Growing season and hydrogen peroxide effects on root induction and development in Olea europaea L. (cvs ‘Frantoio’ and ‘Gentile di Larino’) cuttings

Semi-hardwood cuttings of ‘Frantoio’ (high rooting ability) and ‘Gentile di Larino’ (low rooting ability) cultivars were obtained from 1-year-old olive shoots sampled in mid-August during the 2000 and 2001 growing season. Semi-hardwood cuttings were dipped in IBA 4000 ppm and H₂O₂ (0%-control or 3.5% w/v) solutions before rooting in greenhouse equipped with an automatic mist system. At 57 and 88 days after the beginning of rooting treatments cuttings were scored for the presence of callus, roots and roots number. In both cultivars and years, the IBA 4000+H₂O₂ treatment significantly modified rooting of cuttings at 57 days in comparison with IBA 4000 treatment. The positive effects of H₂O₂ on rooting were gradually smoothed after 88 days. At the end of the propagation cycle (88th days), cuttings treated with IBA 4000+H₂O₂ had significantly higher root number in comparison with those treated with IBA 4000 alone.     

Callus induction and plant regeneration from cotyledonary explants of ash gourd (Benincasa hispida L.)

A protocol for the production of complete plantlets through multiple shoots from the cotyledon-derived calli of ash gourd (Benincasa hispida L.) is described. The embryos were excised from mature seeds and cultured on Murashige and Skoog (MS) medium supplemented with 6-benzylaminopurin (BAP, 1–5 μM). After 10 days the well-developed green cotyledons from the growing embryos were isolated and cultured on MS medium fortified with 2,4-D (1–6 μM). The cultured cotyledons gave rise to luxuriantly growing calli after 6 weeks. These calli were subcultured on MS medium supplemented with various concentrations of BAP (1–6 μM) alone or in combination with naphthalene acetic acid (NAA, 0.2 and 0.5 μM) for regeneration. The regenerated shoots were multiplied and rooted on quarter strength MS medium supplemented with indole-3-butyric acid or NAA (1–5 μM). The rooted shoots were transplanted to soil with 90% success.     

Auxins increase the occurrence of leaf-colour variants in Caladium regenerated from leaf explants

Leaf explants of Caladium ‘Pink Cloud’ were cultured in vitro on MS medium containing various auxins (NAA, IBA, IAA, 2,4,5-T and 2,4-D) in combination with cytokinin (BA). NAA gave the most vigorous in vitro propagation of this plant, and only 15% of the plants were leaf-colour variants on the medium containing 0.5 μmol NAA. Leaf colour variation was observed in all plants regenerated on the medium containing 2,4-D at 0.5–4.5 μmol. In hormone-free medium, only a few leaf-colour variants (6%) occurred, but the rate of plant regeneration was very low. Application of 0.5 μmol NAA together with 4.5 μmol BA seemed to be the most appropriate for in vitro propagation of Caladium ‘Pink Cloud’ with only a few leaf-colour variants.     

Influence of medium composition and vessel ventilation on in vitro propagation of Phillyrea latifolia L.

Micropropagation of Phillyrea latifolia L. a wild species present in Mediterranean coastal areas having drought and salt tolerance was performed using explants from adult plants. Shoots were induced from nodal explants on the Rugini’s initial medium (IM). Then these were proliferated on either Rugini olive medium (OM) or Linsmaier and Skoog (LS) medium, each supplemented with 2.22 μM 6-benzylaminopurine (BA) or 4.56 μM zeatin (Z). Rooting (66.1±11%) was induced on shoots grown in perlite soaked with half-strength Rugini olive proliferation medium (OMr) containing 2.69 μM α-naphthaleneacetic acid (NAA) and 160 mg l⁻¹ putrescine. Both shoot multiplication and rooting were performed using Magenta^® GA-7 (Sigma) vessels either non-permeable or permeable to gas exchanges. Contamination (about 40%) was observed during the first five passages notwithstanding the addition of cefotaxime to the culture medium, but a high proliferation rate (90%) of explants provided enough healthy plant material. The highest shoot proliferation was observed on LS medium and zeatin whereas the presence of the ventilated filters reduced fresh weight of explants growing on LS media and did not affect shoot growth on OM media. During rooting, the use of ventilated vessels in comparison with the closed ones enhanced development of roots, and doubled the dry weight of plantlets. The vessel ventilation combined with the artificial substrate (perlite) was beneficial for in vitro acclimatization of rooted Phillyrea plantlets.     

