The position and growth of lateral roots on cultured root axes of tomato,Lycopersicon esculentum (Solanaceae)

Root axes of tomato (Lycopersicon esculentum) were cultured in vitro in three different concentrations of sucrose in order to vary their growth rate. Lateral root growth and the initiation of lateral root primordia were studied on each group of axes. Various aspects of primordium initiation, positioning, and emergence were quantified with a view to discovering variable and constant features of these processes. Variable parameters were the rate and frequency of root primordium emergence. Constant parameters, at least under the prevailing conditions, were the spacing between successive laterals and primordia, and the position of the primordia in relation to the vascular system. A model of primordium initiation is presented which combines controls determined by the divisional history of the potential primordium cell and by the vascular pattern.Dedicated with great respect to Prof. DrElisabeth Tschermak-Woess on the occasion of her 70th birthday in recognition of her distinguished contributions to cytology.     

Interactive effects of cadmium and aluminum on growth and antioxidative enzymes in soybean

The effects of Al, Cd and pH on growth, photosynthesis, malondialdehyde (MDA) content, and some antioxidant enzyme activities of the two soybean cultivars with different Al tolerance were determined using a hydroponic culture. There were six treatments as follows: pH 6.5; pH 4.0; pH 6.5 + 1.0 μM Cd; pH 4.0 + 1.0 μM Cd; pH 4.0 + 150 μM Al; pH 4.0 + 1.0 μM Cd + 150 μM Al. The results showed that the low pH (4.0) and Al treatments caused marked reduction in the growth (root and shoot length and dry mass), chlorophyll content (SPAD value) and net photosynthetic rate. Higher malondialdehyde content, superoxide dismutase (SOD) and peroxidase (POD) activities were detected in the plants exposed to both Al and Cd than in those exposed to Al treatment alone. An expressive enhancement of SOD and POD was observed in the plants exposed to 150 μM Al in the comparison with the control plants, especially in Al-sensitive cv. Zhechun 2 which had also significantly higher Al and Cd content than Al tolerant cv. Liao-1. Cd addition increased Al content in the plants exposed to Al + Cd stress, and cv. Zhechun 2 had relatively lower Al content. The present research indicated that Al and Cd are synergistic in their effects on plant growth and some physiological traits.     

镉胁迫对姬松茸生长和镉吸收累积的影响

利用外源镉添加的袋栽试验,系统研究了镉对姬松茸J37和J1两菌株农艺性状、子实体产量、氨基酸和镉含量的影响,以求为低富集镉的姬松茸品种选育和安全栽培提供科学依据。结果表明外源镉添加对姬松茸J37和J1品种子实体的农艺性状的影响各异,两菌株单个子实体重量、子实体高度、菌盖直径、菌盖厚度和菌柄直径等均与外源镉浓度具有显著的负相关性,其中子实体重量与外源镉浓度间的相关性最大;15 mg/kg镉水平是两菌株农艺性状发生显著变化的敏感点。不同镉水平下J37菌株单个子实体重量比J1菌株高10.9%—36.6%,表现为较强镉耐受性。姬松茸J37与J1菌株子实体产量、氨基酸和镉含量均随着潮次的增加而降低,子实体产量和氨基酸含量随着外源镉水平增加而降低,而镉含量随外源镉水平增加而增加。与外源镉0mg/kg处理相比,当外源镉水平达15 mg/kg时,J1和J37子实体总产量分别下降23.4%和13.4%以上,J1和J37子实体镉含量分别提高51.5%、13.7%以上,且J1子实体镉含量已达到食品卫生标准的临界值。当外源镉水平达到35 mg/kg时,J1和J37子实体产量分别下降45%、32%以上,J1和J...     

Comparison of the response to aluminum toxicity in gametophyte and sporophyte of four tomato (Lycopersicon esculentum Mill.) cultivars

Summary We tested pollen from four tomato cultivars differing in sensitivity to aluminum in the sporophyte to determine if Al sensitivity was also expressed in pollen. Pollen sensitivity to Al was measured by the ability to germinate and grow in a control solution after a short period in a high concentration of Al. The response was ranked and compared to the Al sensitivity ranking of the four cultivars based on top growth in Al toxic soil. In addition, seedlings from the most and least sensitive cultivars, based on pollen germination, were compared for Al sensitivity in nutrient solutions. Treatment with Al significantly reduced pollen germination in the two more sensitive cultivars, but not in the two more resistant cultivars. However, the ranking was not the same as that based on the shoot growth of the sporophyte. Root growth as a criterion of sporophytic Al sensitivity produced results similar to pollen germination. The study suggests that although the correspondence is better for some phenotypic responses of the sporophyte than others, Al tolerance appears to be another character expressed in both pollen and sporophyte.     

