Effects of IAA and BA on development of globular,heart- and torpedo-stage embryos from cell suspensions of three grape genotypes

In order to initiate cell and embryo suspensions, embryogenic calluses derived on NN solid medium with 2,4-D and BA from petioles of in vitro grown plants of three interspecific grapevine hybrids were cultured in three versions of liquid NN medium: (1) without growth regulators, (2) 0.1 mg l⁻¹ IAA and (3) 0.5 mg l⁻¹ BA. Cell and embryo suspensions were incubated two and three times in these versions of liquid media in various combinations. Incubating suspensions two times in hormone-free media and/or with 0.1 mg l⁻¹ IAA led to formation of globular embryos in the three cultivars studied and small numbers of heart-stage embryos in ‘Podarok Magaracha’ and ‘Intervitis Magaracha’. Numerous heart-stage embryos developed in ‘Intervitis Magaracha’ and ‘Podarok Magaracha’ when the suspensions had been initiated in medium with 0.5 mg l⁻¹ BA, and in ‘Bianca’ this was achieved after two incubations in the above medium. Torpedo-stage embryos were formed after subculturing heart-stage embryo suspensions in medium with 0.1 mg l⁻¹ IAA in all study cultivars. If only small numbers of embryos of a certain developmental heart- or torpedo- stage were formed, such cell and embryo suspensions need to be repeatedly subcultured in liquid medium with specific growth regulators to enable this process.     

In vitro induction of tetraploid ginger (Zingiber officinale Roscoe) and its pollen fertility and germinability

In vitro induction of tetraploid ginger (Zingiber officinale Roscoe) and its pollen fertility and germinability were investigated. The growth of shoot tip cultures on agar MS medium containing 2.0 mg l⁻¹ BA was greater than that of similar cultures in liquid MS medium with the same BA concentration. In liquid medium, the combinations of 0.5, 1.0, or 2.0 mg l⁻¹ BA with 0.05 mg l⁻¹ NAA tended to enhance the growth of the cultures. The efficiency of tetraploid induction was assessed by treating shoot tip explants on agar or in liquid MS medium containing 2.0 mg l⁻¹ BA, 0.05 mg l⁻¹ NAA, and 0.2% (w/v) colchicine for 4, 8, 12, and 14 days. The total number of tetraploids induced on solid medium was 18, but only five in liquid medium. On both media, the colchicine treatment for 8 days gave the maximum level of tetraploid induction. Therefore, it was found that the treatment of shoot tip explants on agar medium containing 2.0 mg l⁻¹ BA, 0.05 mg l⁻¹ NAA, and 0.2% (w/v) colchicine for 8 days was the most efficient way of inducing tetraploid ginger. Induced tetraploid strains, ‘4× Kintoki’, ‘4× Sanshu’, and ‘4× Philippine cebu 1’, had higher pollen fertility and germinability than the diploid counterparts, i.e., in the diploid strains, pollen fertility ranged from 0.3 to 6.2% and the germination rate from 0.0 to 0.1%, while in the tetraploid strains, pollen fertility ranged from 27.4 to 74.2% and the germination rate from 4.8 to 12.9%.     

Prohexadione-calcium affects growth and flowering of petunia and impatiens grown under photoselective films

The response of petunia (Petunia x hybrida Vilm.-Andr. ‘Countdown Burgundy’) and impatiens (Impatiens wallerana Hook ‘Accent Orange Tempo’) to Prohexadione-calcium was evaluated under a clear and a far-red light absorbing greenhouse (A_FR) film to investigate the dosage effect of Prohexadione-Ca and to determine if it can overcome the flowering delay under FR deficient greenhouse environments. Prohexadione-Ca reduced stem elongation of petunia and impatiens under A_FR and clear films when applied 3 weeks after germination. Late applications were less effective. In both crops, main stem length decreased in a quadratic pattern as the concentration of Prohexadione-Ca increased. Under both films, 50–100 mg l⁻¹ Prohexadione-Ca resulted in ≈30% shorter petunia plants. Greater concentrations (500 and 1000 mg l⁻¹) resulted in excessively short plants (over 70%). Prohexadione-Ca at 100 mg l⁻¹ delayed anthesis of petunia by 8 and 3 days under the clear film and the A_FR film, respectively during less inductive photoperiods but had no effect during inductive photoperiods. In impatiens, Prohexadione-Ca at 100 mg l⁻¹ delayed anthesis over 10 days under clear or A_FR film. Greater concentrations (200 and 300 mg l⁻¹) inhibited flowering of impatiens. Prohexadione-Ca treatments significantly affected flower color development. Untreated petunia plants had dark burgundy flowers. Prohexadione-Ca treatment increased L*, a*, and C* values and decreased hue angle indicating that the flowers were faded. Flowers of untreated impatiens plants were bright orange color. Prohexadione-Ca at 100 mg l⁻¹ increased L* value and decreased a*, b*, and C* values indicating that significant petal fading had occurred. Flowers of treated plants were nearly white under both films. Although effective in height control, loss of color would be a major limitation to the use of Prohexadione-Ca on flowering crops.     