Micropropagation and accumulation of essential oils in wild sage (Salvia fruticosa Mill.)

A protocol for in vitro propagation of the wild three-lobed sage (Salvia fruticosa Mill.) (Synonym, Salvia triloba L.) was developed. Shoot tips were excised from in vitro seedlings and established on MS, Nitch and Nitch (NN), or B5 medium. For shoot proliferation, in vitro nodal and apical explants were cultured on MS medium containing 0.25–2 μM 6-benzylaminopurine (BA), 6-furfurylaminopurine (kinetin), or thidiazuron (TDZ). Proliferated microshoots were rooted on MS medium supplemented with 2.7–11.4 μM indole-3-butyric acid (IBA), indole-3-acetic acid (IAA), or α-naphthaleneacetic acid (NAA). Results indicated that shoots established at 100% regardless of media type, however, shoot height, nodes per shoot, and leaf number were highest for explants established on MS medium compared to NN or B5. Number and height of proliferated shoots, nodes per shoot, and leaf number were highest for nodal explants cultured on a medium containing 0.75 μM BA. Microshoots cultured on a medium supplemented with 2.7 μM IBA exhibited the highest rooting percentage compared to those cultured with IAA or NAA. Essential oil composition in microshoots and shoots of greenhouse-grown plants was determined by gas chromatography/mass spectrometry. The major essential oils detected in both plant materials were α-pinene, 1,8-cineole, camphor, and borneol. No α-thujone or β-thujone was detected. The content of essential oils, camphor, and borneol were higher in the microshoots than in shoots of greenhouse-grown plants.     

Assessment of clonal genetic variability in Olea europaea L. ‘Cobrançosa’ by molecular markers

Olive tree is mainly vegetatively propagated; therefore a small level of polymorphism is expected among clones of the same cultivar. In order to access the level of intra-varietal genetic variability within a collection of 120 clones of the Portuguese olive ‘Cobrançosa’ DNA fingerprinting was performed. Ten random amplified polymorphism DNA (RAPD) primers amplified 150 fragments, of which 75 were polymorphic, while 10 inter-simple sequence repeats (ISSR) primers amplified 179 fragments of which 98 were polymorphic. ‘Cobrançosa’ clones were compared and analysed using Jaccard's coefficient with unweighted pair group mathematical averages, using the RAPD data, the ISSR data and both markers simultaneously. The data indicates a wide intra-varietal genetic variability among the clones. It was possible to cluster some clones according to geographical provenance. Analysis of molecular variance revealed greater variation within clones than among different geographical origins. Significant genetic diversity among the ‘Cobrançosa’ olive cultivar, even though the clones came from a limited geographical area, was also detected.     

Flowering and fruiting in ‘Patterson’ apricot (Prunus armeniaca) in response to postharvest application of gibberellic acid

In July or August of 1988 and 1989 which was approximately 2 or 6 weeks, respectively, after fruit harvest, cultivar ‘Patterson’ apricot (Prunus armeniaca) trees were sprayed with a single spray of either 10, 50 or 100 p.p.m. gibberellic acid (gibberellin A₃, GA). GA sprays of 100 p.p.m. applied in early July reduced flower number per centimeter of limb length in the year following treatment. Flower number per centimeter of limb circumference was reduced by sprays of 50 and 100 p.p.m. GA applied in July. Fruit set was not affected by GA sprays. The yield and fruit number of hand thinned trees was equivalent to that found on trees treated with 50 and 100 p.p.m. GA sprays in July. Individual fruit weight (size) was increased by GA sprays of 50 and 100 p.p.m. in July compared to hand thinned trees. Fruit maturity was advanced when yields were reduced by GA sprays. In July, GA sprays of 10 p.p.m. resulted in increased individual fruit weight without reduced total yields per tree compared to non-thinned control trees. Results showed that the use of GA sprays the year before flowering (July) decreased flower numbers, eliminating the need for chemical or hand fruit thinning of ‘Patterson’ apricot.     