Glutathione reduces the inhibition of rice seedling root growth caused by cadmium

We investigated the effects of agents known to affect cellular glutathione (reduced form, GSH) levels on the growth of rice seedlings treated with Cd. CdCl₂ was more effective than CdSO₄ in inhibiting root growth. However, CdCl₂ had no effect on shoot growth. GSH, a substrate for phytochelatin synthesis, was effective in counteracting growth inhibition of roots by CdCl₂. Root growth in the CdCl₂ medium was found also to be enhanced by the addition of L-glutamic acid and L-cysteine, both of which are substrates for GSH formation. Buthionine sulfoximine, an inhibitor of GSH synthesis, rendered the roots susceptible to growth inhibition by Cd. Our results suggest that GSH level may play a role in regulating Cd-inhibited growth of rice roots.Abbreviations BSO buthionine sulfoximine - GSH reduced form glutathione     

镉胁迫对瘤突苍耳、苍耳及其杂合体种子萌发与幼苗生长的影响

入侵种与本地种杂交可能会改变其某些性状,影响其生理生化过程,增强其对一些重金属的耐受性。镉是目前造成土壤污染的主要重金属元素之一,为探讨杂交是否能够增强植物对重金属镉的耐受性,采用培养皿滤纸法比较了不同浓度镉(0,10,40,80和120 mg/L)处理下瘤突苍耳(Xanthium strumarium)、苍耳(Xanthium sibiricum)及二者杂合体(X.strumarium♀×X.sibiricum♂,X.sibiricum♀×X.strumarium♂)种子萌发与幼苗生长情况。结果表明:1)入侵种瘤突苍耳与本地种苍耳之间存在杂交现象;2)镉促进了杂交瘤突苍耳(X.strumarium♀×X.sibiricum♂)种子的萌发,当镉浓度为80 mg/L时,其萌发率、发芽势、发芽指数最高;3)杂交瘤突苍耳在80、120 mg/L镉处理下根长和叶绿素含量低于瘤突苍耳,但子叶受到的氧化胁迫并未高于瘤突苍耳。研究结果显示,杂交有可能提高了瘤突苍耳在高浓度镉胁迫时对重金属镉的转运能力,幼苗根系吸收大量的镉并向上运输给子叶,导致根系生长受到抑制、子叶叶绿素含量下降,抗氧化酶系统可能在降...     

秋华柳和枫杨幼苗对镉的积累和耐受性

以秋华柳和枫杨当年实生幼苗为研究对象,采用向土壤添加外源镉(CdCl₂ · 2.5H₂O)的形式设置了0(对照组)、10 、20 、50、100 mg/kg 5个处理,研究了镉胁迫下秋华柳和枫杨幼苗的生长、生物量变化和根茎叶镉含量,并评价了两树种的耐性指数(Ti)、转移系数(Tf)和生物富集系数(BCF)。结果表明:(1)在镉含量为10 mg/kg时,秋华柳和枫杨幼苗基于生长和生物量参数的耐性指数(Ti)分别为91.72和91.62,与对照组相比无显著变化,其余各组(20、50、100 mg/kg)则显著低于对照植株(P<0.05);(2) 土壤镉浓度小于20mg/kg时,秋华柳植株茎、叶镉积累量分别高达61.73 mg/kg、163.04 mg/kg,根镉积累量为91.05 mg/kg;枫杨植株茎、叶镉积累量最高分别为7.9 mg/kg、5.25 mg/kg,仅为秋华柳茎、叶的12.8%和3.2%,根镉积累量高达190.68 mg/kg;(3) 除对照外,秋华柳幼苗各部分镉含量为叶＞根＞茎,转移系数(Tf)介于0.789-1.513之间,枫杨幼苗各部分镉含量为根＞茎＞叶,转移系数(Tf)介于0.037-0.044之间,远远小于秋华柳Tf;(4)秋华柳和枫杨幼苗在土壤镉浓度为10 mg/kg时具有很高的生长适应性和耐性,秋华柳根吸收的镉向地上部分转移能力、地上部分积累镉的能力都远远大于枫杨,生物富集系数(BCF)进一步证实了这一特性。研究证明,秋华柳植株具有很高的镉耐性、镉转移能力及地上部分积累镉的能力,适合于镉污染严重区域的植物修复。     