Methyl jasmonate and CMN-pyrazole applied alone and in combination can cause mature orange abscission

Methyl jasmonate (MJ) and CMN-pyrazole alone and in combination were applied to ‘Hamlin’ and ‘Valencia’ orange trees (Citrus sinensis (L.) Osbeck) in seven separate experiments in the 1998/1999 and 1999/2000 growing seasons to induce abscission of mature fruit for mechanical harvesting. MJ alone significantly reduced fruit detachment force (FDF) of ‘Hamlin’ oranges at concentrations of 10 mM and higher. However, MJ at 20 and 100 mM caused significant defoliation. For ‘Hamlin’ oranges, the most effective treatments were those combining 10 mM MJ and 50 mg l⁻¹ CMN-pyrazole, and 20 mM MJ and 25 mg l⁻¹ CMN-pyrazole. ‘Valencia’ oranges did not respond to 10 mM MJ treatments alone or in combination with CMN-pyrazole, and required MJ at 20 mM in combination with CMN-pyrazole to loosen this late-maturing variety to below 50 N, but excessive defoliation occurred.     

Effect of phytohormones on in vitro shoot multiplication and rooting of lime Citrus aurantifolia (Christm.) Swing

Multiple shoots were produced from node explants of lime (Citrus aurantifolia (Christm.) Swing) on MS medium supplemented with 6-benzylaminopurine (BAP), 6-furfurylaminopurine (kinetin) and α-naphthaleneacetic acid (NAA). The highest number of shoots, nine shoots per node, were produced on a medium containing 2 mg l⁻¹ BAP (8.8 μM), 1 mg l⁻¹ kinetin (4.6 μM) and 1 mg l⁻¹ NAA (5.4 μM). Depending on the concentration of BAP and kinetin, NAA either inhibited, stimulated or did not affect shoot multiplication, which also depended on the cytokinin level. Maximum shoot length was obtained from treatments containing 0.5 mg l⁻¹ BAP (2.2 μM) combined with 1 mg l⁻¹ kinetin (4.6 μM) and 0.5 mg l⁻¹ NAA (2.7 μM). The largest leaves of resultant shoots were produced on a medium containing 0.5 mg l⁻¹ each of kinetin (2.3 μM) and NAA (2.7 μM). Transferring in vitro shoots to rooting media containing indole-3-butyric acid (IBA) and NAA produced complete plantlets. The highest rooting percentage was obtained on a medium containing either 1 mg l⁻¹ NAA (5.4 μM) alone or 0.5 mg l⁻¹ NAA (2.7 μM) combined with 2 mg l⁻¹ IBA (9.6 μM), whereas the highest number of roots were produced on a treatment containing both 2 mg l⁻¹ NAA (10.8 μM) and 2 mg l⁻¹ IBA (9.6 μM). Roots elongated most on treatments containing 0.5 mg l⁻¹ of either NAA (2.7 μM) or IBA (2.4 μM). Shoot growth associated with the rooting phase was the highest in response to 2 mg l⁻¹ IBA (9.6 μM) or 0.5 mg l⁻¹ NAA (2.7 μM). Plantlets that survived acclimatization, 82%, exhibited normal growth in soil under greenhouse conditions.     

Factors affecting the shoot multiplication of Persian walnut (Juglans regia L.)