Use of branch cross-sectional area for predicting pruning dose in young field-grown Quercus virginiana ‘Cathedral’ in Florida, US

Allometric relationships for trunk, first order branches and associated foliage were developed to develop a repeatable pruning dose for wind interception studies on Quercus virginiana Mill ‘Cathedral’. Three trees were dissected to develop relationships. It was determined that leaf mass was linearly related to the basal area of the primary branch, consistent with pipe model expectations. A pruning dose for leaf mass removal was defined by tracking basal branch areas and removing entire first order branches. Leaf mass was closely related to leaf surface area, however leaf mass varied with compass orientation while leaf area remained unchanged. The use of wood cross-section area conservation rules for branching in Lindenmayer (L-system) computer modeling is shown to be inconsistent with the data set, as is often observed in the field. The area conservation assumption is made to force taper into computer models, and departures are accepted by assuming heartwood formation forces imbalance into the model. The data set was developed from 3 year old or younger wood. The species is known to retain viable vessel elements in sapwood for at least 3 years in the areas surrounding the testing site. Since it is doubtful that there was heartwood or non-functional sapwood in the test trees, use of the area balance assumption for modeling by asserting heartwood influence is questionable.     

Effects of N–P–K deficiency and temperature regime on the growth and development of Lilium longiflorum ‘Nellie White’ during bulb production under phytotron conditions

One-year-old scale bulblets of Lilium longiflorum Thunb. ‘Nellie White’ (Easter lily) were grown under a combination of six constant day/night temperature regimes and five N–P–K nutrient treatments under short days for 107 d (growing period 1 or GP-1) to compare the effects on growth and development and bulb production. Results during GP-1 were as follows: failure of bulblets to produce a shoot (“no-shows”) was found at high temperatures (30/26 and 26/22 °C) and not influenced by the nutrient treatments. Flower bud abortion was observed in the minus-N, minus-P, and minus-N–P–K treatments at high temperatures (30/26 or 26/22 °C), but not observed at any temperatures in the complete and minus-K treatments. The loss of bulb fresh weight in minus-N treated bulblets was less than in the other treatments resulting in less root and shoot growth in the minus-N treatment. At the intermediate temperatures where growth was highest, omission of N, P, K, or all three resulted in losses in stem bulb fresh weight, stem plus leaf fresh weight, number of flowers, and stem root fresh weight. Omission of N, P, or all three nutrients resulted in lowest basal root fresh weight. Bulb N and K concentrations were lowest in plants grown with complete nutrient solution at the two coldest temperature regimes (14/10 and 10/6 °C). Bulb P concentration was lowest at the three coldest (18/14, 14/10 and 10/6 °C) and the warmest (30/26 °C) temperature regimes. Stem length was shorter when P was omitted. Omission of any of the three nutrients resulted in lower concentrations of the other nutrients. The one exception was where low K did not affect N concentration. In the second phase of the experiment, plants grown at 18/14 °C and irrigated with the complete nutrient solution for 107 d (GP-1) were continued at this day/night temperature regime and five N–P–K nutrient treatments for another 89 d under long days (growing period 2 or GP-2). Results during GP-2 were as follows. Basal bulb yield was not impacted by omission of N, P, or K, or all three. Of all growth measurements, only stem plus leaf fresh weight was lower and only when all three nutrients (minus-N–P–K) were omitted. At the end of GP-2, basal bulb concentrations of N and P did not differ from the concentrations in bulbs at the beginning of GP-1; however, K concentration was lower at the end of GP-2. Omission of N or P further resulted in lower bulb K concentration, suggesting that a moderate supply of N, P, and K be applied during GP-2 since an additional year of bulb production is needed to produce forcing-sized bulbs.     

Effects of thermoperiodicity and plant population density on stem and flower elongation, leaf development, and specific fresh weight in single stemmed rose (Rosa hybrida L.) plants

Thermoperiodicity, i.e. growth in the alternating temperature regime with the same diurnal mean compared with growth at the constant temperature at which optimal growth occurs, was studied at three plant population densities in four cultivars of Rosa hybrida L. Single-node cuttings with five-leaflet leaves were excised and grown as single-stemmed rose plants at an average photosynthetic photon flux density of about 260 μmol m⁻² s⁻¹ and supplied with carbon dioxide at about 1000 μmol mol⁻¹. The optimal constant temperature regime was 22 °C day (20 h)/22 °C night (4 h); alternating temperatures were 23 °C day (20 h)/18 °C night (4 h). The plant population densities were 100, 131 and 178 plants m⁻² of bench area. Thermoperiodicity was absent, or could not be detected, in the parameters related to the growth period, the formation of fresh biomass, the bloom quality, and most parameters related to shoot elongation. However, classic thermoperiodic effects of alternating regime were significant in the cultivars Red Velvet and Sonia, with shoot elongation promoted (7.1 and 10.5%, respectively) in the growth phase from onset of axillary bud growth until the flower bud became visible. Compared with the other two cultivars, plants of Red Velvet and Sonia tended to develop longer internodes. The results, obtained concurrently at three different plant population densities, suggest that thermoperiodicity can affect (single-stemmed) plant growth and development in R. hybrida. Increased plant population density also increased plant height at visible flower bud, but the bloom quality, expressed as specific fresh weight, and the flower height at anthesis was decreased at the highest density. Increased plant population density increased the number of five-leaflet leaves developed in Red Velvet, but had no effect on leaf number in Texas and Sonia, while, in Lambada the leaf number was decreased at the highest density.     

