Effects of Temperature on the In vivo Assay of Nitrate Reductase in some C3 and C4Species

Nitrate reductase (NR) activity was measuredin vivo in differentcrop species at 25–60 °C. Highest NR activity wasobserved at 40 °C in pigeon pea, cowpea, sunflower, sesameand sorghum, 45 °C in maize and 50 °C in bajra. At higherincubation temperatures NR activity declined in all species.In mung bean the optimum incubation temperature varied withthe season. In the summer crop of mung beans, NR activity wasmaximum at 50 °C while in the rainy season crop 30 °Cwas the optimum incubation temperature. NR in sesame was relativelyheat-tolerant. The results indicate that 30 °C is not theoptimum incubation temperature for all crop species. Nitrate reductase, temperature, in vivo assay     

Brachiopod Metabolism and Enzymes

Brachiopods consume oxygen at relatively low rates, and sometimesconsume none at all for hours. Specimens of Terebratulina septentrionalissurvived total anoxia for 3.5 days at 3°C. Isolated tissuesconverted ¹⁴Cµglucose into eight carboxylic acids at anaverage rate of 1.5 x 10^–10 mole/SOL;hr per g tissue.Carbon from labelled glucose flowed steadily into citric acidand into an unknown acid for 2 hours under both aerobic andanaerobic conditions. In the first hour, more label was foundin malic acid after aerobic incubation, and more label in succinicacid after anaerobic incubation, while the fraction in lacticacid was the same. Terebratulina carried on a mixed fermentationboth in the presence and in the absence of oxygen. The inarticulate Glottidia pyramidata has a succinate dehydrogenasewith kinetic properties favoring succinate oxidation, whilethe Terebratulina enzyme is more likely to operate in the reversedirection. Lactate metabolism is relatively unimportant in bothspecies. Information on nitrogen-compound metabolism is limited to theinarticulate Lingula reevii, which is ammonotelic. Arginaseand urease activities exceeded those of bivalve mollusks, whileaspartate and alanine aminotransferase rates were both muchlower. Some unique features of DNA, RNA and hemerythrin fromLingula have been discovered in the last few years.     

Temperature and Anoxic Injury in Pea Seedlings

Anaerobic incubation of newly germinated pea seedlings understerile conditions on moist filter paper was used to distinguishbetween the physical effects of excess moisture on soaking injuryand the metabolic consequences of prolonged anoxia. Over a 4d incubation period seedling death after anoxia fell as temperaturewas reduced from 25 to 5 °C. Internal ethanol concentrationsincreased with length of anaerobic incubation but fell withdecrease in temperature. For all combinations of temperaturewith length of anaerobic incubation, seedling survival was alwaysinversely related to ethanol concentration. An internal ethanolconcentration of 60 µM appeared to be a threshold valuefor seedling survival as anoxic death occurred only when thisconcentration was exceeded.     

Soybean Seed Respiration During Simulated Preharvest Deterioration

Rapid decline of seed quality limits soybean production in thelowland tropies. Seed deterioration is promoted by delayed harvestunder high ambient temperature and relative humidity. To evaluatechanges in respiration during deterioration, soybean seed weresubjected to four controlled, constant or fluctuating, watercontent regimes at 25°C and 32°C to simulate the postmaturation,preharvest environment. Seed deteriorated rapidly under highwater content regimes at 32°C and were non-viable by 20d. Low rates of oxygen uptake during early imbibition correlatedwith deterioration and were attributed to a decline in the integrityof the cyanide-sensitive cytochrome pathway. However, tissuessubjected to high water content fluctuation at 32°C for20 d had high rates of oxygen uptake due mainly to ‘residual’respiration. Only small increases in alternative respirationand lipoxygenase activity occurred during deterioration. A markedincrease in ethanol content during imbibition indicated a shiftfrom aerobic to anaerobic metabolism induced by the declinein the cytochrome pathway. A reduction in tetrazolium stainingwas not accompanied by decreased activity of alcohol dehydrogenaseor malate dehydrogenase. Reduced pyruvate metabolism throughthe tricarboxylic acid cycle and a concomitant decline in NADHlevels were proposed to limit dehydrogenase activity in vivocausing the decreased staining of tissues. The mitochondriaappear to be the site of a primary lesion during seed deteriorationunder combinations of high water content and high temperature. Key words: Cytochrome, alternative-respiration, germination     