A number of experiments were conducted to identify suitable procedure for in vitro shoot multiplication of Persian walnut (Juglans regia L.). Three different nutrient media (DKW, MS and WPM) and three different gelling agents (Phytagel, Difco Bacto agar and a mixture of Phytagel and Difco Bacto agar) were studied in the first experiment. Driver and Kuniyuki walnut (DKW) medium solidified with 2.2 g l⁻¹ Phytagel was found optimum. Performance of explants was better on DKW medium than on MS and WPM. The DKW and MS media were not significantly different from each other, but both of them were significantly better than WPM, which was a very poor medium for this species. Phytagel alone was significantly better than Difco Bacto agar or Phytagel combined with Difco Bacto agar. In another experiment different concentrations of BA were studied. Medium containing 1.0 mg l⁻¹ BA and 0.01 mg l⁻¹ IBA was the best, although medium containing 0.6 and 0.8 mg l⁻¹ BA were also successful, and utilisation of 0.4 mg l⁻¹ BA and 0.01 mg l⁻¹ IBA was optimum for shoot elongation. Application of different kinds of auxins (IAA, IBA and NAA at 0.01 or 0.1 mg l⁻¹) with 1.0 mg l⁻¹ BA were also studied. Media containing IBA were significantly better than media containing IAA for shoot fresh weight, but neither of them was significantly different from media containing NAA. Application of 0.01 mg l⁻¹ or 0.1 mg l⁻¹ auxin, with 1.0 mg l⁻¹ BA, was not significantly different for shoot multiplication of Persian walnut. The morphology of shoots on media containing 0.01 mg l⁻¹ IBA was the best.     

Foliar treatment of Mn deficient ‘Washington navel’ orange trees with two Mn sources

The objective of this study was the comparison of the effect of two Mn sources (MnSO₄·H₂O, MnEDTA) which were applied at various concentrations (0, 200, 400, 800, and 1200 mg Mn l⁻¹) to the leaves of ‘Washington navel’ orange trees in order to correct Mn deficiency.One hundred and seventy days after the foliar application of Mn solutions, the mean Mn concentrations in the leaves treated with MnSO₄·H₂O (200, 400, 800 or 1200 mg Mn l⁻¹) or MnEDTA (400, 800 or 1200 mg Mn l⁻¹) were significantly higher than those of the control leaves. Manganese sulfate (MnSO₄·H₂O) was more effective than MnEDTA regarding the improvement of the leaf Mn concentrations of the trees, when applied at equal Mn concentrations. Finally, the leaf Mn concentrations were in the sufficiency range (>25 mg kg⁻¹ d.w.), only after the application of 800 or 1200 mg Mn l⁻¹ as MnSO₄·H₂O.     

The influence of NaCl salinity on growth,yield and fruit quality of strawberry cvs. ‘Elsanta’ and ‘Korona’

In a 2-year field study, strawberry cvs. ‘Elsanta’ and ‘Korona’ were exposed to three different levels of NaCl salinity supplied as aqueous solutions characterised by electrical conductivities of 0.3 dS/m, 2.6 dS/m, and 5.1 dS/m. Salinity in the rhizosphere reduced plant growth by up to 44% in ‘Korona’ and 90% in ‘Elsanta’. A rather distinct cultivar difference represented the reduction in leaf area per plant of 85% in the second year of experiment in ‘Elsanta’ compared to 29% in ‘Korona’. Strawberry can be regarded as a Na⁺ excluder, because Na⁺ content of both strawberry cultivars remained below 3 mg g⁻¹ dry mass at all salinity levels. Cl⁻ content increased considerably, up to 70 mg g⁻¹ dry mass in ‘Korona’ and 80 mg g⁻¹ dry mass in ‘Elsanta’ plants. ‘Korona’ retained most of its Cl⁻ in roots and crowns, whereas in ‘Elsanta’ the maximum was detected in petioles. ‘Korona’ was able to accumulate up to 33% higher Cl⁻ content in the roots than ‘Elsanta’. Macronutrient deficiency due to NaCl salinity was not observed and in comparison to ‘Elsanta’, higher Cl⁻ content in roots of ‘Korona’ did not coincide with an impairment of macronutrient uptake. Salinity stress reduced fruit yield by up to 27% in ‘Korona’ and 64% in ‘Elsanta’. Fruit quality, characterised as taste, aroma, and texture by a consumer-type panel, decreased by more than 24% in ‘Elsanta’, but in ‘Korona’ differences were insignificant. Total soluble solids (Brix) and the ratio Brix/TA (TA, titratable acid) decreased significantly by about 20% in ‘Korona’ and 35% in ‘Elsanta’. To summarise, the ability of ‘Korona’ to retain Cl⁻ in the root system more effectively than ‘Elsanta’ resulted not only in a 41% lower leaf Cl⁻ content at the highest salinity level and a better growth under NaCl stress, but also in a relatively higher fruit yield and fruit quality.     