镉胁迫下植物促生菌密歇根克雷伯氏菌TS8和Lelliottia jeotgali MR2对拟南芥生长及镉富集的影响北大核心CSCD

为了研究镉胁迫下植物促生菌密歇根克雷伯氏菌(Klebsiella michiganensis)TS8和Lelliottia jeotgaliMR2对拟南芥(Arabidopsis thaliana)生长及镉富集的影响,文中以野生型拟南芥为试验材料,将其种植在不同镉浓度的土壤基质中,并施入MR2和TS8菌悬液。低浓度镉处理组(LC)为购买的基质营养土,初始镉浓度为14.17 mg/kg,高浓度处理组(HC)为在购买的基质营养土上额外喷洒200 mg/kg Cd^(2+)。结果表明,相比对照组,不同浓度镉胁迫下喷施MR2菌悬液均可显著促进拟南芥的生长,而TS8和MR2_TS8混合菌液仅在高浓度镉胁迫下表现出一定的促生效果。但值得关注的是,不同浓度镉胁迫下TS8菌悬液可显著降低拟南芥的地下部对重金属镉的富集(60%和59%),并有效提高地上部对重金属镉的富集(234%和35%)。此外,单菌和混合菌均能显著提高土壤中可还原态镉向酸可提取态镉转化,促进植物吸收,降低土壤总镉含量。因此,针对不同环境下,合理配施植物促生细菌在提高作物产量或修复土壤镉污染中具有一定的应用价值。     

The effect of cadmium on lipid and fatty acid biosynthesis in tomato leaves

This research aims to examine the effect of cadmium uptake on lipid composition and fatty acid biosynthesis, in young leaves of tomato treated seedlings (Lycopersicon esculentum cv. Ibiza F1). Results in membrane lipids investigations revealed that high cadmium concentrations affect the main lipid classes, leading to strong changes in their composition and fatty acid content. Thus, the exposure of tomato plants to cadmium caused a concentration-related decrease in the unsaturated fatty acid content, resulting in a lower degree of fatty acid unsaturation. The level of lipid peroxides was significantly enhanced at high Cd concentrations. Studies of the lipid metabolism using radioactive labelling with [1-¹⁴C]acetate as a major precursor of lipid biosynthesis, showed that levels of radioactivity incorporation in total lipids as well as in all lipid classes were lowered by Cd doses. In total lipid fatty acids, [1-¹⁴C]acetate incorporation was reduced in tri-unsaturated fatty acids (C16:3 and C18:3); While it was enhanced in the palmitic (C16:0), palmitoleic (C16:1), stearic (C18:0) and linoleic (C18:2) acids. [1-¹⁴C]acetate incorporation into C16:3 and C18:3 of galactolipids [monogalactosyldiacylglycerol (MGDG) and digalactosyldiacylglycerol (DGDG)] and some phospholipids [phosphatidylcholine (PC) and phosphatidylglycerol (PG)] was inhibited by Cd stress. Our results showed that in tomato plants, cadmium stress provoked an inhibition of polar lipid biosynthesis and reduced fatty acid desaturation process.     

Effect of lacZY-marking of the 2,4-diacetyl-phloroglucinol producing Pseudomonas fluorescens-strain 5-2/4 on its physiological performance and root colonization ability

Transgenic Pseudomonas fluorescens 5-2/4 with reinforced 2,4-diacetyl phloroglucinol (phl) production had shown increased biocontrol ability towards Pythium ultimum (Pu), but inferior root colonization ability compared to its wild type 5.014. Therefore, enhanced root colonization ability of the transgenic strain by repeated inoculation and reisolation on tomato plants was suggested. As a preparation for repeated inoculation and reisolation cycles, the construction of a negative control of the transgenic strain 5-2/4 by marking with lacZY and screening for a mutant possessing qualities comparable to 5-2/4 was performed. Morphologically, colonies of all of the 11 selected mutants were similar on MLXgal medium. The root colonization ability of two of the lacZY-marked strains (mutants 1 and 10) was comparable to the parental strain. These were also able to compete with the resident microflora of tomato seedlings to the same extent as the parental strain. Five mutants were excluded due to lower growth rates on Yeast Malt, King's B Medium (KB) and 0.1 Tryptic Soy Agar (mutant 4, 5 and 8), excessive growth and higher siderophore production on KB (mutant 10) and increased protease production (mutant 2). With respect to in vitro-antagonism of Pu, no differences could be found between the target strain and mutants 1, 3, 6, 7 and 9. Examination of sole carbon source utilization of these five lacZY-marked strains revealed a significantly higher utilization of alpha-D-lactose and lactulose compared to 5-2/4. However, significant differences could be found for 51% of the utilized carbon sources. Cluster analysis showed a high degree of similarity between 5-2/4 and mutant 1 both when analyzed with and without alpha-D-lactose. As mutant 1 also represented the colonization pattern most similar to the parental strain 5-2/4, it presents a presumptive subject for a negative control in the following inoculation and reisolation studies on tomato.     