Influence of Genotype, Plant Growth Temperature and Anther Incubation Temperature on Microspore Embryo Production in Brassica napus ssp. oleifera

Eleven F₁ hybrid genotypes of winter rape (Brassica napus ssp.oleifera) were used in a study of induction and growth of microspore-derivedembryos. Plants of each genotype were grown in controlled environmentsat either a constant 15°C or a constant 20°C, both witha 16 h photoperiod. Equal numbers of buds, approximately 2.5mm in length, containing uninucleate microspores were harvestedfrom each genotype and either pretreated (14 d at 4°C) ordissected immediately after harvest. Anthers were cultured onliquid medium based upon that of Murashige and Skoog (1962)and containing 8% sucrose, 0.5 mg dm^–3 naphthylaceticacid and 0.05 mg dm^–3 benzylaminopurine. Anthers fromequal samples of buds were incubated at 35°C for 0, 1, 2or 3 d before transfer to 30°C (21 d) and then 25°C.After a total of 42 d incubation, cultures were scored for thepresence of macroscopic embryos (1–2 mm in length) andfor the presence of anthers containing aborted embryoids whichhad not developed further. The results showed first that bud pretreatment completely inhibitedinduction and secondly that anthers of all genotypes had anabsolute requirement for a 35°C treatment (optimal duration2 d) in order to induce embryoid formation. In the great majorityof genotypes plants grown at 15°C provided more productiveanthers than plants grown at 20°C. However, within eachtreatment there were great differences both in the frequencyof anthers showing induced embryoids and of the final yieldof embryos. There was evidence that hybrids with a common parentresponded similarly under certain treatments. This confirmedthe importance of genotypic control for some components of embryoyield. Key words: Brassica napus, Rape, Anther culture, Pollen, Haploid     

The Survival of Germinating Orthodox Seeds after Desiccation and Hermetic Storage

Seeds of barley (Hordeum vulgare L.) and mung bean (Vigna radiata(L.) Wilczek), with orthodox seed storage behaviour, were imbibedfor between 8 h and 96 h at 15 °C and 25 °C, respectively,while barley seeds were also maintained in moist aerated storageat 15 °C for 14 d. These seeds and seedlings, together withcontrols, were then dried to various moisture contents between3% and 16% (wet basis) and hermetically stored for six monthsat —20°C, 0°C or 15°C. In both species, neitherdesiccation nor subsequent hermetic storage of the control lotsresulted in loss in viability. The results for barley seedsimbibed for 24 h were similar to the control, but desiccationsensitivity increased progressively with duration of imbibitionbeyond 24 h in barley or 8 h in mung bean; these treatmentsalso reduced the longevity of the surviving seeds in air-drystorage. Loss in viability in barley imbibed for 48 h was mostrapid at the two extreme seed storage moisture contents of 3·6%and 14·3%, and in both these cases was more rapid at15 °C than at cooler temperatures. Similarly, for mung beanimbibed for 8 h, loss in viability was most rapid at the lowest(4·3%) moisture content, but in this case it was morerapid at –20 °C than at warmer temperatures. Thus,these results for the storage of previously imbibed orthodoxseeds conform with the main features of intermediate seed storagebehaviour Key words: Barley, Hordeum vulgare L., mung bean, Vigna radiata (L.) Wilczek, desiccation sensitivity, seed longevity, seed storage behaviour     