Double-phase in vitro culture using sorbitol increases shoot proliferation and reduces hyperhydricity in Japanese pear

This study aimed to improve in vitro shoot proliferation efficiency without inducing hyperhydricity in Japanese pear. The shoot number increased at 2.5–10.0 mg l⁻¹ benzyladenine (BA), while shoot fresh mass increased at 1.0 and 2.5 mg l⁻¹ BA. Different macroelement formulation did not affect shoot proliferation, but adding activated charcoal (AC) to the medium inhibited markedly the production of axillary shoots and biomass and many shoots were hyperhydric. Different carbon sources (CS) significantly increased the shoot number and fresh mass, with the best results for shoot proliferation at 20–30 g l⁻¹ sorbitol. With gelling agents, the shoot number increased at 0.4 and 0.6% agar and 0.3% gellan gum, while fresh mass increased at 0.4% agar. The hyperhydric explants were more than 30% at 0.4–0.6% agar and at any concentration of gellan gum. The improved culture (woody plant (WP) supplemented with 20 g l⁻¹ sorbitol, 0.1 mg l⁻¹ 3-indolyl-butyric acid (IBA), 2.5 mg l⁻¹ BA and 0.8% agar) and double-phase culture (the same medium using a double-phase liquid-gelling agent solidified culture system) produced a higher number of axillary shoots than the conventional culture (1/2MS supplemented with 0.1 mg l⁻¹ IBA, 1.0 mg l⁻¹ BA, 30 g l⁻¹ sucrose and 0.8% agar), moreover, double-phase culture had a higher fresh mass than the other cultures.     

Establishment and plant regeneration of somatic embryogenic cell suspension cultures of the Zingiber officinale Rosc.

Somatic embryogenic cell suspension cultures of four ginger cultivars were established. Somatic embryogenic calli were induced from ginger shoot tips on MS agar medium supplemented with 1.0 mg l⁻¹ 2,4-D and 0.2 mg l⁻¹ Kn, which contained only half concentration of NH₄NO₃. Rapid-growing and well-dispersed suspension cultures were established by subculturing this kind of callus in the same liquid MSN medium. The suspension cultures (about 1–2 mm in diameter) were placed on the MSN agar medium for callus proliferation. Thereafter embryogenic callus (1.5 cm²) was transferred to solid media (MS + 0.2 mg l⁻¹ 2,4-D + 5.0 mg l⁻¹ BA + 3% sucrose + 0.7% agar). Somatic embryos produced shoots and roots, and shoots developed into complete plantlets on solid MS medium supplemented with 3.0 mg l⁻¹ BA and 0.1 mg l⁻¹ NAA. The relationship between the DW of suspension cultures and pH changes in medium is also discussed. The suspension cultures still kept their vitalities after subculture for 8 months.     

Micropropagation of Karonda (Carissa carandas) through shoot multiplication

Shoot tips from field grown, mature plants of Carissa carandas cv. Pant Sudarshan were cultured on Murashige and Skoog’s (MS) basal medium supplemented with benzyladenine (BA) and indolebutyric acid (IBA) during different seasons. The maximum sprouting rate was obtained with 1.5 cm long explant collected in spring season (February–March) followed by those collected in summer season (April–June). Shoot proliferation was highest on MS basal media supplemented with 3.0 mg l⁻¹ BA. Rooting of microshoots was noted to be the best in 1/2 MS plus 0.8 mg l⁻¹ IBA and 0.2 mg l⁻¹ naphthalene acetic acid (NAA). The rooted plantlets were successfully acclimatized in vermiculite:sand:soil (1:1:1) potting mixture.     

