Gibberellins and tuberization in potato

Summary The evidence for a role of gibberellins in the regulation of potato tuber formation is reviewed. Endogenous gibberellin levels in plants are high under non-inducing conditions and decrease under inducing conditions. Exogenously applied gibberellins inhibit tuber formation, whereas applying inhibitors of gibberellin biosynthesis has the opposite effect. Cellular events involved in tuberization, viz., cell division, cell enlargement and orientation of micro-tubules, are also reviewed. Based on available evidence, a major regulatory role of gibberellins is suggested. However, it is also argued that tuber formation is not simply regulated by gibberellins acting as the sole signal between above-ground and below-ground parts, since stolon tips are able to synthesize their own gibberellins, and the phenotype of phytochrome B-antisense plants cannot be explained only by altered levels of GAs.     

赤霉素和脱落酸对马铃薯块茎形成的影响

研究结果表明,马铃薯块茎形成期,脱落酸含量显著增加,赤霉素含量则显著降低,赤霉素与脱落酸比值下降到一定水平是块茎开始形成的重要条件.外加脱落酸喷施叶面,使块茎形成提早,但结薯数并未增加;外加赤霉素喷施叶面,使植株细高,匍匐茎细长,块茎形成显著延迟,块茎数显著减少,这一结果进一步证明了脱落酸和赤霉素在块茎形成中的作用.     

Invertase activity as affected by cytokinin-like compounds during potato tuberizationin vitro

Acid invertase plays an important role in plants by hydrolyzing sucrose. Compounds exhibiting cytokinin activity were examined for their effects on acid invertase activity at three tuberization stages of potato,Solanum tuberosum L. Single nodal segments from the cultivar Atlantic were cultured on Murashige and Skoog (MS) medium with 6% sucrose and maintained under a 16-hr photoperiod. Media were supplemented with either 2 mg kinetin/1, 0.1 mg thidiazuron/1,1.0 mg AC243, 654/1 (a benzyl nitroguanidine), or 0.1 mg AC239, 604/1 (a phenyl nitroguanidine). Basal acid invertase activity was measured in stolon segments at three morphologically distinct tuberization stages: (1) “hook,” (2) “swelling,” and (3) “initiation.” The onset of tuber initiation was significantly advanced by kinetin and thidiazuron compared to controls. Stolons elongated during the hook and swelling stages until tubers were initiated. Basal acid invertase activity in stolons cultured on control medium significantly increased from hook stage to swelling stage and then decreased slightly when tubers were initiated. At the hook stage, highest basal acid invertase activity occurred when the segments were treated with kinetin and thidiazuron. Kinetin and thidiazuron induced basal acid invertase activity significantly decreased following the hook stage to tuber initiation. Basal acid invertase activity were significantly lower in stolons treated with nitroguanidines than the control activity following the hook stage of development. During the swelling and tuber initiation stages, nitroguanidines-treated segments showed reduction in basal acid invertase activity similar to segments treated with kinetin and thidiazuron treatments. Tuber initiation was preceded by a stimulation of basal acid invertase activity followed by a decrease prior to tuber initiation. Kinetin and thidiazuron stimulated enzyme activity early in the growth of stolons which may have resulted in faster stolon growth and in earlier tuber initiation. The two nitroguanidines, although able to mimic many cytokinin effects in bioassays, did not seem to act in the same way as kinetin.     

The effect of simazine and cytokinins on potato tuber protein,nitrogen content and yield1,2

Summary Experiments were conducted on potted potato plants to evaluate the potential of simazine and cytokinins to increase tuber protein content. Foliar sprays with higher concentrations of simazine (2 to 4 mg per litre) decreased yield. Repeated applications during tuber development tended to increase tuber nitrogen content; however, large increases in nitrogen were difficult to reproduce. Weekly applications of simazine (150 ml of 0.025 to 0.2μM) to the soil during tuberization and tuber development did not increase tuber nitrogen or protein, but tended to increase yields. A single soil application of SD 8339³, kinetin or benzyladenine did not increase tuber nitrogen or protein. These methods of simazine and cytokinin application do not appear practical as a means of increasing potato tuber protein content. This research was supported in part by a grant from the Rockefeller Founcation. Scientific Journal Series Article 8665 of the Minnesota Agricultural Experiment Station.     