Seed Viability Constants for Lettuce

Seeds of two lettuce cultivars (Lactuca sativa L., cv. Meikoninginand cv. Grand Rapids) were hermetically stored with constantmoisture contents ranging between 3.6 and 17.9 per cent (freshweight basis) at constant temperatures ranging between 5 and75 °C. The decline with time in percentage germination andpercentage normal seedlings was determined for each storagetreatment. The data were fitted to an equation which containsthe constants: K₁, the probit of the initial percentage germinationor normal seedlings; K_E, a species constant; C_W, the constantof a logarithmic moisture term; C_H, the constant of a lineartemperature term and C_Q, the constant of a quadratic temperatureterm. Regression analysis of data from storage periods up to5.5 years at temperatures of 5–75 °C and seed moisturecontents of 3.6–13.6 per cent yielded the following values:K_E= 8.218, C_W=4.797±0.163, C_H=0.0489±0.0050 andC_Q=0.000365±0.000056. Although this equation consistentlyprovided a better fit, simplified equations, assuming eithera log-linear relationship between seed longevity and temperature,or a log-linear relationship between seed longevity and bothmoisture content and temperature, accounted for more than 94per cent of the variation at the restricted temperature rangeof 5–40 °C. Longevity of the same seed lots at sub-zero temperatures (–5,–10 and –20 °C) was studied in separate tests.Freezing damage, resulting in abnormal seedlings in the germinationtest, occurred at –20 °C when the moisture contentof the seeds exceeded 12 per cent. No decline in percentagenormal seedlings was observed after a storage period of 18 monthsor longer at –20 °C, provided the seed moisture contentdid not exceed 9.5 per cent. For seeds stored at –5 and–10 °C with 9.6–12.5 per cent moisture content,the observed rate of decline of percentage normal seedlingswas adequately predicted by the viability equation, using theabove values for the constants. This suggests that for low moisturecontents the viability equation can be applied to estimate longevityat sub-zero temperatures. Lettuce, Lactuca sativa (L.), seed longevity, seed storage, viability constants, storage conditions     

Biosynthesis of Volatiles in Brown Boronia Flowers after Harvest: Effect of Harvest Time and Incubation Conditions

Brown boronia flowers (Boronia megastigma)were incubated at25 °C after harvest, increasing the concentration of a solventextracted product by up to 25% (d. wt basis) and floral volatilesby up to 300% (d. wt). Open flowers produced more volatilesduring post-harvest incubation than flower buds, whole flowersproduced more than flowers treated to simulate harvester damage,and fresh flowers produced more than frozen and thawed flowers.Flowers incubated in bags purged with air produced more extractand volatiles than those purged with nitrogen gas; ß-iononewas particularly depleted in nitrogen-purged flowers. Flowersand buds from three successive harvests (68, 82 and 90% openflowers) were incubated at several temperatures for up to 24h. The greatest increase in the concentration of floral extractoccurred in flowers harvested when 90% were open and incubatedfor 4 h at 12 °C, or 14 h at 23 °C. The largest increasein total volatiles occurred in material harvested at 82% openflowers and incubated for 25 h at 12 °C, or 13 h at 23 °C.The concentration of extract and volatiles declined after prolongedpost-harvest incubations. Brown boronia flowers produce volatilesand other components of the floral extract after harvest whenflowers with mature, intact enzyme systems are well suppliedwith oxygen, at temperatures at or below 25 °C. As flowersbecome visibly senescent, their ability to produce volatilesafter harvest declines.Copyright 1998 Annals of Botany Company Boronia megastigma(Nees); brown boronia; essential oils; floral volatiles; ß-ionone; phenology; post-harvest storage.     

Effects of exogenous abscisic acid (ABA) on cucumber seedling leaf carbohydrate metabolism under low temperature

