Primo Proietti

Gas Exchange in Olive Fruit

Dry matter (DM) of olive fruit (cv. Leccino) constantly increased from fruit-set (mid-June) to the end of October. The oil content increased rapidly from the beginning of August, about 40-50 d after full bloom (AFB), to the end of October. As the oil content increased, the saccharide content decreased. On a DM basis, fruit dark respiration rate (RD) and stomatal conductance (Gs) were high soon after fruit-set, then strongly decreased. Gross photosynthetic rate (PG) in full sunlight was high in the first 3 weeks after fruit-set, when the chlorophyll (Chl) content and the ratio between fruit surface area and volume were high, then it progressively decreased. The fruit intercellular CO2 concentration (Ci) was always relatively high, particularly from September onwards. The PG increased following the increase of irradiance (I). The daily PG trend was similar to the I and temperature trends, showing the maximum values at 14:00 h. For a large part of the fruit growing period, during daylight, the CO2 intake by a fruit permitted the reassimilation of a large part (40-80%) of the CO2 produced by RD. The stomata in the first stages of fruit growth were oval and surrounded by guard cells, two months later they lost their shape and were covered by wax. The reduction in fruit PG during fruit growth could be connected to the reduction of the ratio between fruit surface area and fruit volume and the cellular differentiation, whereas the constant high Ci seems to exclude the influence of Gs decrease. Even if olive fruit is highly heterotrophic organ, its photosynthesis can considerably reduce the use of assimilates for respiration and favour fruit maintenance and growth.

Effect of irrigation on fruit quality of table olives (Olea europaea), cultivar ‘Ascolana tenera’

Abstract This trial was carried out to study the relationship between irrigation and vegetative and productive activity and fruit quality of table olives (Olea europaea), cultivar ‘Ascolana tenera’. Irrigation every 15 days, with c. 0.4 m3/tree at each irrigation, from the end of June to mid September, induced higher leaf surface area, photosynthesis, and transpiration during the entire growing period compared to the control. This led to an overall positive effect on total production per tree. Fruit weight, volume, and pulp/pit ratio all increased. Water availability influenced cell division more than cell expansion. Fruit shape was not influenced. Irrigation had no substantial delaying effect on ripening. With irrigation, pulp water content increased, and firmness and fruit sugar content decreased slightly, but after preservation in brine, pulp water content, and the sensory characteristics of the olives (flavour, texture, and detachment of the pulp from the pit) from irrigated and non‐irrigated olives w...

A comparative study on the interference of two herbicides in wheat and italian ryegrass and on their antioxidant activities and detoxification rates.

A study was carried out to compare the effects of treating wheat (Triticum aestivum) and Italian ryegrass (Lolium multiflorum) with atrazine and fluorodifen. The herbicides interfered with photosynthesis and dark respiration, depending on the species. Atrazine decreased photosynthesis in both species and dark respiration in wheat, while fluorodifen caused decrements of photosynthetic activity of wheat. Antioxidant enzymes, such as ascorbate peroxidase (APX), dehydroascorbate reductase (DHAR), and glutathione reductase (GR), were generally more active in untreated and treated wheat with respect to Italian ryegrass, which explains why oxidative damage, expressed as malondialdehyde (MDA) content, was only found in ryegrass. Investigations on the activity of herbicide-detoxifying enzyme, glutathione S-transferase (GST), and on the accumulation and persistence of the herbicides in the plants showed higher detoxification rates in wheat than in the grass.

Effects of leaf to fruit ratios on fruit growth in chestnut.

In Castanea sativa Mill. cv. Santa Restituta, 10 days after full bloom, defoliation to give leaf-to-husk ratios of 2/1, 4/1, 7/1, 10/1 and 14/1 was performed on both girdled and ungirdled shoots fully exposed to the sun. The results showed that assimilates can be easily translocated and it is necessary to have about 10 leaves well exposed to light per husk (about five leaves per fruit) to ensure normal fruit development. Fruit is a stronger sink than shoot reserve tissues. A feedback inhibition of photosynthesis at high leaf-to-husk ratios is suggested.

