Rosario Muleo

Photoregulation of growth and branching of plum shoots: Physiological action of two photosystems

SummaryPlum shoot proliferation was investigated in terms of two distinct processes: axillary bud differentiation and axillary shoot development. Results showed that light quality influenced bud differentiation and interacted with apical dominance in determining shoot outgrowth, resulting in a differentiated structure of shoot clusters and type of branching. Results suggested that blue light, acting through its photoreceptor, increased the number of axillary buds differentiated from apical meristem, but did not remove the apical dominance. Red light removed apical dominance, while reducing the formation of axillary buds; both events appeared to be dependent on the putative amount of phytochrome active form, and independent of light photon fluence rate. On the contrary, blue light action appeared to be dependent on photon fluence rate. In addition, apparent blue-red interactions related to photomorphogenic events fit an antagonistic model for branching regulated by light via cryptochrome and phytochrome photoreceptors. Our results show that the dynamics of shoot cluster development is the product of two events: the formation of new axillary buds and their release from apical dominance.

Long-term somatic embryogenesis from immature olive cotyledons

SummaryA method for obtaining whole plants from immature cotyledons via somatic embryogenesis is described. Cultures were initiated by placing cotyledonary tissues at different developmental stages on SH medium supplemented with NAA and 2iP at different concentrations as an embryo induction medium (EIM). Proliferating masses of adventitious embryos were produced by cvs Frangivento, Picholine and Frantoio when transferred to the embryo expression medium (EEM) characterized by the exclusion of growth regulators. ‘Frangivento’ was maintained on EEM for three years without showing any loss of embryogenic potential while cvs Picholine and Frantoio retained their embryogenic capacity for only three subcultures. Optimum conversion into plantlets for ‘Frangivento’ was observed. Plants established in the greenhouse showed normal growth without change in performance. The protocol described makes it possible to maintain long-term embryogenic capacity; this may be particularly advantageous for propagation and biotech...

Effects of light quality on shoot proliferation of Prunus cerasifera in vitro are the result of differential effects on bud induction and apical dominance

SummaryThe morphogenic effect of different light qualities was investigated on in vitro shoot proliferation of Prunus cerasifera (clone Mr.S. 2/5) in relation to apical dominance and node formation. In intact microcuttings, leader stem length was not affected by light quality but blue and white light produced a higher number of nodes, with shorter internodes than red or far-red light or darkness. The proportion of nodes producing outgrowing lateral shoots was higher in red and far-red light than in white, blue or darkness. In decapitated microcuttings apical dominance was fully released in all the light treatments but not in darkness. Taken together the data show that the proliferation rate is a product of bud induction and release from apical dominance which are differentially affected by light quality. The much lower percentage outgrowth in white and blue light as compared with red light indicates a specific effect of blue light acting in the opposite direction to active (far-red light absorbing) form o...

Application of tissue culture on quince rootstock in iron‐limiting conditions 1

Abstract Two quince rootstocks for pear, clones “MA”; and “Ct.S.212”;, were screened under iron (Fe)‐limiting conditions in in vitro culture. The most important objectives of this work were: first, to develop use of the tissue culture technique as a rapid screening methodology for evaluation of Fe efficiency in quince, and second, to identify morphophysiological characters associated with variation in response. Iron content of the MS medium (200 meq FeEDTA) was reduced to 80%, 65%, 50%, 25%, and 15% of standard content in order to induce chlorosis symptoms. Results showed that “Ct.S.212”; presented a higher proliferation rate and greater growth than clone “MA”; in the 15 and 25% Fe treatments, but clear symptoms of chlorosis were observed in both clones at the two lowest Fe concentrations. Parameters of vegetative development commonly used in in vitro culture proved to be difficult to interpret for this type of screening, and further tests will be necessary. In contrast, type and content of chlorophyll we...

Changes in some physiological and biochemical parameters during two subcultures in kiwi (Actinidia deliciosa) callus