Seedlings with four true leaves of cucumbers (Cucumis sativus L.), Guonong No.25 (a cold-tolerant cultivar) and Guonong No.41 (a cold sensitive cultivar), were grown under normal or low temperature conditions: 25°C/18°C or 15°C/8°C (day/night). The seedlings of Guonong No.25 under low temperature were also treated with or without exogenous ABA. The purpose of our study was to find out the effects of low temperature and exogenous ABA application on the carbohydrate metabolism in the cucumber plants. Time course changes of carbohydrate contents and activities of stachyose synthase and alkaline α-galactosidase in the seedling leaves were investigated after the treatment. Our results show that compared to the seedlings under temperatures of 25°C/18°C, the seedlings of the both tested genotypes under 15°C/8°C (day/night) have significantly higher contents of all measured soluble carbohydrates. Significant difference in stachyose synthase activity is observed between the two genotypes under normal temperature or low temperature. Under normal temperature, leaf stachyose synthase activity in Guonong No.41 is higher than that in Guonong No.25. The stachyose synthase activity of Guonong No.41 decreases sharply under low temperature, but that of Guonong No.25 increases 3 days after treatment and then decreases to the original level. In contrast, there is no significant genotypic difference in alkaline α-galactosidase activity. Additionally, compared to the control seedlings treated with 0 μM ABA, the seedlings treated with 50 and 150 μM ABA accumulate substantial amounts of all tested soluble carbohydrates except galactose whereas 250 μM ABA treated seedlings show decreased levels of all these soluble carbohydrates. Stachyose synthase activity increases significantly upon 50 and 150 μM ABA treatments. Fan-zhen Menga, Li-ping Hu, and Shao-hui Wang contributed equally to the paper.     

Germination of Tagetes minuta L. I. Temperature Effects

Initial studies have indicated that Tagetes minuta achenes haveboth a temperature and a light requirement for germination.Temperatures tested were 10, 20, 25, 30 and 35 °C. Germinationwas optimal at 25 °C under white light conditions. Underthese conditions 100 per cent of achenes germinated within 7days of imbibition. There was no germination at 10 or 35 °Ceither in the light or in the dark. Achenes imbibed and incubatedat 35 °C for 4 days showed no visible signs of germinationbut on transfer to 25 °C, 100 per cent of these achenesgerminated within 24 h. Furthermore, achenes given this hightemperature (35 °C) treatment could be dried at 25 °C,re-imbibed at 25 °C and again 100 per cent of achenes germinatedwithin 24 h of re-imbibition. This rapid germination responsefollowing removal from the high temperature regime could alsobe induced by transfer to temperatures of 20 °C or 20 °C(16 h) alternating with 10 °C (8 h). Tagetes minuta L., weed seeds, germination, temperature, light     

The Effect of Temperature on Reproduction in FivePrimulaSpecies

Primula vulgarisHuds.,P. verisL.,P. frondosaJanka, and threepopulations ofP. farinosaL. were legitimately and illegitimatelypollinated, and the self-fertileP. scoticaselfed and cross-pollinatedand then subjected to uniform temperature conditions of 6, 15or 26 °C for 4 d before gynoecia were examined for pollengermination and pollen tube growth, or plants progressed toseed set at 15 °C, after which seeds were weighed, germinated,and seedlings grown on. The temperature responses of pollengermination and pollen tube growth were not always congruent,and varied between species, populations, and often between morphs(pin and thrum) in the distylous species. Nevertheless, optimaltemperature responses tended to be lower for vernal species(P. vulgarisandP. veris) and for subarcticP. scoticathan forlater flowering montane species. However, no relationship wasfound between pollen temperature response, and fertility. Thegreatest seed set occurred after legitimate pollination at 15°C in most cases; a flowering temperature of 26 °C tendedto impede seed set, except forP. scoticaand the low altitudepopulation ofP. farinosa. InP. veris, P. frondosaand the highaltitude population ofP. farinosa,some illegitimate pollen germinationand pollen tube growth occurred at 26 °C, but this did notlead to increased within-morph seed set in these self-incompatiblespecies at this relatively high temperature. Temperature atflowering frequently affected average seed weight, and inP.verisand two populations ofP. farinosathis attribute may havebeen influenced by seed number, the average seed weight of few-seededcapsules tending to be greater than for many-seeded capsules.A high seed weight might mitigate the disadvantageous effectsof low fecundity resulting from interactions with floweringtemperature. However, inP. vulgarisandP. scoticainteractionsbetween flowering temperature and seed weight may have other,undetermined, causes. The seed of four species germinated leastwell in standard conditions when set following a flowering temperatureof 6 °C, which tends to support the hypothesis that temperatureat flowering can affect seed physiology; in contrast the seedof the two upland populations ofP. farinosagerminated leastwell after flowering at 26 °C. We conclude that much morework is needed on interactions between temperature and reproductiveefficiency, but that preliminary indications suggest that aglobal increase in temperature at flowering might adverselyaffect the quantity and quality of seed set in some species.Copyright1998 Annals of Botany Company Distyly, pollen tube,Primula farinosa, Primula frondosa, Primula scotica, Primula veris, Primula vulgaris,reproduction, seed set, temperature.     