Photosynthetic behavior of Spanish Arbequina and Italian Maurino olive (Olea europaea L.) cultivars under super-intensive grove conditions

The study was carried out in a four-year-old super-high density olive grove in Central Italy to compare leaf gas exchanges of Spanish Arbequina and Italian Maurino olive cultivars. Overall, from mid July to mid November, Maurino had a slightly higher maximum light-saturated net photosynthetic rate (PNmax) than Arbequina. The lowest and the highest PNmax values were recorded at the end of July and in mid November, respectively. Current-season leaves showed similar or slightly higher PNmax values than one-year-old leaves. During the day Maurino always had slightly higher values or values similar to Arbequina, with the highest PNmax being in the morning. Maurino had similar or higher dark respiration rate (RD) values compared to Arbequina. During the day, in both cultivars the RD was lower at 9:00 than in the afternoon. The pattern of the photosynthetic irradiance-response curve was similar in the two genotypes, but the apparent quantum yield (YQ) was higher in Maurino. In both cultivars intercellular CO2 concentration (Ci) tended to increase when PNmax decreased. The increase in Ci corresponded to a decrease in stomatal conductance (gs). The transpiration rate (E) increased from mid July to the beginning of August, then decreased in September and increased again in November. Particularly in the morning, the current-season leaves showed similar or slightly higher E values than the one-year-old leaves. During the day, in both cultivars and at both leaf ages, E was higher in the afternoon. No effects on leaf gas exchanges due to the presence or absence of fruit on the shoot were found. Overall, there was satisfactory physiological adaptation for Arbequina to the conditions of Central Italy and for Maurino to the superintensive grove conditions.

Diurnal and Seasonal Changes in Photosynthetic Characteristics in Different Olive (Olea europaea L.) Cultivars

Diurnal and seasonal changes in photosynthetic characteristics, leaf area dry mass (ADM), and reducing sugar and total chlorophyll (Chl) contents of leaves of Frantoio, Leccino, and Maurino olive cultivars were investigated in Central Italy. Leaf net photosynthetic rate (PN) per unit leaf area changed during the growing season and during the day, but the cultivar did not significantly influence the changes. In both young and one-year-old leaves the highest PN values were observed in October, while the lowest values were recorded in August and December; during the day the highest PN values were generally found in the morning. The pattern of photosynthetic response to photosynthetic photon flux density (PPFD) of leaves was similar in the three genotypes. Sub-stomatal CO2 concentration (CI) tended to increase when PN decreased. The increase in CI was accompanied by a stomatal conductance to water vapor (gS) decrease. In general, PN and dark respiration rate (RD) were correlated. Transpiration rate (E), with no differences between the cultivars, increased from April to July, decreased greatly in August, then increased in October and finally decreased again in December. Leaf water content increased from April to June, remained high until mid July, decreased significantly in August, remaining constant until December with no differences associated with the cultivar. In both young and one-year-old leaves, the leaf water content per unit leaf area was slightly greater in Frantoio than in the other two cultivars. The one-year-old leaves had a higher Chl content than the young ones. The cultivar did not substantially influence the leaf reducing sugar content which decreased from April to August, when it reached the lowest level, then increased rapidly until October. During the day the reducing sugar content did not change significantly. The leaf ADM was slightly higher in Frantoio than in the other cultivars and one-year-old leaves had higher values than the young ones. Leaf ADM decreased from April to June and then tended to increase until December. During the day there were no substantial variations.

Effect of different leaf-to-fruit ratios on photosynthesis and fruit growth in olive (Olea europaea L.)

The influence of different leaf-to-fruit (l-t-f) ratios on leaf net photosynthetic rate (PN) and fruit characteristics in Olea europaea L. cv. Frantoio was evaluated in 2001 and 2002. In both years, at the end of June, at the end of July, and in mid-September (first, second, and third time of treatment, respectively), defoliation or fruit thinning were performed to give l-t-f ratios of 1/1, 3/1, 5/1, and 7/1 (about 5.1, 15.3, 25.6, and 35.8 cm2 of leaf area per fruit, respectively) on girdled and ungirdled peripheral shoots. PN showed substantial seasonal and diurnal variations. In ungirdled shoots, no differences due to the different l-t-f ratios were observed, whereas in girdled shoots PN tended to be lower in shoots with a high l-t-f ratio. In general, the values of leaf transpiration rate (E), stomatal conductance (gs), sub-stomatal CO2 concentration (Ci), and dark respiration rate (RD) were associated with those of PN. The starch and reducing sugar contents and area leaf dry mass (ADM) tended to be higher in leaves on girdled shoots with high l-t-f ratio, whereas in ungirdled shoots no differences related to the different l-t-f ratios were observed. The higher saccharide content in the leaves and the lower PN, in the presence of a high Ci, observed in girdled shoots with a high l-t-f ratio suggests that the depression in PN in these shoots may be the result of a feedback inhibition of the photosynthetic mechanism that regulates such a process. The l-t-f ratio did not have a substantial effect on fruit drop. In ungirdled shoots, the different l-t-f ratios did not produce significant differences in terms of fruit growth and leaf dry matter and saccharide contents, whereas in girdled shoots fruit growth increased as the l-t-f ratio increased, particularly when treatments were applied at the initial stage of fruit development. The percentage of oil in the pulp, on a dry matter basis, was not substantially influenced by girdling and l-t-f ratio. The abundant availability of assimilates seemed to cause earlier fruit ripening and, at the same time, retard fruit senescence (fruit detachment force). Shoot growth was slightly reduced by girdling. The abundant availability of assimilates, induced by girdling associated with high l-t-f ratio, stimulated flower induction.