An investigation on the effect of different plant growth regulating compounds in in vitro shoot tip and node culture of lemon seedlings

The possible application of some less commonly used in vitro growth regulating compounds is outlined. A number of treatments were applied to determine the best way of inducing in vitro shoot proliferation and rooting on a modified Driver–Kuniyuki [HortScience 19 (1984) 507] basal medium of lemon (Citrus limon (L.) Burm, f. cv. Interdonato) seedlings. 6-Benzyladenine (BA) alone (1, 2 and 4 mg l⁻¹) and in combination with either orange juice (10%, v/v), silver nitrate (3 mg l⁻¹), gibberellic acid (GA₃) (0.1 mg l⁻¹ at the establishment stage and 0.5 mg l⁻¹ at all combinations during the proliferation stage) or abscisic acid (ABA) (0.2 mg l⁻¹ only at the establishment stage) were used to stimulate shoot formation during the establishment and the proliferation stage. The combination of BA with ABA gave a high rate of shoot formation, while GA₃ and silver nitrate enhanced shoot elongation. When these shoots were transferred to the rooting stage, the effect of application of two different auxins (indole-3-butyric acid (IBA) and α-napthaleneacetic acid) was examined, as well as different methods of application (auxin added to the basal medium and auxin application by dipping the base of the explant in auxin solution). Dipping the base of the explants in a 50% ethanol solution of IBA at 1000 mg l⁻¹ for 5 s resulted in 80% rooting with subsequent 90% survival of these explants, during acclimatization under mist.     

Prohexadione–Ca inhibits vegetative growth of ‘Smoothee Golden Delicious’ apple trees

Experiments to test the effectiveness of prohexadione–Ca as a growth inhibitor in apple trees have been carried out for 3 years in the Middle Ebro Valley (Spain). Also, effects on fruit quality and flower initiation were evaluated. The application of 100–400 mg l⁻¹ of prohexadione–Ca between 12 and 30 days after full bloom (DAFB) to ‘Smoothee Golden Delicious’/M9 apple trees resulted in the inhibition of shoot growth, the effect increasing with concentration, and a greater inhibition was obtained when the trees were first sprayed 12–20 DAFB. A second spray was usually needed to avoid a regrowth of the shoots. The effectiveness of the second application was related to the concentration applied and the date of the first spray. The relative increase in trunk-cross-sectional area was not affected by the growth inhibitor. No negative effects on yield and fruit quality were found except for a reduction of soluble solid content. Flower initiation in the following year was not affected. Concentrations of 100–200 mg l⁻¹ applied shortly after full bloom should be recommended, bearing in mind that a second application might be necessary 6–8 weeks later.     

Arsenic as a factor affecting virus infection in tomato plants: changes in plant growth,peroxidase activity and chloroplast pigments

The influence of arsenic and Cucumber mosaic virus (CMV), applied separately and simultaneously on young tomato plants was studied. The plants were cultivated in containers under glasshouse conditions. Four main variants were arranged. The first one was without additional As pollution of soil, named as a control, and the other three variants, with As added at 25, 50 and 100 mg kg⁻¹ to dry soil respectively. Half of the plants in each experimental container were inoculated with CMV and the rest uninoculated. A clear response in plant behavior under the conditions of biotic and abiotic stress was estimated. Both arsenic and virus infection had a negative effect on tomato plants by limiting the growth of their roots and above growth parts. The changes in roots were more significant than of stems. Virus infection was a stronger stress factor than arsenic applied at levels of 25 and 50 mg kg⁻¹. The effect of each stress factor applied separately was enhanced in cases of their simultaneous application. The strongest negative effect was manifested in the infected plants, treated with excess arsenic of 100 mg kg⁻¹. It was established that the infection, caused by CMV in tomatoes, was affected by the presence of arsenic in the soil and concentration of the latter. Doses of 25 and 50 mg kg⁻¹ were favorable for infection development, while the dose of 100 mg kg⁻¹ was an inhibitor.Virus infection induced stronger specific peroxidase activity (SPOA) than As treatment. The combination of both stress factors reduced the positive peroxidase response caused by virus infection. Arsenic at rate 50 and 100 mg kg⁻¹, virus infection and the combination of both stress factors at 25 mg kg⁻¹ reduced chlorophyll a, chlorophyll b and carotenoid content The virus infection in cases of the higher arsenic doses reduced the As effect. There was an interaction between the two effects of biotic and abiotic stress. When arsenic and virus infection were applied simultaneously, they caused modification of the effect of each stress on the plants, when applied separately.     

