸载,促进块根中淀粉和可溶性糖的积累;适宜供钾处理还提高了块根中-和-淀粉酶的活性,生育期内平均增幅分别为26.06%和14.64%,促进淀粉向可溶性糖转化。此外,适宜供钾处理还显著提高了生长前期和后期块根中可溶性酸性转化酶活性、以及生长后期块根中蔗糖-蔗糖果糖基转移酶活性,促进了葡萄糖、果糖和果聚糖在块根中的积累。在甘薯收获期,块根可溶性糖和淀粉含量分别提高了13.52%和3.02%。即钾肥能够增加块根中蔗糖的供应量、促进块根对蔗糖的吸收、促进淀粉水解,是其提高块根可溶性糖含量的生理原因。     

Root respiration and bacterial population of roots I. Effect of nitrogen source,potassium nutrition and aeration of roots

Spring wheat was grown in nutrient solution culture to investigate the influence of aeration, different sources of nitrogen and discontinuation of potassium supply on root respiration and on the number of root bacteria. By definition root respiration included oxygen consumption of the excised roots and their microbial colonizers. Root respiration was subject to diurnal variations. It was low towards the end of the dark period and increased within two hours during the light period. Independent of the nutrient supply the respiration rate and bacterial number were considerably higher in unaerated than in aerated nutrient solution. Root respiration was lowest when using nitrate as a source of nitrogen and highest with ammonium nutrition. Intermediate respiration rates were obtained for mixed nitrogen nutrition. Respiration corresponded to the bacterial colonization of the roots. The discontinuation of potassium supply led in plants supplied with nitrate to an insignificant increase in root respiration, whereas a marked increase in respiration was observed in plants with mixed ammonium and nitrate nutrition. In contrast, Root respiration of plants supplied with ammonium declined when potassium was discontinued. Discontinuation of potassium supply caused an increase in root respiration and bacterial numbers in both aerated and unaerated media.     

钾营养对甘薯某些生理特性和产量形成的影响

田间试验结果表明 ,适量供钾可增加甘薯功能叶和块根中的ATP含量 ,增加块根中的脱落酸 (ABA)含量 ;提高叶片中可溶性碳水化合物的装载效率和块根中可溶性碳水化合物的卸载效率 ,促进碳水化合物由叶片向块根的运输 ;增加块根中的淀粉含量 ,提高块根干重与单株干重的比率 ,促进块根迅速膨大 ,增加块根产量     

湿度对甘薯愈伤的影响

为探索湿度对甘薯愈伤的影响,本试验以普薯32号甘薯为原料,人工模拟机械损伤后于25℃、不同相对湿度(RH50%和RH80%)条件下愈伤,通过比较甘薯木质素生成、失重率、呼吸强度、愈伤过程关键酶活性、总酚和类黄酮含量的差异,评价湿度对甘薯愈伤的影响。结果表明,RH80%条件下较RH50%更有利于甘薯愈伤木栓组织的形成,在愈伤4 d时甘薯木质素积累达到最高。与RH50%组相比,RH80%条件处理能显著提高甘薯愈伤组织苯丙氨酸解氨酶(PAL)、过氧化物酶(POD)和多酚氧化酶(PPO)活性(P<0.05),提升总酚、类黄酮含量,促进呼吸高峰提前,降低甘薯重量损失。相关性分析表明,RH80%条件下愈伤,甘薯木质素含量与PAL、POD、PPO活性及总酚、类黄酮含量呈显著正相关(P<0.05)。本研究结果为甘薯采后愈伤提供了一定的理论依据。     

花生-甘薯轮作制中磷钾肥施肥模型研究

本文探讨了花生-甘薯轮作制中钾肥和磷钾肥施肥模型的建立方法。通过裂区田间试验设计,建立了钾肥和磷钾肥当季施肥模型和甘薯后效模型以及甘薯当季施肥模型。3个钾肥试验和2个磷钾肥试验结果表明,上述模型能很好地拟合田间试验结果。后效模型可计算出花生磷钾肥最佳施用量下对甘薯的后效产量,甘薯当季肥效模型可求得扣除肥料残留效应后的磷钾肥最佳施用量,降低了甘薯推荐施肥量,提高了施肥效益。     

