Effects of reduced irradiance on leaf morphology,photosynthetic capacity,and fruit yield in olive (<Emphasis Type="Italic">Olea europaea</Emphasis> L.)

One-year-old olive trees (cv. Koroneiki) were grown in plastic containers of 50 000 cm³ under full daylight and 30, 60, and 90 % shade for two years. The effects of shade on leaf morphology and anatomy, including stomatal density and chloroplast structure, net photosynthetic rate (P _N), stomatal conductance (g _s), and fruit yield were studied. Shade reduced leaf thickness due to the presence of only 1–2 palisade layers and reduced the length of palisade cells and spongy parenchyma. The number of thylakoids in grana as well as in stroma increased as shade increased, while the number of plastoglobuli decreased in proportion to the reduced photosynthetically active radiation (PAR). The higher the level of shade, the lower the stomatal and trichome density, leaf mass per area (ALM), g _s, and P _N. Shade of 30, 60, and 90 % reduced stomatal density by 7, 16, and 27 %, respectively, while the corresponding reduction in P _N was 21, 35, and 67 %. In contrast, chlorophyll a+b per fresh mass, and leaf width, length, and particularly area increased under the same shade levels (by 16, 33, and 81 % in leaf area). P _N reduction was due both to a decrease in PAR and to the morphological changes in leaves. The effect of shade was more severe on fruit yield per tree (32, 67, and 84 %) than on P _N indicating an effect on bud differentiation and fruit set. The olive tree adapts well to shade compared with other fruit trees by a small reduction in stomatal and trichome density, palisade parenchyma, and a significant increase in leaf area.     

Assigning a Role to the Endogenous Phenolic Compounds on Adventitious Root Formation of Olive Stem Cuttings

The objective of this study was to role the effect of phenolic compounds on the rooting potential of leafy cuttings of the recalcitrant to root olive cultivar ‘Kalamata’ and the easy to root ‘Arbequina’. Subsamples of cuttings were taken for analysis before planting (day 0) in the mist system and during the early phases of rhizogenesis (EPR). ‘Kalamata’ presented higher initial (day 0) total phenols in summer and total o-diphenols in autumn and spring compared to ‘Arbequina’, while ‘Arbequina’ had significantly higher initial total flavonoids and flavanols in autumn. A positive correlation was found between initial total phenols and rooting ability of ‘Arbequina’. In ‘Kalamata’ a positive correlation was established between initial total o-diphenols and rooting percentage while total flavonoids were negatively correlated with rooting. Generally, total phenols, o-diphenols, flavanols and flavonoids did not differ between the two cultivars and their concentration reduced significantly 15 days after planting. Furthermore, ‘Arbequina’ presented higher initial tyrosol, chlorogenic acid, luteolin-7-glucoside, rutin, quercetin and luteolin in summer and autumn compared to ‘Kalamata’. The above phenolics were positively correlated with the rooting of ‘Arbequina’. Significant changes were observed in the concentration of the individual phenolics during the EPR, whereas chlorogenic acid, rutin, quercetin and luteolin concentration increased significantly from day 1 to 5. In conclusion, there is a clear relationship between the phenolic profile and adventitious rooting of the two olive cultivars and in fact chlorogenic acid and rutin can be proposed as olive rooting enhancers.

     

The Possible Role of Polyamines to the Recalcitrance of “Kalamata” Olive Leafy Cuttings to Root

The objective of this study was to investigate the role of endogenous polyamines (PAs) (the sum of free plus soluble conjugate plus insoluble bound) on rooting potential of leafy cuttings of an easy, that is,“Arbequina” and a difficult-to-root olive cultivar, that is, “Kalamata”. Subsamples of cuttings were taken for PAs analysis before planting in the mist system and during the early phases of rhizogenesis (EPR). “Arbequina” exhibited higher initial free and total PA content than “Kalamata”. Spermidine (Spd) was the predominant PA observed in both cultivars. A low content of free putrescine (Put) and Spd was found in both cultivars, whereas spermine (Spm) was occasionally detected. “Arbequina” as well as “Kalamata” exhibited the highest free Put and free Spd in summer and Put was the predominant PA among the free PAs. “Arbequina” exhibited the highest individual and total PAs in spring, followed by those in summer and autumn. In contrast, “Kalamata” had the maximum PAs in summer and the lowest in autumn. Changes in the endogenous content of individual and total PAs during the EPR were also observed. Treatment of “Kalamata” cuttings in autumn with both indole-3-butyric acid (IBA) and Put increased rooting compared to IBA alone. Among the PAs administered, Put was the most effective, whereas Spd and Spm failed to promote rooting. PAs, especially in their free form, seem to be involved in the rooting process of olive cuttings; Put application enhanced the rooting response of the difficult-to-root “Kalamata” olive cultivar.     