The effect of mycorrhizal symbiosis on the development of micropropagated artichokes

In this work, microrosettes of Cynara cardunculus L. var. scolymus Fiori of the “catanese” type were subcultured in a medium supplemented with 6-benzylaminopurine (BAP) (0.05 mg l⁻¹). For root induction, indoleacetic acid (IAA), α-naphthalene acetic acid (NAA) and indole-3-butyrric acid (IBA) were used at three concentrations: 2, 5 and 10 mg l⁻¹. The highest percentage of rooted shoots was aided by the presence of 10 mg l⁻¹ IAA.Once transplanted in pots, the plantlets were inoculated with 10 g Glomus viscosum strain A6 (AM fungus). Acclimatisation was clearly facilitated by the addition of the AM fungus. Indeed, the mycorrhizal plantlets registered a survival of between 90 and 95% for the rooting shoots and 60% for the non-rooting shoots.The botanical characterization of the material produced was carried out in field and was based on several morphological and productive parameters. Data collected confirm the characteristics of the original cultivar, the efficiency of the in vitro propagation material and the possibility of using this technique in early types of artichoke.     

Micropropagation of Vitis thunbergii Sieb. et Zucc., a medicinal herb,through high-frequency shoot tip culture

This study describes a protocol for rapid and large-scale in vitro propagation of the valuable medicinal herb Vitis thunbergii Sieb. et Zucc.. Culture conditions influencing shoot proliferation and rooting of the two clones (three- and five-lobed) were examined. Three medium formulations, Murashige-Skoog (MS), Woody Plant Medium (WPM) and Nitsch and Nitsch (NN) medium, were tested for growth of shoot tip culture, and WPM was found to have a superior proliferation rate. The chlorophyll content of leaves was highest in those cultured on NN, followed by those on MS and WPM medium. WPM medium supplemented with 0.5 mg l⁻¹ 6-benzyladenine (BA) displayed the highest proliferation rate (15–19 nodes or 3–4 shoots per explant). The rooting was optimized using MS medium supplemented with 0.5 mg l⁻¹ napthaleneacetic (NAA) with eight roots, 3 cm long after 1 month of culture. High frequency callus formation was observed in the basal end of explants cultured on NAA-containing medium. Following acclimatization, rooting plantlets were transferred to the plastic house with a 95% survival rate.     

Factors controlling high efficiency adventitious bud formation and plant regeneration from in vitro leaf explants of roses (Rosa hybrida L.)

Studies were conducted to improve adventitious bud regeneration in roses (Rosa hybrida L.), specifically to extend the protocol to different genotypes and to initiate production of multiple shoots per explant. The best results were obtained by using a two-stage procedure where excised leaflets were incubated on Murashige and Skoog (MS) (1962) induction medium with 6.8 μM TDZ plus 0.49 μM IBA in the dark for 7 days and subsequently transferred to an MS-based regeneration medium with 2.22 μM BA plus 0.049 μM IBA exposed to a PPFD of 15 μmol m⁻² s⁻¹ PAR. Bud formation capacity was also significantly affected by the genotype and the environment, such as the use of bottom cooling creating a lower RH in the vessel. The addition of silver nitrate to the induction medium also significantly improved the percentage of regeneration in three genotypes tested. Regenerated shoots failed to elongate when transferred to MS proliferation medium containing 0.5 mg l⁻¹ BA, however maximum bud development and elongation were achieved when kinetin in the range 1–2 mg l⁻¹ was used. Elongated shoots were excised and rooted best on zero growth regulator half-strength MS modified medium. Rooted plantlets were acclimatized under greenhouse conditions for evaluation of somaclonal variation.     

Video evaluation of ethylene sensitivity after anthesis in carnation (Dianthus caryophyllus L.) flowers

Differences in ethylene sensitivity among carnation (Dianthus caryophyllus L.) cultivars were evaluated using a time-lapse video recording system. Measurement of time to petal inrolling of ‘White Sim’, ‘Nora’, ‘Chinera’, and line 64-54 flowers subjected to a range of 1–20 μl l⁻¹ ethylene showed that 10 μl l⁻¹ was the optimum concentration for sensitivity evaluation with our video system. With this system we found clear differences in ethylene sensitivity among 10 cultivars and one line. ‘Candy’, ‘Pallas’, ‘Chinera’, and line 64-54 had lower ethylene sensitivities than the other seven cultivars. Line 64-54 had the longest ethylene response time (20.6 h to start of petal inrolling). Video monitoring is a simple and accurate way of evaluating ethylene sensitivity. We have also used the system to study changes in the ethylene sensitivity of carnation flowers after anthesis. We were able to detect a shift in responsiveness to ethylene that was impossible to detect by previous methods. In the Sim-type carnation cultivars tested (‘White Sim’, ‘Scania’, ‘U Conn Sim’, and ‘Nora’), ethylene sensitivity after anthesis decreased significantly with age in both early-cut and late-cut flowers. These results clearly showed that decline of ethylene sensitivity is caused by the increasing physiological age of flowers. Ethylene sensitivity after anthesis decreased with age in normal Sim-type carnations in the same way as in long-vase-life variants such as ‘Sandrosa’.     