Nitrogenous constituents of bleeding sap from taro plants grown in nitrate nutrition under a potassium deficiency

The previous work (1) with bleeding sap from taro plants grown in solution culture at varying ammonium sulphate application under aerobic condition revealed that a potassium deficiency led to a contradictory relationship of the variation in amino-N content in bleeding sap to the exudation rhythm; in the earlier period of bleeding experiment a deficient K-application decreased the amino-N content but accelerated the exudation rate. In this connection, there are good reasons for believing that the passage of water and salts into the xylem ducts is largely controlled by the metabolic conditions in adjacent living cells, especially their rate of aerobic respiration (2). Therefore, the effects of potassium nutrition on the exudation phenomenon were reexamined with taro plants grown in solution culture under nitrate nutrition and correlated with information about the effect of aeration through culture medium during bleeding experiment on the rate of exudation and contents of nitrogenous constituents of bleeding sap. Arsenite- or DNP-treatment was also carried out in vivo with the roots in order to elucidate a possible relationship between the respiration in roots and the exudation process of xylem sap.     

干旱胁迫与正常供水钾肥影响甘薯光合特性及块根产量的差异

【目的】干旱胁迫影响甘薯叶片光合特性及块根产量,研究通过施肥缓解干旱胁迫机理可为甘薯抗旱高产栽培提供理论依据。【方法】选用食用型甘薯品种“泰中6号”为材料,以硫酸钾(K2SO4)为供试肥料,水分处理设为土壤最大持水量的60%~70%(正常供水W1)和30%~40%(干旱处理W0); 钾肥设K0、 K1、 K2、 K3四个水平,K2O用量分别为0、 12.0、 24.0和36.0 g/m2。分析不同钾肥用量对不同生长时期甘薯叶片相对含水量、 叶绿素荧光参数、 光合特性及收获期块根产量的影响。【结果】在干旱胁迫和正常灌水条件下,施钾处理均显著增加了甘薯叶面积和叶片叶绿素含量,提高净光合速率(Pn),增加光合产物的生产和积累,提高块根产量和收获指数。两种水分条件下,块根产量均以K2处理最高, 干旱胁迫下K2与K3处理差异显著,正常灌水处理不显著。两种水分条件下,甘薯叶片光合参数对钾肥的响应存在显著差异,干旱胁迫下施钾使叶片水分利用效率(WUE)增大,气孔导度(Gs)降低,气孔阻力增大,蒸腾速率(Tr)和胞间CO2浓度(Ci)降低,水分蒸腾量减少; 而正常灌水条件下上述指标对钾肥的响应趋势相反。两种水分条件下施钾均可以增大叶片相对含水量(RWC),提高实际光化学效率(ΦPSII)和最大光化学效率(Fv/Fm),但是干旱胁迫下施钾增幅较大。【结论】干旱胁迫下适量施钾可以提高甘薯的抗旱性,增加甘薯产量,过量施钾使甘薯产量显著降低,而正常水分供应时,稍多钾肥对产量影响不显著。干旱胁迫与正常灌水条件下施钾对叶片光合参数的调控效应存在显著差异。施用钾肥可增大叶面积,提高叶绿素含量和光合性能,调节叶片气孔关闭,增大叶片气孔阻力,减少水分蒸腾损失,增加叶片相对含水量,提高水分利用效率和净光合速率; 施钾还能提高叶片PSⅡ原初光能转换效率和实际光化学效率,减少过剩激发能对光合机构的破坏,提高甘薯叶片的光合能力。干旱条件下钾肥的调节功能优于正常水肥供应。     

