Photosynthetic pathways and the ecological distribution of the chenopodiaceae in Isreal

Summary Fifty-four species of the Chenopodiaceae in Israel were examined for their anatomical features, ¹³C values, habitat and phytogeographical distribution. 17 species have ¹³C values between -20 and -30and non-Kranz anatomy (NK) and are therefore considered as C₃ plants. 37 species have ¹³C values between -10 and -18 and Kranz or C₄-Suaeda type anatomy and are therefore considered as C₄ plants. Some C₄ plants have leaf structure which seems to be intermediate between the Kranz and the C₄-Suaeda type of leaf anatomy.The segregation of the species into photosynthetic groups shows tribal and phytogeographical grouping. Most of the C₃ Chenopods are either mesoruderal plants or coastal halophytes, with a distribution area which covers the Euro-Siberian as well as the Mediterranean phytogeographical regions. The C₄ Chenopods are mainly desert or steppe xerohalophytes with a distribution area which includes the Saharo-Arabian and/or Irano-Turanian phytogeographical regions.     

Suaeda monoica, a C(4) Plant without Typical Bundle Sheaths

Suaeda monoica Forssk. ex J. F. Gmel was found to possess the C₄ pathway of photosynthesis. The succulent leaves of Suaeda lack a green bundle sheath formation but have a layer of chlorenchyma, containing large and centripetally arranged chloroplasts, which surrounds the water tissue. We suggest that the proximity of a chlorenchymatous cell layer to the vascular bundles is not necessary for the operation of the C₄ pathway.     

Effects of salinity,N-nutrition and humidity on photosynthesis and protein metabolism ofChloris gayana Kunth

Summary Under high atmospheric humidity, Rhodes grass plants responded favourably to an increase in nitrate fertilization. Under low atmospheric humidity an optimum point was reached at lower N-treatment.Plants' growth was improved by a salinity treatment of up to 100 mM, at high atmospheric humidity. A higher salt concentration cancelled the favourable effect of added nitrate.The rise in yield which follows salt or nitrate treatments is apparently combined with an increase in activity of the key photosynthetic enzymes, Phosphoenol pyruvate carboxylase and Ribulose biphosphate carboxylase. A similar rise in activity is seen in nitrate reductase, a key enzyme in nitrogen metabolism. Evidently, all three enzymatic systems are not damaged in high salt treatments, and the potential photosynthetic capacity remained practically uneffected in all treatments. As no correlation could be found between transpiration and growth curves, it is assumed that the supply of CO₂ is also unhampered. Thus, the major negative effect of salinity, seems to be on protein synthesis, which eventually leads to disturbed growth.Agricultural Research Organization. The Volcanic Center.     

Effect of water regime on carbon isotope composition of lichens

δ¹³C values of the lichens Ramalina duriaei and Teloschistes villosus collected in their natural habitat were repeatedly measured during 2 years. Results show variations in the stable carbon isotope ratios (¹³C/¹²C). Such variations are correlated to the seasonal rainfall, i.e. low values of δ¹³C of the lichens during the winter and high values of δ¹³C during the dry summer. Relatively low δ¹³C values were obtained also in laboratory experiments with lichens grown under controlled humid conditions and in lichens collected from humid habitats.     

Effects of NaCl on the properties of phosphoenolpyruvate carboxylase from Suaeda monoica and Chloris gayana

The effects of NaCl on the kinetic properties of desalted phosphoenolpyruvate carboxylase (PEP carboxylase, EC 4.1.1.31) from two halophytes, Suaeda monoica Forssk. ex. J.F. Gmel and Chloris gayana Kunth. were investigated. The tolerance of PEP carboxylase to NaCl in the reaction medium depends on the enzyme pre-conditioning as well as on the concentration of its substrate PEP in the assay medium. Addition of PEP to the extraction and the storage medium, stabilizes the enzyme. Such a pre-treated enzyme is inhibited by NaCl in the presence of low concentrations of PEP in the assay medium but is activated by NaCl in the presence of PEP at concentrations above 1.0 m M . NaCl modifies the n_H value, K' and V_max, and seems to act as an allosteric effector.     