Changes in Photosynthesis and Fruit Characteristics in Olive in Response to Assimilate Availability

The “source” level in the olive cultivar Leccino was varied by girdling at different stages of fruit growth. Afterwards, the effects on gas exchange, fruit growth, and ripening and blooming were studied. Girdling during fruit growth did not significantly influence net photosynthetic rate (PN) except in the last phase of fruit growth when the PN was reduced. In the girdled branch, PN began to decrease at the onset of starch accumulation because fruit growth ceased. In mid-November stomatal conductance (gs) and transpiration rate (E) were also reduced by girdling, whereas sub-stomatal CO2 concentration (Ci) increased in leaves from the girdled branches. The total chlorophyll content (Chl) tended to decrease in parallel with the reduced PN. Girdling did not substantially influence the leaf and shoot water contents. The large availability of assimilates seems to cause an earlier fruit ripening. In general, girdling increased fruit dry mass. Healing before the time when the majority of pulp growth occurs reduced the effect of girdling. June girdling increased the pit dry mass. Girdling at the beginning of August and September, compared to the control, increased the pulp dry mass, but the pit dry mass did not differ with respect to the control. The percentage of oil in the fruit, on a dry mass basis, increased with August and September girdlings, but the percentage of oil in the pulp did not change. Girdling reduced shoot growth, but the internode length was unchanged. Girdling slightly stimulated differentiation of flower buds.

Productive and vegetative behavior of olive cultivars in super high-density olive grove

In recent years, there has been an increase in interest in super high-density (SHD) olive (Olea europaea L.) groves because they offer early entry into production, increased productivity and the possibility of using modified mechanical vine harvesters. This study was carried out in a young SHD olive grove to examine vegetative, histo-anatomical and productive characteristics and oil quality of the Spanish Arbequina and Italian Maurino and Leccino cultivars, characterized by low, low-to-medium and high vigor, respectively. Arbequina had low vigor and limited development in height and width, as well as a high leaf/wood ratio. Maurino had a canopy volume similar to that of Arbequina and, despite a great tendency to grow in height, had low vigor, a rather compact vegetative habitus, but good lighting in the canopy and high production efficiency. In Maurino, a greater palisade parenchyma height and a larger exposed lateral surface area of the palisade parenchyma cells were observed. In the fourth year after planting, fruit production of Arbequina was about 30 % less than Leccino and Maurino. The oil content on a dry weight basis was slightly higher in Arbequina and Maurino than in Leccino. Oil quality was good for all cultivars.

CONTRIBUTION OF THE ADAXIAL AND ABAXIAL SURFACES OF OLIVE LEAVES TO PHOTOSYNTHESIS

Leaves of olive cultivars Frantoio and Maurino were irradiated with different irradiances from above, from below, or simultaneously from both directions to determine the contribution of the abaxial and adaxial leaf surfaces to photosynthesis. In both cultivars, irradiation of both sides of the leaf caused increases in net photosynthetic rate (PN) and apparent quantum yield compared to irradiating only one surface with the equal photosynthetic photon flux density (PPFD), but the PPFD needed to saturate PN decreased. At high and medium PPFD the PN determined at irradiating both leaf surfaces was less than the sum obtained at irradiation of only the upper or the lower surface with the same PPFD. At PPFD higher than 1000 µmol m-2 s-1 in cv. Frantoio and 1200 µmol m-2 s-1 in cv. Maurino, PN did not vary. At low PPFD (<200 µmol m-2 s-1), PN at irradiating the adaxial and abaxial leaf surfaces simultaneously was about the sum of the values obtained by irradiating the upper and lower surfaces separately. Consequently the compensation irradiance was reduced from about 50 µmol m-2 s-1 to about 30 µmol m-2 s-1 when irradiating both leaf surfaces. The natural leaf orientation of the olive cultivar influenced the utilization of radiant energy by the abaxial surface.