Salt tolerance conferred by overexpression of Arabidopsis vacuolar Na+/H+ antiporter gene AtNHX1 in common buckwheat (Fagopyrum esculentum)

Agriculture productivity is severely affected by soil salinity. One possible mechanism by which plants could survive salt stress is to compartmentalize sodium ions away from the cytosol. In the present work, transgenic buckwheat plants overexpressing AtNHX1, a vacuolar Na⁺/H⁺ antiporter gene from Arabidopsis thaliana, were regenerated after transformation with Agrobacterium tumefaciens. These plants were able to grow, flower and accumulate more rutin in the presence of 200 mmol/l sodium chloride. Moreover, the content of important nutrients in buckwheat was not affected by the high salinity of the soil. These results demonstrated the potential value of these transgenic plants for agriculture use in saline soil.     

Reversibility of the effects of cadmium on the growth and nitrogen metabolism in the tomato(Lycopersicon esculentum)

In order to better understand the effects of heavy metals on the growth of plants, we decided to perform recovering experiments by following both chemical and physiological parameters in cadmium pre-stressed tomato seedlings after cadmium had been removed from the nutrient solution. The work shows that cadmium suppression results in resumption of growth activity. The biomass of leaves and stems rose steadily. The increase in root biomass exceeded those of leaves and stems. At the same time, nitrate content was increased to reach the level obtained with unstressed controls. In all the organs studied, the activities of the enzymes involved in the anabolic nitrogen primary assimilation pathways (nitrate reductase (NR), nitrite reductase (NiR) and glutamine synthetase (GS) soared after that cadmium had been removed. While NAD(+)-dependent glutamate dehydrogenase (GDH-NAD+) activity also rose progressively during the recovering time, the cognate NADH-dependent glutamate dehydrogenase (GDH-NADH) activity decreased. This result allows us to propose that the ammonia produced by the stress-induced protein catabolism is detoxified and re-assimilated by the GDH-NADH isoenzyme. On the basis of these results, we will discuss the ability of the plant to dilute the effects of pollutants during the recovering period. An important outcome of this work is that a transient contamination of the culture medium by pollutants is not necessarily followed by a significant depreciation in product yield or quality.     

Endophytic fungi in leaves of Lycopersicon esculentum Mill

Endophytic fungi were isolated from healthy tomato leaves from field-grown plants. Several surface-sterilization techniques were assayed for removing and killing epiphytes on tomato leaves. Surface-sterilization with an undiluted commercial solution of sodium hypochlorite was employed. To determine the spectrum of endophytes, samples were collected in February 1998 and 1999 from tomato plants (cultivar Tommy) cultivated in the experimental fields of Facultad de Ciencias Agrarias y Forestales, Universidad Nacional de La Plata, Buenos Aires, Argentina. In general, different spectra of species were isolated in 1998 and 1999.Alternaria alternata was the fungus most frequently isolated from tomato leaves in 1999, but it was the second most common species in 1998. In contrast, Colletotrichum gloeosporioides was the fungus most frequently isolated in 1998, but it was not found in 1999. Species of other genera, such as Cladosporium and Penicillium, were isolated in both years.     

