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.
The fundamental cause of down-regulation of photosynthesis at elevated carbon dioxide concentration (EC) is thought to be a slower rate of utilization of saccharides than their stimulated rate of production, but there are few studies directly supporting this idea under field conditions. We hypothesized that within Brassica oleracea, down-regulation would not occur in kohlrabi because it has a large sink for saccharides in an enlarged stem, but would occur in collards, which lack this sink. Field tests were consistent with this hypothesis. In collards, the degree of down-regulation of photosynthesis in plants grown at EC varied depending on the daily integral of photosynthetically active radiation (PAR) of the day prior to the measurement of photosynthetic capacity, as did leaf saccharide content. However, EC did not result in lower leaf contents of chlorophyll, soluble protein, ribulose-1,5-bisphosphate carboxylase, or nitrate in collards, nor was there any evidence of a triose phosphate utilization rate limiting photosynthesis. Experiments in controlled environment chambers confirmed that there was a threshold response for the down-regulation of photosynthesis in collards at EC to the PAR of the previous day, with down-regulation only occurring above a minimum daily integral of PAR. Down-regulation of photosynthesis could be induced in plants grown at ambient carbon dioxide by a single night at low temperature or by a single day with high PAR and EC. In the controlled environment study, the degree of down-regulation of photosynthesis was highly correlated with leaf glucose, fructose, and sucrose contents, and less well correlated with starch content. Hence down-regulation of photosynthesis at EC in collards in the field represented feedback inhibition from the accumulation of soluble saccharides and day-to-day variation in its occurrence was predictable from the weather. and J. A. Bunce, R. C. Sicher.
Gas exchange and chlorophyll (Chl) fluorescence were measured on young mature leaves of rose plants (Rosa hybrida cvs. First Red and Twingo) grown in two near-to-tight greenhouses, one under control ambient CO2 concentration, AC (355 µmol mol-1) and one under CO2 enrichment, EC (700 µmol mol-1), during four flushes from late June to early November. Supply of water and mineral elements was non-limiting while temperature was allowed to rise freely during daytime. Leaf diffusive conductance was not significantly reduced at EC but net photosynthetic rate increased by more than 100 %. Although the concentration of total non-structural saccharides was substantially higher in the leaves from the greenhouse with EC, ΦPS2 (quantum efficiency of radiation use) around noon was not significantly reduced at EC indicating that there was no down-regulation of electron transport. Moreover, CO2 enrichment did not cause any increase in the risk of photo-damage, as estimated by the 1 - qP parameter. Non-photochemical quenching was even higher in the greenhouse with EC during the two summer flushes, when temperature and photosynthetic photon flux density (PPFD) were the highest. Hence rose photosynthesis benefits strongly from high concentrations of atmospheric CO2 at both high and moderate temperatures and PPFD. and L. Urban ... [et al.].
The effect on traits of photosynthesis and water relations of assimilate demand was studied in olive tree that has strong alternate bearing. The diurnal and seasonal leaf gas exchanges, area dry mass, and saccharide and chlorophyll (Chl) contents were measured by comparing shoots with fruit of "on-trees" (heavy fruit load) with shoots without fruit on both "on-trees" and "off-trees" (light fruit load). In spite of large seasonal and diurnal differences, leaf net photosynthetic rate (PN), stomatal conductance (gs), sub-stomatal CO2 concentration (C1), transpiration rate (E), and respiration rate (RD) were not significantly influenced by fruit load or by the presence or absence of fruit on the shoot. An only exception was at the beginning of July when the one-year-old leaves on shoots with fruit had slightly higher PN and E than leaves on shoots without fruit. Water content, Chl and saccharide contents, and area dry mass of the leaf were not substantially influenced by the presence/absence of fruit on the shoot or fruit load. Hence the sink demand, associated with fruit growth, did not improve leaf photosynthetic efficiency in olive.
Mulberry genotypes were subjected to salinity (0-12 mS cm-1) in pot culture experiment. Chlorophyll and total carotenoid contents were reduced considerably by salinity. At low salinity, photosynthetic CO2 uptake increased over the control, but it decreased at higher salinity. Contents of soluble proteins, free amino acids, soluble sugars, sucrose, starch, and phenols increased at salinity of 1-2 mS cm-1 and decreased at higher salinity (8-12 mS cm-1). Glycine betaine accumulated more than proline, the maximum accumulation of both was at salinity of 2-4 mS cm-1. Among the genotypes studied, BC2-59 followed by S-30 showed better salinity tolerance than M-5. and P. Agastian, S. J. Kingsley, M. Vivekanandan.