Shoot Elongation in Scots Pine: Diurnal Variations and Response to Temperature

Kanninen, M. 1985. Shoot elongation in Scots pine: Diurnal variationsand response to temperature.—J. exp. Bot. 36: 1760–1770. Time series analysis is used to study the diurnal variationsin the rate of shoot elongation of Scots pine (Pinus sylvestrisL.) seedlings, and its response to temperature. The shoot elongation of three 5-year-old Scots pine seedlingswas measured at 2 h intervals over a 12 d period in June 1979.Ambient temperature, measured with a thermocouple, was continuouslyrecorded during the same period. The measurements were carriedout in the field. Time series analysis of the data was carried out by estimatedauto-correlation and partial auto-correlation functions. A multiplicative‘seasonal’ model was applied to both the input andoutput series to ‘prewhiten’ the data set. Serialcross-correlation analysis of the prewhitened series was usedto identify the structure of the transfer function model betweentemperature and growth rate. There was a phase shift between the air temperature and shootextension. The cross-correlation function peaked at 2 h lagvalue. The influence of temperature on the growth rate was adequatelydescribed by a first-order transfer function model. The characteristicfeature of the model was a time constant of 3.3 h and a basetemperature of 6.3 °C for the response of shoot elongationto temperature. Key words: Scots pine, Pinus sylvestris L., shoot elongation, temperature response, time-series analysis     

Effect of various exogenous and endogenous factors on microspore embryogenesis in Indian mustard (<Emphasis Type="Italic">Brassica juncea</Emphasis> (L.) Czern and Coss)

Summary The influence of donor plant growth environment, microspore development stage, culture media and incubation conditions on microspore embryogenesis was studied in three Indian B. juncea varieties. The donor plants were grown under varying environments: field conditions, controlled conditions, or a combination of the two. The correlation analysis between the bud size and microspore development stage revealed that the bud size is an accurate marker for donor plants grown under controlled conditions, however, the same does not hold true for the field-grown plants. The buds containing late uninucleate microspores collected from plants grown under normal field conditions up to bolting stage and then transferred to controlled environment were observed to be most responsive with genotypic variability ranging from 10 to 35 embryos per Petri dish, irrespective of the other factors. NLN medium containing 13% sucrose was found to be most suitable for induction of embryogenesis The fortification of this medium with activated charcoal, polyvinylpyrrolidone, colchicine, or growth regulators (6-benzylaminopurine and 1-naphthaleneacetic acid) was observed to be antagonistic for microspore embryogenesis, while silver nitrate (10 μM) had a significant synergistic effect. A post-culture high-temperature incubation of microspores at 32.5±1°C for 10–15 d was found most suitable for high-frequency production of microspore embryos. The highest frequency of microspore embryogenesis (78 embryos per Petri dish) was observed from the late uninucleate microspores (contained in bud sizes 3.1–3.5 nm irrespective of genotype) cultured on NLN medium containing 13% sucrose and silver nitrate (10 μM), and incubated at 32.5°C for 10–15 d.     

Geographical Transition of Sylleptic/Proleptic Branching in Three Cinnamomum Species with Different Bud Types