Tuberization in potato at high temperatures: Responses to exogenous gibberellin,cytokinin and ethylene

Summary In potato (Solanum tuberosum L., cv. Sebago), benzyladenine (BA) promoted tuberization at high day/night temperatures (32°/18°C), while gibberrellic acid (GA) and chlorethylphosphonic acid (CEPA) reduced tuberization at low day/night temperatures (22°/18°C). These results are consistent with the hypothesis that temperature exerts its influence on tuber formation by altering the balance between endogenous gibberellins, cytokinins and inhibitors, but not ethylene.     

Possible mechanisms of size hierarchy among tubers on one stem of a potato (Solanum tuberosum L.) plant

Summary The tubers on one potato stem vary greatly in size and their size distribution may be described by their number and their average size and its variation. These components are mutually and closely related. The variation is partly caused by stolon characteristics, including their date of initiation, position and size. Tuber size is therefore partly determined before tuberization. Tuber-specific factors, such as the position and activity of the tuber initial also play a role, but the date of initiation of an individual tuber is not crucial. Later on, during tuber bulking, the activity of enzymes involved in starch metabolism, the levels of hormones, the mineral composition and the turgor potential are associated with the tuber growth rate. The growth characteristics of individual tubers may also vary since they are exposed to different conditions because of differences in position or growing period.     

Effects of exogenous applications of cytokinin on the development of potato (Solanum tuberosum L.) cuttings

Summary Application of 6-benzylaminopurine or its riboside to potato cuttings on four successive days was very effective if the treatment started on day 4 after cutting. These cytokinis caused cuttings that were well induced to express a lower level of induction than they actually had received. There was a shift from sessile tuberization of the central bud to non-sessile tuberization of the central bud or to tuberization of ancillary buds, or a shift from ancillary-bud tuberization to swollen shoots. Effects were largest after a moderate induction. If rooting occurred, cytokinin reduced the proportion of rooted cuttings significantly. Cytokinin increased the levels of fructose and glucose in the tubers if it was applied after day 3. Dry weight of the buds was reduced by cytokinin in those cases where it caused suppression of ancillary-bud development. Paper No 836, Department of Vegetable Crops, Cornell University, Ithaca, N.Y. 14853, USA.     

Effects of photoperiod on kinetin-induced tuberization of isolated potato stolons culturedin vitro

Are short-day (SD) conditions inductive or permissive for potato tuberization? This question was addressed using anin vitro culture system. Kinetin induction ofin vitro tuberization in potato stolons cultured in the dark can be partially inhibited by light treatments. Photoperiod required for a major inhibition varied with cultivars: 8 hours for cv. Red Pontiac and 16 hours for cv. Kennebec. Short photoperiods decreased kinetininduced tuberization for all cultivars. Stolons cultured on kinetin-free medium generally did not tuberize, regardless of light treatment. Effects of kinetin and photoperiod on stolon and tuber development are observed. Relationships among kinetin, photoperiod and tuber-inducing stimulus produced under short days are discussed.     

温度影响马铃薯块茎形成的研究进展

块茎是马铃薯的商品和营养繁殖器官,而温度是影响块茎形成最重要的环境因素之一.针对温度对马铃薯块茎诱导和起始、膨大和成熟生长发育阶段表型变化的影响,对光合特性、源库平衡和渗透调节物质等生理生化变化影响,对调控块茎形成的光周期、植物激素、sRNA和糖类物质通路的影响,以及马铃薯耐热性评价和遗传改良研究等方面进行了综述,以期...     

Utilization of potatoes for life support systems II. The effects of temperature under 24-H and 12-H photoperiods

The growth and tuberization of Norland potatoes were studied under five different temperatures and two photoperiods. Treatment levels included 12, 16, 20, 24, and 28 C with either a 24-h (continuous light) or a 12-h photoperiod at 400 μmol m^-2 s^-1 PPF. Plants were grown in 6-liter containers and harvested at 56-days-age. Stem length increased with increasing temperature under both photoperiods. The highest tuber yield occurred at 16 C under the 24-h photoperiod (755 g/plant) and at 20 C under the 12-h photoperiod (460 g/plant). Little or no tuber formation occurred at 28 C under either photoperiod or at 24 C under continuous light. As with tuber yield, the highest total plant dry weights also occurred at 16 C under the 24-h photoperiod and at 20 C under the 12-h photoperiod. Harvest index (tuber dry weight to total dry weight ratio) decreased with increasing temperatures and with continuous light. Results indicate that good growth and tuberization can occur under continuous light, and that increasing the photoperiod from 12 to 24 h effectively decreased the optimal temperature for tuber formation from near 20 C to 16 C. Alternatively, the results imply that at cooler temperatures, the potato becomes less obligate for dark period stimulation of tuberization.     