一株虾池来源的螺旋拟柱孢藻藻株的分离鉴定及重金属离子Cu~(2+)、Cd~(2+)和Pb~(2+)对其生长的影响

【目的】探讨凡纳滨对虾养殖水体中入侵蓝藻拟柱孢藻的生长生理特性。【方法】从汕头澄海人工对虾养殖池分离纯化藻株,通过形态及其16SrRNA基因鉴定,之后在CT与BG11两种蓝藻通用培养基的基础上优化最佳培养条件,最后分析了不同浓度的3种重金属离子即Cu~(2+)(0–0.8 mg/L)、Cd~(2+)(0–4 mg/L)和Pb~(2+)(0–80 mg/L)对藻株生长的影响。【结果】澄海虾池来源的分离纯化藻株形态呈卷曲螺旋型,16S rRNA基因序列与多株其他来源的拟柱孢藻相似度均达98%以上。实验室培养,藻株最佳生长状态的培养条件是在BG11培养基的基础上调整氮浓度及氮磷比分别为N 62 mg/L,N︰P=9︰1,在此条件下,藻丝生物量可达(0.632±0.170)×107/L,藻丝比平均生长速率最高为(0.063±0.001)/d。本分离藻株活体对重金属Cu~(2+)、Cd~(2+)和Pb~(2+)具有一定的耐受性,其耐受浓度范围分别为0–0.2、0–0.5和1–40 mg/L,其中,Cu~(2+)和Cd~(2+)对藻的生长具有抑制作用,而且此抑制作用随着金属离子剂量的增加及作用时间的延长更加显著,Cu~(2+)和Cd~(2+)对藻体的半数抑制浓度(96 h EC50)分别为0.125和0.551 mg/L;而浓度范围为0–80 mg/L的Pb~(2+)对藻体的生长则表现为低剂量(≤40 mg/L)呈促进,高剂量(≥80 mg/L)则抑制。【结论】从凡纳滨对虾养殖池中分离鉴定出一株形态呈螺旋型的拟柱孢藻,命名为螺旋拟柱孢藻(Cylindrospermopsis raciborskii helix),本藻株活体能够在一定浓度的Cu~(2+)、Cd~(2+)和Pb~(2+)中生长,为螺旋拟柱孢藻活藻生物吸附重金属离子而改善虾池水体环境提供了可能性。     

Effect of cadmium and calcium treatments on phytochelatin and glutathione levels in citrus plants

Industry residues, phosphate fertilisers and wastewater as a source of irrigation have considerably increased levels of heavy metals in the soil, mainly cadmium (Cd²⁺). To test the effects of a calcium (Ca²⁺) treatment on Cd²⁺ accumulation and plant tolerance to this heavy metal, plants of two citrus genotypes, Cleopatra mandarin (CM) and Carrizo citrange (CC), were watered with increasing concentrations of Cd²⁺, and phytochelatin (PC) and glutathione (GSH) content were measured. Both genotypes were able to synthesise PCs in response to heavy metal intoxication, although CM seems to be a better Cd²⁺ excluder than CC. However, data indicate that CC plants had a higher capacity for regenerating GSH than CM plants. In this context, the effects of Ca²⁺ treatment on Cd²⁺ accumulation, plant survival and PC, GSH and oxidised glutathione (GSSG) content were assessed. Data indicate that treatment with Ca²⁺ had two positive effects on citrus physiology: it reduced Cd⁺² uptake into roots and also increased GSH content (even in the absence of Cd²⁺). Overall, the data indicate that although Cd²⁺ exclusion is a powerful mechanism to avoid heavy metal build‐up into photosynthetic organs, the capacity to maintain optimum GSH levels to feed PC biosynthesis could also be an important factor in stress tolerance.     

Differences in the activities of some antioxidant enzymes and in H2O2 content during rhizogenesis and somatic embryogenesis in callus cultures of the ice plant

Callus was obtained from hypocotyls of Mesembryanthemum crystallinum seedlings cultured on two types of medium—germination medium (GM) and callus induction medium (CIM). Following subculture on shoot induction medium SIM1, the callus formed on CIM medium regenerated roots or somatic embryos, while that obtained on GM medium was non-regenerative. The activities of CuZn-superoxidase dismutase (SOD) were comparable in all calli, but the activities of FeSOD and MnSOD varied according to the activity of photosystem II and the regenerative potential of the tissues. Catalase (CAT) activity was related to H₂O₂ concentration and affected by both the culture conditions and the morphogenic potential of the calli. The possible role of CAT, SODs and H₂O₂ in the regeneration of M. crystallinum from callus is discussed.This work is dedicated to Prof. Dr. Hubert Ziegler on his 80th birthday.     