Temporal dynamics of nutrient and carbohydrate distribution during crop cycles of Rosa spp. ‘Kardinal’ in response to light availability

Rose plants that are flush harvested exhibit episodic growth patterns. During these crop cycles little biomass accumulation occurs immediately following harvest; and as new shoots emerge a period of rapid shoot growth and biomass accumulation occurs. The temporal changes in whole-plant nutrient and carbohydrate distribution during these crop cycles and the role of storage in new shoot growth are not well documented. The objective of this project was to quantify N, P, K, and total non-structural carbohydrates (TNC) distribution in roots, base stems, base leaves, and new shoots during crop cycles in response to light availability. Plants were grown in solution culture under high or low light (mean daily light integral 45.3 or 13.1 mol m⁻² d⁻¹, respectively) during 30–35 day crop cycles. Every five days destructive sampling was used to determine biomass and N, P, K, and TNC concentration of rose plant compartments. N and TNC accumulated in base plant compartments during the first ten days of the crop cycles. N, P, K, and TNC in base plant compartments declined during days 10–25 during a crop cycle concurrent with the rapid growth of flower shoots. N, P, and K storage in base plant parts represents 27, 22, and 24% of the potential N, P, and K required by flower shoots under high light; and 19, 21, and 22% of requirements under low light. TNC storage in base plant parts represents 4–10% of the final biomass of flower shoots. Mobilization of N, P, K, and TNC stored from base plant parts appears to be important during the stage of rapid flower shoot growth when absorption by roots or photosynthesis by shoots was insufficient to meet flower shoot demands. Plant carbohydrate status was improved under high light conditions; storage of N and TNC declined under low light.     

Free amino acids as indicators of little leaf in zinc deficiency in the pistachio (Pistacia vera L. cultivar ‘Kerman’)

Zinc deficiency of commercial pistachio trees is characterized visually as ‘little leaf’, analytically by low levels of zinc, and internally by increases in N, P and total soluble N. Under a range of zinc deficiencies, blocks in metabolism arise which lead to the accumulation of free arginine N. Over the growing season, arginine N in healthy leaves is normally used for amino acid and protein synthesis. The physiological states induced by zinc deficiencies reversibly alter the internal correlations among free amino acid components of the soluble N pool. Several correlations are rigidly maintained over the growth and developmental age of leaves, so as to support the visual indices for zinc deficiency.     

Changes in dietary fibre, polygalacturonase, cellulase of navel orange (Citrus sinensis (L.) Osbeck ‘Cara Cara’) fruits under different storage conditions

The consumption of dietary fibre plays an important role in the prevention of diseases, such as constipation, haemorrhoids. Recently, chemical and physical properties of citrus fibres have been widely studied. In this paper, the polygalacturonase (PG) and cellulase (Cx) gene expression of Cara Cara (Citrus sinensis (L.) Osbeck) navel orange fruit stored on tree (ST) was compared with fruit stored in room (SR). The results showed that the mRNA expression levels of PG increased significantly in the fruits of ST, in contrast, the expression levels of Cx increased slightly only in peel of ST. Total pectin (TP) and protopectin of ST fruits pulp were higher than those of SR at every time point. The contents of insoluble dietary fibre (IDF), hemicellulose (HC), cellulose (CEL) and lignin of ST fruits were less than that in SR. However, in fruits from ST, a significant increase of soluble dietary fibre (SDF) and water soluble pectin (WSP) occurred, compared with fruits of SR. Our studies indicated that fruit stored on tree is quite useful for regulating the gene expression and controlling contents of dietary fibre on Cara Cara navel orange.     