Seedlings of Erythrina variegata Lam. exposed to flooding for 10 d showed significant reduction in height, growth rates (leaf area in plant, leaf area index, relative growth rate, and specific leaf mass), biomass, chlorophyli (Chl) and carotenoid contents, and thylakoid membrane organization. Application of triacontanol partially compensated these effects and promoted height, biomass and Chl content. Starch and sugar contents were significantly higher in leaves of flooded seedlings.
The effects of short-term exposure to chilling temperature (10 °C) on sucrose synthesis in leaves of the cold-tolerant sugarcane cultivars Saccharum sinense R. cv. Yomitanzan and Saccharum sp. cv. NiF4, and the cold-sensitive cultivar S. officinarum L. cv. Badila were studied. Plants were grown at day/night temperatures of 30/25 °C, and then shifted to a constant day/night temperature of 10 °C. After 52-h exposure to the chilling temperature, sucrose content in the leaves of NiF4 and Yomitanzan showed a 2.5- to 3.5-fold increase relative to that of the control plants that had been left on day/night temperatures of 30/25 °C. No such increase was observed in Badila leaves. Similarly, starch content in the leaves of NiF4 and Yomitanzan was maintained high, but starch was depleted in Badila leaves after the 52-h exposure. During the chilling temperature, sucrose phosphate synthase (SPS; E.C.2.4.1.14) activity was relatively stable in the leaves of NiF4 and Yomitanzan, whereas in Badila leaves SPS activity significantly decreased. There was no significant change in cytosolic fructose-1,6-bisphosphatase activity for the three cultivars at the chilling temperature. This supports the hypothesis that: (1) on exposure to chilling temperature, sucrose content in sugarcane leaves is determined by the photosynthetic rate in the leaves, and is not related to SPS activity; (2) SPS activity in sugarcane leaves at chilling temperature is to be determined by sugar concentration in the leaves. and Yu-Chun Du, Akihiro Nose.
In leaves of four tomato (Lycopersicon esculentum Mill.) cultivars (Red Cloud, Floradade, Peto 95, and Scorpio) the contents of chlorophyll (Chl) (a+b), Chl a, and β-carotene decreased due to 100 mM NaCl treatment as compared with those of controls. The contents of soluble sugars and total saccharides were significantly increased in leaves of NaCl-treated plants, but the starch content was not significantly affected. Transmission electron microscopy indicated that in leaves of NaCl-treated plants, the chloroplasts were aggregated, the cell membranes were distorted and wrinkled, and there was no sign of grana and thylakoid structures in chloroplasts. and R. A. Khavari-Nejad, Y. Mostofi.
Application of the electrostatic precipitator (ESP) dust to soil and leaves of Cajanus cajan, Vigna mungo, Vigna radiata, Vigna catjung and Glycina max increased biomass, chloroplast pigments, Chemical constituents and enzyme activities of leaves, besides crop productivity evidently indicating that the dust acted as a fertilizer. The net photosynthetic rate, photosystem 2 activity and rate of transpiration were not altered in špite of the dust forming a thin uniform coating ověř the leaf surface. The contents of intermediary N-compounds like allantoin, allantoic acid and total ureides of the leaves, which might serve as an indirect evidence of symbiotic N2-fixation, were higher in the treated plants. There were increments in free proline, soluble proteins, total nitrogen, nitrates, nitrites, soluble sugars and phenols in the treated plants. The concentrations of ffee amino acids, soluble starch, total sucrose and water soluble SH compounds of the leaves of the control and treated plants did not show any significant difference. The activity of superoxide dismutase was significantly higher which possibly indicated its role in alleviation of H2O2 and Oj toxicity. Enzymes like nitráte reductase, nitrite reductase, glutamine S3mthetase, acid and alkaline phosphatases, carbonic anhydrase, catalase, glutathione reductase and ascorbate peroxidase also functioned normally. In the treated plants, the concentration of ascorbic acid was significantly higher in the roots and nodules indicating the possible role of ascorbic acid in stress alleviation.
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. and P. Proietti, F. Famiani, A. Tombesi.