Comparison of the protein in axillary bud tubers and underground stolon tubers in potato

To determine if axillary leaf bud tubers can be used to study tuber protein synthesis in potato we have compared the proteins in axillary bud tubers with those in underground stolon tubers in the variety Superior. By SDS polyacrylamide gel electrophoresis and by electrophoresis in nondenaturing polyacrylamide gels at pH 8.6, the proteins in axillary bud tubers appear to be the same as those in underground stolon tubers. The proteins also appear to be immunologically identical based on Ouchterlony double immunodiffusion test and immunoelectrophoresis.     

Anatomy and compositional variation within potatoes

Re-examination of the histological development of the potato tuber supports Artschwager’s view that tuber growth is predominantly due to enlargement of the perimedullary zone and is of procambial origin. Pith (medulla) and cortical regions are differentiated from the ground or fundamental meristem derived from the apical meristem of the stolon apex, even before tuberization has been initiated. The procambium gives rise to external phloem, primary xylem, internal phloem and associated parenchyma, and likewise to interfascicular parenchyma. Those parenchyma cells so formed inwardly to the xylem “ring” contribute to the growth of the perimedullary zone. The sequence of tissue origins is diagrammed and discussed from the viewpoint of modern concepts of histogenesis.     

高温下马铃薯试管薯的诱导

对金冠、大西洋、会顺 88等 3个品种进行了高温下、短日照 (8h/d)添加不同浓度BA和蔗糖的切段诱导结薯。结果显示 ,高温抑制了 3个品种的结薯 ,特别对大西洋抑制最强。高温下加入不同浓度的BA对 3个品种产生不一致的影响。高温下蔗糖浓度为 2 % ,不加激素时 ,对这 3个品种不能诱导其结薯     

Manipulating Aeroponically Grown Potatoes with Gibberellins and Calcium Nitrate

Maximizing tuber number and yield in an aeroponics production system is imperative to make it cost effective and to make the best use of all facilities and inputs. Manipulating the plants hormonal makeup is a strategy. GA3(GA), Calcium Nitrate(CaN) and their combination were foliarly applied several times to potato plants of cvs. Favorita and Mira during both the autumn and spring growing seasons in a semi tropical setting in Sichuan. A contrasting treatment of an anti-gibberellin(Anti) was also studied in both seasons. Significant differences in plants height, stem diameter, chlorophyll content, leaf area index, the number of stolons, the number of stolon branches and tuber production were observed among different treatments and cultivars. For the cv. Favorita, CaN?+?GA and GA increased tuber weight per plant by 63 and 49% in autumn and 53 and 73% in spring respectively as compared to the control(CK); tuber number per plant under CaN?+?GA and GA treatments increased by 90 and 85% in autumn and 35 and 52% in spring respectively. For cv. Mira, the trend was similar but not as dramatic. Tuber numbers over 1400 per square meter were harvested with cv. Mira during the spring season with the GA and CaN?+?GA treatments.     

不同生长调节剂对马铃薯微型薯结薯的影响

采用烯效唑、B9、水杨酸处理种植在大棚基质中的大西洋脱毒试管苗,比较不同生长调节剂对马铃薯微型薯结薯的影响。结果表明:烯效唑对植株的生长有促进效果,以100 mg.L-1处理具有最佳效果,随着浓度的增加,处理出现的负效果越大;B9喷施的植株单块茎重和总块茎重均以2 500 mg.L-1浓度的处理最高,且大、中大薯在总块茎数所占的比例最大;水杨酸以400 mg.L-1浓度的处理效果最好。     

Hydroxylated jasmonate levels during stolon to tuber transition inSolarium tuberosum L