环链虫草Cordyceps cateniannulata对番茄生长和抗氧化酶活性的影响

【目的】评估环链虫草Cordyceps cateniannulata对植物促生和植物抗氧化酶活性的影响。【方法】本研究利用浸种法将环链虫草接种于番茄植物体,在接种后的第30天和60天,通过番茄株高、根长、地上和地下部分的干鲜重指标评价其对番茄生长的影响;在接种后第10、20、30、60和90天,通过选择性培养基分析其在番茄不同组织中的生存情况,使用形态学及DNA序列比对的方法检验所分离菌株与原有菌株的一致性。在处理后的第30天,检测番茄叶片中的过氧化物酶(POD)、过氧化氢酶(CAT)、超氧化物歧化酶(SOD)及丙二醛(MDA)含量,观察环链虫草对番茄的抗氧化酶活性影响。【结果】环链虫草可定殖于番茄幼苗且对番茄生长有显著促进作用,菌株对植株的定殖偏好性分别为根部>茎部>叶部。酶活检测结果表明,处理组番茄叶片防御酶活性均呈显著升高的趋势,其中POD、CAT、SOD活性分别比对照增加了52.21%、75.31%和158.59%,MDA含量下降了35.15%。【结论】环链虫草可以通过浸种的方法感染并定殖番茄幼苗的根、茎、叶,促进番茄幼苗的生长并提高番茄抗氧化酶活性,具有较好的田间...     

Transgenic tobacco plants expressing a rice cysteine synthase gene are tolerant to toxic levels of cadmium

Plants tolerate heavy metals through sequestration with cysteine-rich peptides, phytochelatins. In this reaction, the rate limiting step is considered to be the supply of cysteine, which is synthesized by cysteine synthase (CS, EC 4.2.99.8) from hydrogen sulfide andO-acetylserine. In this study, we transformed tobacco (Nicotiana tabacum) plants withRCS1, a cytosolic cysteine synthase gene of rice (Oryza sativa), and examined their sensitivity to cadmium. The transgenic plants had up to 3-fold higher activity of cysteine synthase than wild-type plants. Upon exposure to cadmium, they exhibited obvious tolerance with much greater growth than wild-type plants. The level of phytochelatins in shoots was higher in transgenic than in wild-type plants after cadmium treatment, suggesting that cadmium was actively trapped by phytochelatins. However, the cadmium concentration per g fresh weight of whole transgenic plants was 20 percnt; lower than that of wild-type plants, suggesting cadmium to be either actively excreted or diluted by fast growth. Genetic analysis of progenies clearly showed segregation of cadmium tolerance, indicating that the trait resulted from the introduced gene. These results suggest that introduction of a cysteine synthase gene into tobacco plants resulted not only in high level production of sulfur-containing compounds that detoxify cadmium, but also in active elimination of cadmium toxicity from plant bodies.     

Effects of cadmium on gene expression in cadmium-tolerant and cadmium-sensitiveDatura innoxia cells

The effect of Cd on gene expression in suspension cultures of twoDatura innoxia cell lines with differing Cd tolerance was studied.In vivo labeling experiments using [³H] leucine showed that Cd induced the synthesis of a similar range of proteins in both cell lines at a concentration which will kill the sensitive but not the tolerant cells. Corresponding changes in levels of translatable mRNA were also observed. The induction of the synthesis of proteins by Cd was transient since Cd-tolerant cells growing continuously in 250 M CdCl₂ contained a similar set ofin vitro translation products to cells growing in the absence of Cd. Although Cd had a similar effect on gene expression in both cell lines, Cd-tolerant cells possess two abundant mRNAs which are constitutively produced. These mRNAs encode proteins of low molecular weight (about 11 kDa) and are either absent or present at a low level in Cd-sensitive cells. The functions of these proteins are not known but they may be involved in the tolerance mechanism. Two-dimensional gel electrophoresis ofin vitro translation products showed that many of the Cd-induced proteins are also induced by heat shock. A 42°C heat shock resulted in agreater range and more intense induction of translatable mRNAs than 4 h exposure to 250 M CdCl₂. However a subset of mRNAs were induced specifically by Cd while other mRNAs were heat shock-specific. There was no difference in the ability of the two cell lines to tolerate heat shock. This was also reflected by the same pattern of major proteins induced by heat shock in the two cell lines.     

Effect of allopolyploidy on the activity of selected enzymes inHibiscus

Mature seeds of diploid and tetraploidHibiscus species were analyzed for enzyme activity (alcohol dehydrogenase, malate dehydrogenase, leucine aminopeptidase), total protein content, DNA amount and dry weight. The recently formed tetraploid,H. radiatus, generally had enzyme and protein levels very similar to the sum of its progenitors, while the more ancient speciesH. acetosella had several lower levels. This difference may reflect the greater amount of timeH. acetosella has had to evolve dosage compensations.Michigan Agricultural Experiment Station Journal Article 9665.A part of this research was used to satisfy the requirements ofA. Hoisington for a M.S. degree at the University of South Carolina.