Abstract Kiwi ( Actinidia deliciosa ) calli were grown for two successive 45-day subcultures on agarised medium in order to evaluate the metabolic changes occurring during the growth of the callus. At different times (10, 35 and 45 days of each subculture), increase in fresh weight, oxygen uptake rate, levels of inorganic cations (K + , Ca 2+ , Mg 2+ and Na + ) and of some metabolites (sucrose, glucose-6-phosphate, malic acid, amino acids and adenosine phosphates) were measured. After an adaptive growth phase (0–6 days) and a phase of high growth (6–12 days), the callus growth rate decreased sharply and then remained essentially constant up to the 45th day. The parameter listed above changed with time following a similar pattern in the two analysed subcultures. In the first 10 days, most of them increased (in particular, oxygen uptake rate and the energetic status of the cells); the levels of Na + decreased. After the first 10 days, the levels of glucose-6-phosphate (glu-6-P) and of the adenylate pool and the availability of the high-energy phosphate bonds of ATP and ADP decreased and the Na + levels began to increase; in this period, the rate of oxygen uptake increased, but this corresponded to neither increased availability of the high-energy phosphate bonds of ATP and ADP nor increased growth rate. In the last period (35–45 days) the main metabolic parameters dropped, with a large increase in Na + levels. Transfer onto new medium restored, after the adaptive period, the maximum growth and the levels of the parameters listed above. The data show that during the subculture periods of Actinidia deliciosa calli important metabolic changes occur. They are probably linked to a different status of suffering (for reduction of nutrient availability, accumulation of catabolic products, and/or variations in oxygen and CO 2 diffusion) with the activation of metabolic mechanisms of adaptation and repair. These metabolic changes appear not severe enough to inhibit the growth of the calli. The results obtained with Actinidia deliciosa calli are discussed in relation to protocols of selection and micropropagation.

Characterization of salt tolerant plants derived from a Lycopersicon esculentum Mill. somaclone

Summary Plants were regenerated from cotyledon explants of Lycopersicon esculentum Mill., placed on a control medium and on medium added with a glucose derived, non trophic compound: 3-O-methyl-D-glucose, used as an osmotic agent. A preliminary test conducted in vitro , allowed us to identify a somaclone (named C4) which showed three times higher germination rates compared to wild type, in a salt enriched medium. To confirm the tolerance character in vivo and during the different life phases of the plant, young R1 plantlets from this somadone and wild type plantlets, have been tested with increasing concentrations of salt (0, 75, 150, 300 mmol/L sodium chloride). At the end of the treatment, consistent necrosis of leaf and flower organs were evident only in wild type plants. Moreover, we observed a strong drop of leaf turgor in wild type leaves under salt treatment, instead, line C4 plants retaining the turgor. A highest concentration of sodium was detected in leaf tissues in wild type plants, compared to line C4 ones, attesting the capacity of C4 line plants to regulate the amount of this toxic ion in leaves. The synthesis of organic compounds, proline and total amino acids, was lower in line C4 plants. Polymorphic RAPD fragments in C4 line were identified. Taking together all the data, line C4 plants show the ability to tolerate high salinity conditions, compared to wild type, in particular we suggest that these plants are able to regulate differently the amount of sodium in tissues.

Differential exhibition of photoreversible phytochrome in callus from two woody species, Actinidia deliciosa and Olea europaea

Abstract As part of an investigation of the photomorphogenetic control of organogenesis in woody species, the levels of phytochrome in callus tissues of Actinidia deliciosa (kiwi fruit) and Olea europaea (olive) has been studied by in vivo spectrophotometry. Photoreversible signals were detected in Actinidia leaf callus, irrespective of whether it had been grown in red light, far-red light or darkness. In contrast, phytochrome could not be detected in callus generated from Actinidia pith tissues. Analysis of callus derived from olive leaf tissues showed the presence of phytochrome. The results indicate that callus derived from leaf tissues of these two woody plants contains a light stable (Type II) phytochrome. The absence of detectable phytochrome in Actinidia pith callus indicates that biochemical differences in the original tissues are partially retained in the callus derived from them.

Effect of Hyperosmotic 3-O-methyl-D-Glucose in the Medium on Metabolic Parameters in Actinidia deliciosa Callus

Calli of Actinidia deliciosa were cultured on medium with 30 mM sucrose and 0.2 M 3-O-methyl-D-glucose (3-OMG) and their metabolic adaptation to the hyperosmotic condition was studied. 3-OMG concentration in the tissue reached that of the medium. Experiments with labelled 3-O-methyl-D-U-14C]glucose (3-OM[U-14C]G) showed that it was partially metabolised but not oxidised to CO2. In vivo 31P-NMR showed that in 3-OMG-treated calli a phosphorylated compound, with a chemical shift similar to that of monophosphoesters, was accumulated. The 3-OMG-treated calli showed more negative water (Ψw) and osmotic (Ψπ) potentials than the controls. In the following of subcultures an increase in organic and inorganic osmolytes, together with increase in O2 uptake and decrease in ATP/ADP ratio occurred. The data show that, even if 3-OMG can not be considered a classic osmotic agent due to its permeability, it induced metabolic changes similar to those described for osmotic adaptation, suggesting that the adaptations might be due to a physical or metabolic effect of 3-OMG not linked to a difference between Ψπ and Ψw agar