Three native Japanese Cinnamomum(Lauraceae) species exhibiteither sylleptic and proleptic, or proleptic branching dependingon species-specific types of bud-structure (hypsophyllary andscaled-buds) and geographical distribution. Major branchingshifted from sylleptic at the axils of cataphylls and hypsophyllsin the southernmost C. doederleinii(latitudinal distributionrange 24–28° N) to both sylleptic at cataphyllary-and proleptic at hypsophyllary-axils in mid-latitudinal C. daphnoides(27–33°N), and to proleptic at the axils of foliage-leaves in the northernmostspecies C. japonicum(25–37° N). In all three Cinnamomumspecies, the sylleptic and proleptic branches expand aroundthe boundary between two successive yearly shoot-modules. Thepredominant, fertile axils having branches shifted from cataphylls(n year) and hypsophylls (n-1 year) in C. doederleinii and C.daphnoides, to foliage-leaves (n-1) in C. japonicum. The budsof proleptic branches at the axils of hypsophylls and foliage-leavesinevitably experience winter dormancy, hence the shoots areequipped with protective cataphylls instead of a hypopodium.Shoot length and leaf number gradually increased from the mostdistal cataphyllary sylleptic (n) shoots towards the most basalproleptic shoots at the axils of foliage-leaves (n-1). Prolepticshoots at the axils of foliage-leaves perform similarly to mainshoots in all three Cinnamomum species studied. The relativenumber of leaves borne on proleptic shoots gradually increasedfrom C. doederleinii, to C. daphnoides, and C. japonicum. Underthe seasonal, short growing periods of temperate latitudes,the increased shoot performance and bud protection of prolepticshoots are made possible through the earlier onset of bud formation(prolepsis) at the axils of the previous year's hypsophyllsand/or foliage-leaves in trees with rhythmic growth. Copyright2001 Annals of Botany Company Syllepsis, prolepsis, bud type, cataphyll, hypsophyll, shoot-growth cycle, evergreen broad-leaved tree, Cinnamomum doederleinii, Cinnamomum daphnoides, Cinnamomum japonicum     

Influences of Water Status, Temperature, and Root Age on Daily Patterns of Root Respiration for Two Cactus Species

Daily patterns of root respiration measured as CO₂, efflux werestudied at various soil water potentials, temperatures, androot ages for individual, attached roots of the barrel cactusFerocactus acanthodes and the platyopuntia Opuntia ficus-indica.The daily patterns of root respiration for both establishedroots and rain roots followed the daily patterns of root temperature.Root respiration increased when root temperature was raisedfrom 5 °C to 50 °C for F. acanthodes and from 5 °Cto 55 °C for O. ficus-indica; at 60 °C root respirationdecreased 50° from the maximum for F. acanthodes and decreased25° for O. ficus-indica. Root respiration per unit d. wtdecreased with root age for both species, especially for rainroots. Root respiration rates for rain roots were reduced tozero at a soil water potential (     

Low Temperature Storage of Caryopses of Triticum durum: Viability and Longevity

Germination of Triticum durum Desf. ‘Cappelli’ caryopsesstored in hermetically-sealed containers at 10°C or -20°Cwas analysed. Caryopses were maintained in laboratory conditions(20 ± 4°C) prior to controlled storage, which began5 d, 240 d and 7 years after harvesting. In addition, after9 years of storage, one 10°C stored batch of caryopses andtwo -20°C stored batches were returned to laboratory conditions.Germination over time and seed longevity were investigated.Results showed that: (1) under laboratory conditions, caryopsesin relative (primary) dormancy at the beginning of storage hadlost dormancy after 45 d and germination ability was lost bythe end of year 7. (2) When stored at 10°C, relative dormancyin caryopses was lost within 1 year, but 100% germination abilitywas retained after 23 years of storage. (3) When stored at -20°C,caryopses that were dormant at the beginning of storage (5 dafter harvesting) maintained this condition for 23 years whilecaryopses which were placed in storage 240 d after harvesting,when relative dormancy had already been broken, maintained 100%germination ability. Caryopses returned to laboratory conditionsafter 9 years of storage at 10°C or -20°C showed thesame trend as caryopses maintained exclusively in laboratoryconditions since the time of harvesting. Caryopses removed from-20°C overcame relative dormancy in 50 d and maintainedgermination ability for roughly 7 years, while those removedfrom 10°C lost the ability to germinate by the end of thefifth year. Copyright 2000 Annals of Botany Company Germination, longevity, low-temperature-storage, Triticum durum, viability     

Predicting spring frost sensitivity by bud development and temperature sum in Norway spruce seedlings