Seasonal changes in CO2 assimilation in leaves of five major Greek olive cultivars

Leaf CO₂ assimilation rate, stomatal conductance (g_s), internal CO₂ concentration (C_i), chlorophyll (a + b) content, specific leaf weight (SLW) and stomatal density were measured during the season, under field conditions, for five major Greek olive cultivars, ‘Koroneiki’, ‘Megaritiki’, ‘Konservolia’, ‘Lianolia Kerkiras’, and ‘Kalamon’, with different morphological and agronomic characteristics and diverse genetic background. Measurements were taken from current-season and 1-year-old leaves, and from fruiting and vegetative shoots, throughout the season, from March to November in years 2001 and 2002. CO₂ assimilation rates showed a substantial seasonal variation, similar in all cultivars, with higher values during spring and autumn and lower values during summer and late autumn. Stomatal conductance (g_s) followed similar trends to leaf CO₂ assimilation rates, increasing from March to July, following by a decrease during August and increasing again in autumn. ‘Koroneiki’ had the highest leaf CO₂ assimilation rate and g_s values (21 μmol m⁻² s⁻¹ and 0.45 mol m⁻² s⁻¹, respectively) while ‘Lianolia Kerkiras’ and ‘Kalamon’ showed the lowest leaf CO₂ assimilation rate and g_s values (13–14 μmol m⁻² s⁻¹ and 0.22 mol m⁻² s⁻¹, respectively). One-year-old leaves had significantly higher leaf CO₂ assimilation rate than current-season leaves from April to June, for all cultivars. From August and then, leaf CO₂ assimilation rate in current-season leaves was higher than in 1-year-old leaves. There were no significant differences in leaf CO₂ assimilation rate between fruiting and vegetative shoots. Total chlorophyll (a + b) content increased with leaf age in current-season leaves. In 1-year-old leaves chlorophyll content increased in spring, then started to decrease and increased slightly again late in the season. Chlorophyll content was higher in 1-year-old leaves than in current-season leaves throughout the season. Total specific leaf weight (SLW) increased throughout the season for all cultivars. Stomatal density in lower leaf surface was lowest for ‘Koroneiki’ (399 mm⁻²) and highest for ‘Megaritiki’ (550 mm⁻²). Our results showed differences in leaf CO₂ assimilation rate among the five different olive cultivars, with a diverse genetic background, ranging from 12 to 21 μmol m⁻² s⁻¹. From the five cultivars examined, ‘Koroneiki’, a drought resistant cultivar, performed better and was able to maintain higher leaf CO₂ assimilation rate, even under high air vapor pressure deficit. All cultivars had a pronounced seasonal variation in leaf CO₂ assimilation rate, affected by date of the year, depending on ambient conditions. The high temperatures and high air vapor pressure deficit occurring during summer caused a reduction in leaf CO₂ assimilation rate in all cultivars. Leaf CO₂ assimilation rate was also affected by leaf age for all cultivars, with old leaves having significantly higher leaf CO₂ assimilation rate than young leaves early in the season.     

Fruit set,seed development and embryo germination in interploid crosses of citrus

Interploid crosses of diploid Kinnow mandarin, Succari sweet orange and Sweet lime with tetraploid Kinnow were made reciprocally for the production of triploid plants. Low fruit set and occurrence of underdeveloped or empty seeds was common in all interploid crosses. The hybrid fruits harvested after 12–14 weeks or 7 months after pollination produced many underdeveloped and few developed seeds; however, tetraploid Kinnow as seed parent yielded more developed seeds per fruit. The under developed seeds were devoid of endosperm. Nucellar embryony was higher in the diploid than in the tetraploid strain of Kinnow. Immature embryos of seeds harvested 12–14 weeks after pollination were cultured in vitro on MS media supplemented with adenine sulphate (20 mg l⁻¹) and malt extract (500 mg l⁻¹). Maximum germination (75%) of hybrid embryos from underdeveloped seeds was obtained in 4× × 2× cross of Kinnow strains. The germinated plantlets were transferred into pots and noted 59–89.3% survival rate in various crosses.