Annual variations of air-borne pollen in the Coastal Plain of Israel

A survey of airborne pollen was conducted during 1984 in the coastal plain of Israel. The flora of that area is continuously changing due to urbanization and agriculture, thus affecting the airborne pollen spectrum.

Significant pollen counts were monitored throughout the year, with a seasonal peak during spring. Meteorological parameters, such as wind velocity, wind direction and temperature affected pollen content of the air. Under certain conditions, even pollen of insect-pollinated plant species was found in the air.

The most conspicuous among the airborne pollen were olive, cypress and pine trees as well as pollen grains from the Poaceae, Amaranthaccae, Chenopodiaceae, Asteraceae, Brassicaceae and Urticaccae.

Results indicate that most of the airborne pollen grains were of local origin and from cultivated trees. Thus, it is possible to reduce airborne pollen contaminants around human habitations by selection of the proper non-allergenic ornamental plants.     

Biochemical Specialization of Photosynthetic Cell Layers and Carbon Flow Paths in Suaeda monoica

Suaeda monoica Frossk. ex J. F. Gmel is a C₄ plant with three different photosynthesizing cell layers. The outer chlorenchymatous layer shows a high activity of phosphoenolpyruvate (PEP) carboxylase but none of ribulose bisphosphate (RuBP) carboxylase. The electrophoretic protein band of RuBP carboxylase was missing in this layer. The second chlorenchymatous cells layer shows a very high activity of RuBP carboxylase and NAD malic enzyme and only traces of activity of PEP carboxylase. The third photosynthesizing cell type is comprised of the water tissue. It has moderate activities of RuBP carboxylase and PEP carboxylase. A model for carbon flow in Suaeda monoica leaves is proposed.     

Metabolism of sulfur compounds by whole filaments and heterocysts of Anabaena variabilis.

Filaments of the heterocyst-forming cyanobacterium Anabaena variabilis reproduced 35SO4(2)-, incorporating 35S into cysteine, methionine, glutathione, sulfolipid, and several unidentified metabolites. The majority of the incorporated label accumulated in reduced glutathione. Heterocysts isolated from labeled filaments contained the same major labeled products. Isolated, metabolically active heterocysts were unable to reduce 35SO4(2)-, but were able to incorporate 35S2- into cysteine and glutathione. The results suggest that the initial activation of SO4(2)- occurs in vegetative cells and that some reduced forms, possibly including S20, are translocated into heterocysts.     

Photosynthetic carbon fixation in the corollas of Petunia hybrida

Corollas of Petunia hybrida (cv. Hit Parade Rosa) flowers fixed ¹⁴CO₂ under both light and dark conditions. Rates of light fixation were much higher in mature pink corollas than in young, green corollas [57 and 9 nmol (ngchl)¹ min^-1], paralleling the development of chloroplasts in these tissues. Stomatal conductance in corollas was only 12% of that in green leaves, mainly due to the presence of few, and non-functioning stomata in the corolla. The activity and concentration of ribulose bisphosphate carboxylase (EC 4.1.1.39) in corolla extracts were only about 30% (per unit Chi) of those in extracts from green leaves. These results, together with previous results, might indicate a coordinated reduction in activity of systems participating in photosynthesis in corollas. The fixation products following a 6 s pulse with ¹⁴CO₂, were typical of C, plants in both corollas and green leaves, but a higher level of β-carboxylation products was found in the corollas. The activity of phosphoenol-pyruvate carboxylase (EC 4.1.1.31) (per unit protein) was similar in both tissues. Although the total carbon fixed by the corolla constituted only a small part of the metabolites required for flower development, certain photosynthetic metabolites might have a regulatory role in flower development.