Morphogenic gradients of adventitious bud and shoot regeneration in epicotyl explants of Citrus

The in vitro responses of epicotyl explants from ‘Cravo’ rangpur lime (Citrus limonia Osb.), ‘Foster’ grapefruit (C. paradisi Macf.), and ‘Pera’ sweet orange (C. sinensis (L.) Osb.) were characterized for the first time. Further analysis was performed in ‘Cravo’ rangpur lime and ‘Foster’ grapefruit aiming to verify the in vitro morphogenesis of five distinct regions of the epicotyl under different treatments. It was observed the same general pattern of morphogenic gradient along the epicotyl axis in both citrus cultivars, with greater organogenic response as the distance of the explants from the cotyledonary node increased. This morphogenic gradient was influenced by factors related to plant material, composition of the culture medium, and conditions of incubation. The regions of the epicotyl farthest from cotyledons could be used as a source of explants in experiments of genetic transformation of the genotypes evaluated aiming to improve the efficiency of production of transgenic Citrus plants.     

The inhibition of flower bud differentiation in ‘Crimson Gold’ nectarine with GA3 as an alternative to hand thinning

The reduction of flower bud density by gibberellin sprays, to adjust the cropping level, is a novel approach to fruit thinning of peach and nectarine. A linear reduction in the number of flowers developed per unit of shoot length was found following the spray application of increasing concentrations of GA₃, in the nectarine cultivar ‘Crimson Gold’. These reductions in flower number led to reductions in yield at harvest, and increases in mean fruit weight. Flowering was slightly delayed by the GA₃ treatments, but no differences in ripening were detected at harvest, this depending rather on fruit size. The yield obtained by the application of 200 mg l⁻¹ GA₃ corresponded to that obtained with a very good thinning level, as established by hand thinning. No secondary effects on vegetative growth followed either the application of GA₃ or the reductions in crop load by means of hand thinning. Decreasing crop-loads have resulted in an increase in fruit size and an advance of fruit ripening, measured by greater levels of soluble solids and lower flesh firmness. A good commercial quality fruit size was obtained for crop-loads of 300 fruits per tree or less.     

A comparative study of young ‘Thompson Seedless’ grapevines (Vitis vinifera L.) under drip and furrow irrigation. II. Growth, water use efficiency and nitrogen partitioning

The response of 3-year-old grapevines (Vitis vinifera L. cultivar ‘Thompson Seedless’) to furrow and drip irrigation was quantified in terms of water status, growth, and water use efficiency (WUE). Drip irrigation was applied daily according to best estimates of vineyard evapotranspiration while furrow irrigations were applied when 50% of the plant available soilwater content had been depleted. Drip and furrow irrigated vines showed similar water status (midday leaf water potential, Ψ₁) and shoot growth patterns throughout the season. Dry weight partitioning was not significantly different between treatments but root mass was somewhat larger for the furrow than drip irrigated vines. Nitrogen concentrations of the fruit and roots were significantly (P < 0.05) less for the drip irrigated vines when compared with the furrow treatment. Similar WUE (kg water kg⁻¹ fresh fruit wt.) were obtained for both treatments indicating that furrow irrigation was as efficient as drip irrigation under the conditions of this study. The data indicate that drip irrigation may increase the potential for control of vine growth by making vines more dependent on irrigation and N fertilization than furrow irrigation.     

A chilling-insensitive stage in germination of a low-temperature-adapted radish, rat’s tail radish (Raphanus sativus L.) cv. “Pakki-hood”

The rat’s tail radish (Raphanus sativus cv. “Pakki-hood”), cultivated in the northern part of Thailand, does not require low temperature for flower-bud initiation and shows high germinability even at low temperature. To analyze its characteristic temperature response, seedlings were subjected to a 3 day-chilling treatment at 0°C after a series of incubations for germination at 26°C which ranged from 3 h to 4 days. The chilling treatment after an initial stage (3 h to less than 2 days) of incubation at 26°C did not significantly affect the hypocotyl regrowth, but the same treatment after a more than 2-day incubation at 26°C reduced subsequent hypocotyl growth of plants. 1-aminocyclopropane-1-carboxylic acid (ACC)-dependent ethylene-forming activity was also reduced by the chilling treatment after 2–4-day incubation at 26°C. Electrolyte leakage from tissues of seedlings in the chilling treatment was increased in proportion to the length of the incubation at 26°C, indicating severe damage of chilling to plasma membranes after a longer incubation. We found a transition of chilling-sensitivity at 2 days in the incubation period for germinating seeds of Pakki-hood. Seedlings of Pakki-hood chilled earlier than the transition are relatively unaffected in their subsequent growth, but the seedlings become sensitive to chilling after the transition.