Stomatal and Chlorophyll Distribution of Cox's Orange Pippin Apple Flowers Relative to Other Cluster Parts

Surface area, chlorophyll concentration and stomatal size anddensity were measured for all green components of floral clusterson Cox's Orange Pippin apple trees to assess their relativepotential for photosynthesis. Before flower opening, sepalsand receptacles had chlorophyll concentrations similar to thosefound in the laminae of rosette leaves. But, whereas the concentrationin rosette leaves continued to increased until fruit set, thosein the sepals and receptacles decreased. Sepals had a greater mature stomatal density than leaf laminaeshortly after bud burst; although both densities increased,that on the laminae later exceeded that on sepals. Flowers contributed significantly to the green surface are (40%),chlorophyll content (30%) and mature stomatal number (25%) offloral clusters at the green cluster stage, but these contributionsthen decreased. Cox apple flowers appear to have the potentialfor contributing significantly to their carbohydrate requirementat a time when the rosette leaves are not thought to be exportersof photosynthate.Copyright 1993, 1999 Academic Press Malus pumila, apples flowers, chlorophyll, stomata, surface area, flower photosynthesis     

Effects of shoot girdling on photosynthetic capacity, leaf carbohydrate, and bud abscission in pistachio (Pistacia vera L.)

The effects of shoot girdling on stomatal conductance (g _s), leaf photosynthesis (P _N), concentrations of carbohydrates, nitrogen and chlorophyll (Chl) in leaves, areal leaf mass (ALM), the diameter and length of shoots, and bud abscission in pistachio were investigated. Girdling individual shoots at the base of the current year’s shoot (girdle I), separating inflorescent buds on the terminal current year’s shoot from the developing fruits on the previous year’s shoot, reduced inflorescent bud abscission by 70% in comparison to nongirdled controls. Girdle I significantly reduced concentrations of nitrogen in leaves but increased those of nonstructural carbohydrates particularly of starch. Shoot diameter increased by 13.1% and 26.4% at 33 and 81 days after girdling (DAG), respectively, compared to 1% and 3.4% in the control, respectively. Both the leaf dry mass/fresh mass ratio and ALM were increased significantly by girdle I from 12 DAG. The concentrations of Chl a, Chl b, Chl (a+b), as well as the ratio of Chl a/b, all decreased with girdle I. The greatest negative effect of girdle I was on g _s and P _N. P _N was reduced by 55% of its initial value and was 44% less than in the control leaves at 10 DAG, and fell to approximately 30% that of the control from 21 DAG. In contrast, girdling at the base of one-year-old shoots (girdle II), thus not separating fruits from the inflorescent buds, did not significantly affect g _s or P _N. The effect of girdling on P _N and the possible factors that are involved in the reduction of photosynthesis in pistachio are discussed.     

The Photosynthetic Activity of Cox's Orange Pippin Apple Flowers in Relation to Fruit Setting

The ability of green parts of Cox's apple flowers (sepals, receptacleand pedicel) to photosynthesise was demonstrated using ¹⁴CO,feed experiments and an infra-red gas analysis (IRGA) system.The sepals had the greatest ability, comparable with that ofleaves, followed by the receptacle. Sepals and leaves fixedthe same amount of CO₂ in the dark. Photosynthesis and respirationrates in orchard flowers were measured in comparison to thoseof leaves. Flower gross photosynthesis (GP) was about a thirdof that of leaves at the balloon stage and 15 d after full bloomin 1987, but this ratio was much less at full bloom (FB) inthe same year. GP in flowers decreased rapidly with fruitletenlargement. It was estimated that flower photosynthesis significantly contributedto their carbohydrate balance (15-33%) during the floweringand fruit setting periods. The highest contributions were made at the green cluster stage(33%) and between 6 and 11 d after FB (27%), the period whenthe fruit set had been initiated. Removal of sepals, the mainphotosynthetic parts of the flower, at the pink bud stage decreasedinitial set. The results suggest that flower photosynthesismight play an important role in flower growth and fruit setting.Copyright1994, 1999 Academic Press Apple, photosynthesis, respiration, fruit setting, flower photosynthesis, sepal removal     

Changes of Respiration Rate, Ethylene Evolution, and Abscisic Acid Content in Developing Inflorescence and Young Fruit of Olive (Olea europaea L. cv. Konservolia)

Simultaneous measurements of respiration, ethylene production, and abscisic acid (ABA) concentrations, as well as the growth parameters length, fresh weight (FW), and dry weight (DW) of olive (Olea europaea L. cv. Konservolia) inflorescence were carried out at short intervals (3–7 days) during the period from bud burst until the 3rd week after full bloom (AFB), when young fruit reached 8 mm in length. The axis of inflorescence elongated remarkably during the 3rd week after bud burst (ABB), massive bract shedding occurred during the 4th week ABB, full bloom (FB) was observed 7 weeks ABB, and massive floral organ abscission 1 week AFB. The results showed a continuous increase in inflorescence FW and DW from bud burst until 4 days before FB. Respiration rate, ethylene production, and levels of ABA were relatively high during the first 3 weeks ABB. After this period, respiration and ethylene followed a similar pattern of changes, inversely to that of ABA concentration. An accumulation of inflorescence ABA 6 and 4 days before FB was associated with the minimum values of respiration and ethylene production on the same dates. The sharp decrease in the ABA concentration during FB and 3 days later was followed by a high rise in ethylene and an increase in respiration rate, which both rose further 1 week AFB. The results suggest a possible correlation of ABA with the early stage of floral abscission, whereas ethylene production seems to be correlated with the terminal separatory activity in olive inflorescence abscission processes. Received May 28, 1998; accepted November 17, 1998