Summary Various octadecanoids and derived compounds have been identified in potato leaves. However, information regarding jasmonate hydroxylated forms in stolons or tubers is scarce. We investigated endogenous jasmonates in stolon material ofSolarium tuberosum cv. Spunta. Stolons and incipient tubers were collected from 8 weeks old plants. The material was cut into apical regions and stolons. We identified jasmonic acid (JA), methyl jasmonate, 11-OH-JA, 12-OH-JA, 12-oxo-phytodienoic acid (OPDA) and a conjugate. The content of JA and 12OH-JA decreased in the apical region but remained high in stolons during tuberization. Thus the apical region might be a site of JAs-utilization or metabolization and stolons might supply JAs to that region. The content of 12-OH-JA was higher than that of 11-OH-JA in all stages analyzed, both in apical regions and stolons. However, these compounds showed a different time-course in the apical region: while 11-OH-JA increased, 12-OH-JA decreased. Thus, JA from leaves or roots could be transported as 12-OH-JA to the apical region, stimulating tuber formation.     

Is dormancy breaking of potato tubers the reverse of tuber initiation?

Summary Tuber formation is a well orchestrated physiological event that involves many metabolic changes. Dormancy gradually develops in potato tubers from the moment cell division in the stolon tip has stopped and the tuber starts to develop. Dormancy breakage may be the reverse of dormancy initiation suggesting that there may be similarities between tuber induction and dormancy development. Based on a literature review it is concluded that, when comparing tuber induction and the breaking of dormancy, hormonal activities are only partly reversed, whereas carbohydrates and enzyme activities might be reversed. For more definite conclusions more research should be done to assess precisely the moment of dormancy breaking. Moreover, measurements on events associated with tuber induction and dormancy breaking should be carried out using the same techniques and the same material. Molecular genetic analyses may provide well-defined markers for the timing of breaking of dormancy.     

马铃薯匍匐茎与块茎建成规律的研究

马铃薯匍匐茎及块茎的建成与光合系统状况及干物质分配密切相关。匍匐茎形成与地上茎生长间存在对光合产物的竞争 ,光合系统的迅速建成有利于匍匐茎和块茎的发生 ;虽然植株的干物质大量分配到匍匐茎和块茎 ,有利于二者的建成 ,但其建成仍然以地上部各器官的建成为物质基础。     

马铃薯休眠块茎上芽眼组织休眠机理研究

以早熟品种中薯 3号和加工品种大西洋脱毒试管薯为试验材料 ,通过对休眠块茎芽薯分离培养 ,研究休眠块茎上芽离体培养后的生长发育变化。初步结果表明 ,休眠马铃薯块茎上侧芽停止生长始于匍匐茎生长期 ,主要受顶端优势的影响 ;顶芽停止生长开始于块茎形成起始 ,可能是因为匍匐茎上的细胞分裂中心和代谢重心转移影响 ;在块茎休眠过程中顶芽和侧芽不生长主要是受到来自块茎内部因素的抑制 ;当芽从休眠块茎上分离出来 ,在培养基上能够很快的生长。马铃薯块茎休眠和块茎上芽的休眠可能是两种不同的生理机制所控制。     

The effect of the inhibitors of protein and nucleic acid synthesis on the coumarin-induced tuberization and growth of excised axillary shoots of potato sprquts (Solanum tuberosum l.) culturedin vitro

The inhibitors of protein and nucleic acid synthesis; chloramphenicol, para-fluorophenylalanine, actinomycin D, and 5-fluorouracil were evaluated for their effectiveness in inhibiting coumarin-induced tuberization, tuber growth, and the inhibition of.root and shoot growth of excised axillary shoots of potato sprouts culturedin vitro. To date, it has been demonstrated that both kinetin and coumarin readily effect 100 percent tuberization of the shoots culturedin vitro. The results of the present study demonstrate that with the exception of 5-fluorouracil, the inhibitors significantly inhibited the coumarin-induced. tuberization, tuber growth, and root growth whereas in previously published data by Palmer and Smith (6), the inhibitors merely delayed kinetin-induced tuberization. It is suggested that both protein and nucleic acid synthesis are required for the coumarin-induced tuberization processes, and the mode of action of coumarin is distinctly different from that of kinetin.