Effects of Sodium on Potassium Nutrition in Three Tropical Root Crop Species

The potassium (K) nutrition and high K requirement of tropical root crops may be affected by their sodium (Na) status, as has been observed in a number of plant species. Solution culture was used to study the effects of K and Na supplies in tannia [Xanthosoma sagittifolium (L.) Schott.], sweet potato [Ipomoea batatas (L.) Lam.] and taro [Colocasia esculenta (L.) Schott]. At low K supply, Na ameliorated symptoms of K deficiency and increased growth in tannia, and to a lesser extent in sweet potato, but not in taro. None of the species responded to Na at adequate K supply. Differences in response to Na were attributed to differences in Na translocation to plant tops. At maximum Na supply, the Na concentration in index leaves averaged 1.82% in tannia, 0.205% in sweet potato, and 0.0067% in taro. An increase in the supply of Na resulted in a shift in the critical K concentration for deficiency (i.e., 90% of maximum yield) in index leaves from 2.9% to 1.2% in tannia, and from 4.8% to 2.5% in sweet potato. The critical K concentration in taro was 3.3%, irrespective of Na supply. To overcome the problem in tannia and sweet potato of determining the critical concentration relevant to a leaf sample of unknown K status, a relationship was established for each species relating the critical K concentration to the concentration of Na in the index leaves.     

磷对淀粉型甘薯产量及养分吸收利用的影响

【目的】研究不同磷肥用量对甘薯养分吸收、分配及产量的影响,探究淀粉型甘薯磷肥营养效应,为甘薯高产科学合理施用磷肥提供理论依据。【方法】以淀粉型甘薯渝薯17(淀粉含量24.06%)为材料,设置7个磷肥处理(P2O50、0、37.5、75、112.5、150、300 kg/hm2),田间随机区组排列。其P2O50处理不施任何肥料,其他处理均底施纯氮(N)90 kg/hm2和K2O 150 kg/hm2。甘薯苗移栽后每隔30 d,共计取样5次,对全株样品分叶片、茎蔓和块根测定其鲜重、干重及全氮、磷、钾的含量。收获期测定小区鲜薯产量、茎蔓产量并计算收获指数(HI)及其磷肥农学效率(PAE)、磷肥表观利用率(PAUE)、磷收获指数(PHI)、磷肥生理利用率(PPUE)、磷肥偏生产力(PFPP)和磷肥增产率(PIR);同时计算收获期各器官N、P、K的吸收量,对N、P、K吸收量之间及其与产量之间关系进行相关性分析。【结果】1)适当增施磷肥有利于提高甘薯的经济产量、生物产量和收获指数,且以施P2O5112.5 kg/hm2和150kg/hm2时最优,经济产量增产率分别为19.4%和21.06%。2)不同器官N、P、K最高含量分别出现在栽后60、90、150 d,各处理氮素和磷素含量均为叶片茎蔓块根,而钾素含量为茎蔓叶片块根。栽后60 d后,叶片∶茎蔓∶块根含氮量为4.08∶1.62∶1,栽后90 d后,叶片∶茎蔓∶块根磷含量为2∶1.35∶1,栽后150 d后,茎蔓∶叶片∶块根含钾量为2∶1.8∶1。3)施磷可提高甘薯块根、茎蔓和叶片对N、P、K的吸收,养分总吸收量为钾氮磷;施磷处理中N、P、K的吸收量增幅分别为23.9%66.6%、29.6%58.5%、41.3%73.7%。磷钾吸收量均表现为块根茎蔓叶片,吸氮量表现为块根叶片茎蔓。4)在不同施磷条件下,形成500 kg所吸收的N、P2O5、K2O分别为4.24 6.61 g,1.93 2.84 g和6.94 11.48 g。施P2O5112.5 kg/hm2时,形成500 kg鲜薯吸收的养分最多,N、P2O5、K2O吸收量分别为6.61、2.84和11.08 g。5)磷肥表观利用率、偏生产力在施P2O537.5 kg/hm2时最高,分别为16.6%和343.0 kg/kg P2O5,磷肥农学效率、磷肥生理利用率和磷收获指数在施P2O5112.5 kg/hm2时最高,分别为136.7 kg/kg、777.9 kg/kg和65.9%。6)收获期各器官N、P、K吸收量之间及其与产量之间均呈显著或极显著正相关。【结论】增施磷肥能提高甘薯产量,但其利用效率有下降趋势。本试验中,从甘薯高产高效生产的磷肥管理角度分析,N和K2O施用量分别为90 kg/hm2和150 kg/hm2时,以施P2O5为112.5 kg/hm2为最佳。     

Antioxidant activities of trypsin inhibitor, a 33 KDa root storage protein of sweet potato (Ipomoea batatas (L.) Lam cv. Tainong 57).