Nurseries would benefit greatly if frost hardiness (FH) of seedlings could be predicted by some environmental variable or by bud development in spring. We investigated the FH of 1-year-old Norway spruce (Picea abies (L.) Karst.) seedlings of local origin. The seedlings were stored frozen until incubated in the growth chamber at six different temperature sums (TSs) (0, 55, 88, 142, 185 and 240 d.d., >5°C) from mid-February to mid-March. FH of the buds, stems and previous year needles was assessed on three occasions. When the TS was 88 d.d. or less, buds exhibited only microscopic signs of development, even when seedlings tolerated temperatures below −10°C. As TS increased, primordial needles and primordial stems of buds grew while FH weakened, especially in previous year needles. When the TS was at least 142 d.d., all plant parts were frost hardy to approximately −6°C. Monitoring TS and bud development can help predict FH of Norway spruce seedlings in spring. However, more studies with seedlings of different ages and from multiple locations are necessary to appreciate the generality of our results.     

Studies on the Fragmented Shoot Apex of Grapevine: III. A SCANNING ELECTRON MICROSCOPE STUDY OF ADVENTITIOUS BUD FORMATION IN VITRO

Scanning electron microscopy (SEM) was used to provide directevidence that shoots produced in vitro from fragmented shootapices of grapevine were adventitious in origin. The effectof temperature on the formation of the adventitious buds wasalso examined using SEM. At 27°C, shoot buds were initiatedby 31 d following fragmentation of the apex, while at 35°Cshoot initiation and multiplication were already well-advancedat only 18 d after the start of culture. At 38°C, apicalfragments quickly browned and died. After 25 d at 35°C,structures resembling inflorescence primordia were also visible.These did not occur in cultures at 27°C. The primordia laterdeveloped into multiple-branched tendrils, structures whichappear to be intermediate between tendrils and inflorescencesand have not been previously described.     

Development of the Fifth Leaf is Indicative for Whole Plant Performance at Low Temperature in Tomato

In the search for early-detectable selection criteria for growthat low temperature conditions in tomato, first the initiationand growth of individual leaves was analysed. Scanning electronmicroscopy revealed that the first four primordia had alreadydeveloped during the germination period at 25°C. The primordiumof the fifth leaf, however, was initiated after the transferof seedlings to the experimental conditions. The increase inlength of the first three leaves, and to a lesser extent ofthe fourth leaf, was considerably smaller in comparison withthat of later formed leaves. Moreover, the morphology of thefirst three to four leaves was deviant, whereas the others showedthe normal compound leaf architecture. All these results indicatedthat the fifth leaf was the earliest formed leaf with growthcharacteristics that might reflect the growth potential of thewhole plant. Development of the fifth leaf was tested as a marker for wholeplant growth. At three temperature, 18, 15 and 12°C, growthresponses of the fifth leaf were similar to that of whole plantsin four tomato genotypes: Line A, Line B, Premier and MXXIV-13.Significant differences in relative growth rate of dry weightof whole plants and fifth leaves (RGR_W)and of leaf area of thefifth leaves (RGR_LA between two fast growing and two slow growinggenotypes were found. No genotype by temperature interactionfor RGR_W and RGR_LA was found, indicating that the effect oftemperature decrease was similar for the four genotypes. The structure of the mature fifth leaf of one fast and one slowgrowing genotype, Line A and MXXIV-13, was analysed. For bothgenotypes, leaves were small and thick at low temperature, 12°C.The total number of epidermis and palisade parenchyma cellsper leaf was smaller but the size of the cells developed at12°C was larger than at 18°C. Consequently, the slowgrowth at 12°C was due to a low rate of cell division. Atboth temperatures, the fifth leaf to MXXIV-13 was smaller comparedto that of line A. Since the size of the cells were similar,the smaller leaf size was due to lower number of leaf cells. The results confirm the suitability of the growth, especiallyexpressed as RGR_LA , of the fifth leaf as a nondestructive marketfor vegetative development of tomato at low temperature. Growthdifferences between genotypes were mainly reflected by differencesin cell number of leaves, which might be correlated with geneticallydetermined differences in cell number of leaf primordia.Copyright1993, 1999 Academic Press Lycopersicon esculentum Mill. genotypes, plant growth, selection criteria, low temperature, leaf initiation, leaf development, RGR, leaf structure, cell expansion