Trypsin inhibitors (TIs), root storage proteins, were purified from sweet potato (Ipomoea batatas[L.] Lam cv. Tainong 57) roots by trypsin affinity column according to the methods of Hou and Lin (Plant Sci. 1997, 126, 11-19 and Plant Sci. 1997, 128, 151-158). A single band of 33 kDa TI was obtained by preparative sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) gels. This purified 33 kDa TI had scavenging activity against 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical. There was positive correlation between scavenging effects against DPPH (2 to 22%) and amounts of 33 kDa TI (1.92 to 46 pmol). The scavenging activities of 33 kDa TI against DPPH were calculated from linear regression to be about one-third of those of glutathione between 5 and 80 pmol. Using electron paramagnetic resonance (EPR) spectrometry for hydroxyl radical detection, it was found that 33 kDa TI could capture hydroxyl radical, and the intensities of EPR signal were significantly decreased from 1.5 to 6 pmol of 33 kDa TI compared to those of the controls. It is suggested that 33 kDa TI, one of the sweet potato root storage proteins, may play a role as an antioxidant in roots and may be beneficial to health when it is consumed.     

钾肥基施利于甘薯块根产量的形成

【目的】 研究不同施钾方法对甘薯块根产量形成的影响,可为甘薯高产稳产寻找合理的钾肥施用方法,并阐明其增产机理。【方法】 选取典型的食用型甘薯品种红香蕉和北京553为试材,于2013~2014年两个生长季在山东农业大学农学试验站进行田间试验。设4个施钾处理:不施钾肥（CK）、全部钾肥基施（JS）、全部钾肥封垄期追施（FS）、基施钾肥和封垄期追施钾肥各占50%（1/₂ JS+1/₂ FS）。在主茎第4、5片展开叶上标记13CO₂,24、48和96 h后取样,用质谱仪（Isoprime 100）测定不同部位的13C含量。从甘薯栽秧后50 d开始,每隔20 d取样直到收获。按根、茎、叶、柄四部分分别称重,将主茎自功能叶所在位置至基部等分为三段,取上、下两端用于测定蔗糖含量。收获期测定生物产量和块根产量,计算经济系数。【结果】 甘薯施用钾肥能显著提高生物产量、经济系数和块根产量,增产21.33%~34.38%。各施钾处理之间比较,生物产量差异不显著,经济系数和块根产量差异显著,其中基施钾肥处理的经济系数和块根产量最高。栽秧后50 d,基施钾肥处理植株干物质积累量和功能叶光合产物在块根中的分配率都显著高于其他施钾处理。栽秧后50 d和110 d,基施钾肥处理光合产物源端装载和库端卸载的效率显著高于其他处理,栽秧后150 d,所有施钾肥处理趋于一致。栽秧后50 d,基施钾肥处理光合产物转运效率显著高于其他施钾处理,栽秧后100 d和150 d,施钾肥处理间效果趋于一致。在栽秧后50~130 d,基施钾肥处理的块根膨大速率一直高于其他施钾处理。【结论】 在相同供试土壤和气候条件下,钾肥施用时间越早,越有利于甘薯早发、快长,促进块根早形成、快膨大;光合产物由叶片向块根运转效率的高值持续期越长,越有利于提高光合产物在块根中的分配。因此,全部钾肥基施甘薯经济系数和块根产量最高,是最经济有效的施肥方法。     

不同类型甘薯品种氮、 钾积累分配及其与产量性状的关系

试验对6个不同类型甘薯品种的氮、钾积累动态、地上部与地下部氮、钾的分配差异进行了系统研究,同时分析了氮、钾含量与产量性状的关系。结果表明,不同甘薯品种藤蔓的氮含量自块根形成后逐渐下降,其干物质氮含量仅为2%左右,而块根氮含量在整个块根膨大期间变化较小,且前、后期含量基本一致。藤蔓和块根钾含量在块根膨大期间也相对稳定。藤蔓氮含量极显著高于块根氮含量;藤蔓与块根中的钾含量则相反。在不同类型甘薯之间,高淀粉类型（HS）品种块根干物质氮含量在0.68%～0.86%之间,藤蔓氮含量在1.98%～3.32%之间,低淀粉类型（LS）品种块根与藤蔓氮含量分别在0.69%～0.86%和2.00%～3.17%之间,但无论是藤蔓还是块根,氮含量在不同类型品种间无显著差异;高淀粉类型品种的块根钾含量为5.83%～6.66%,藤蔓钾含量为3.19%～3.70%,而低淀粉类型品种的块根与藤蔓钾含量分别为6.12%～6.36%与3.48%～3.90%。相关分析表明,对所有品种来说,块根的钾含量与其氮含量之间呈显著正相关,藤蔓的钾含量与根冠钾含量之比也达到了显著负相关;就高淀粉类型品种而言,藤蔓氮含量与干率之间、根冠钾含量之比与商品薯率之间均为极显著正相关,块根钾含量与生物产量呈显著负相关;低淀粉类型品种的藤蔓氮含量与生物产量呈显著正相关关系,藤蔓钾含量与生物产量、淀粉产量分别呈极显著正相关和显著负相关关系。     

不同基因型甘薯（Ipomoea batatas Lam.）吸收累积Cd的特征差异性研究

采用旱地小区试验,研究了Cd污染土壤中甘薯吸收累积Cd的品种差异,探讨了甘薯吸收累积Cd的相关机理。结果表明,甘薯品种间不仅生物量差异较大,对Cd的吸收累积能力也不同,8个品种的地上部茎叶生物量（DW）在4 594.9-8 232.2 kg.hm^-2,鲜样Cd含量范围为0.032 9-0.057 4 mg.kg^-1;地下部块根生物量（DW）在7 809.0-14 269.7 kg.hm^-2,鲜样Cd含量范围为0.002 2-0.011 0 mg.kg^-1,茎叶Cd含量明显高于块根,但均未超过国家食品中污染物限值标准（GB 2762—2005）（根茎类蔬菜〈0.1 mg.kg^-1）。而与无公害蔬菜质量标准（GB 18406.1—2001）进行比较（〈0.05 mg.kg-1）,有3个甘薯品种（心香、湘薯15、泉薯9号）的茎叶Cd含量超标。因此,轻度Cd污染土壤种植的甘薯其茎叶可能存在摄食健康风险,而块根基本无风险,若将Cd污染土壤改制种植甘薯,必须妥善处理其地上部茎叶。     

氮肥用量对滨海滩涂区甘薯干物质积累、氮素效率和钾钠吸收的影响

我国沿海滩涂种植能源作物甘薯有广阔的前景。为确定苏北滩涂区甘薯适宜施氮量,比较了6个施氮水平下甘薯的成活率(SR)、商品率(CR)、蔓薯比(V/T)、干物质积累(DMA)、氮素累积值(NAV)、氮利用效率(NUE)、氮收获指数(NHI)及钾钠吸收的差异。结果表明:(1)施氮量与甘薯地上部分DMA和NAV均呈极显著正相关(P<0.01,余同),对地下部分NAV影响较小(P>0.05)。(2)与不施氮比较,施氮60 kg(N)·hm-2对甘薯的V/T、SR、NUE和NHI均无显著影响。(3)甘薯的CR、地下部分和块根DMA以及理论产量(NAV×NUE×NHI)均以施氮60 kg(N)·hm-2显著高于其他处理。施氮量超过60 kg(N)·hm-2,施氮量与甘薯的V/T值呈极显著正相关,与SR、CR、NUE、NHI、地下部分和块根DMA均呈极显著负相关。(4)甘薯对钾钠的吸收量均随施氮量的增加而增加,二者呈极显著正相关。甘薯地上部分钾钠含量均在施氮量为60 kg(N)·hm-2时达到最高值。施氮量对钾钠含量比没有影响。因此,苏北滩涂区甘薯适宜施氮量为60 kg(N)·hm-2。