A complete survey is presented of photosynthetic patfaway in the 27 species of the genus Cyperus occurring in Europe. Among them, tíiere are 20 species vsdth C4 photosynthesis and 7 species with C3 photosynthesis. In 14 species the pathway is repoited for the first time. Wifli different pattems, both C3 and C4 types occur from the Mediterranean region (35 °N) to the cool temperate region (52 “N). Atlantic current may háve a striking effect on the distňbution of wetland C4 sedges. Although the existence of rhizomes in C4 Cyperus perennials favours their survival at short summers of centra! and west Europe, low temperature at latě summer in the regions prevents them to complete seed development. Leaf anatomy indicates that diy summer in Mediterranean regions limits some of them due to dieir lavish water requirement. In the eastem and north Europe a long period of low temperature in winter may be the most important reason for the absence of C4 Cyperus species.
The 77 K fluorescence emission was measured on Chlorella cells at regular intervals during adaptatíon of high CO2 (1.8 % CO2 v/v) grown cells to air level of CO2. The ratíos of the peaks at 686 and 697 nm (photosystem 2, PS 2, fluorescence) to the peak at 720 nm (PS 1 fluorescence) decreased and approached a constant level in about 1.5 h. The extemal concentration of dissolved inorganic carbon (DlC) required for the half-maximum rates of C02-dependent O2 evolutíon, 5, also decreased and reached a constant level aíter the same period of adaptatíon. Hence the íncreased demand for ATP/NADPH during the CO2 assimilatíon by the ''C02-concentrating mechanism" induces the redistribution of excitation energy from PS 2 to PS 1 and increases formation of ATP by the cyclic photophosphorylatíon.
The diumal changes in leaf net photosynthetíc rate (P^) in two genotypes of wheat, T. aestivum (6x) cv. Sonalika and T. monococcum (2x) cv. G 1372, were analyzed in relatíon to stomatal (4) and mesophyll (/,J limitations of P^, ribulose-1,5- bisphosphate carboxylase (RuBPC) activity and saccharides content of the leaves. Pti decreased towards the aftemoon. The /„ was mostly contributing to the diumal decline in leaf at ear emergence stage. There was a decrease in activation statě of RuBPC in the aftemoon compared to forenoon. Associated with this a marked accumulation of saccharides in wheat leaf during the day was observed. Both the genotypes showed a more or less similar pattem of diumal changes in these parameters but differed in magnitude.
The effects of substrate-heating on gas exchange and leaf water potential of gerbera {Gerbera jamesonii H. Bolus ex Hook.) cv. Maria grown in rockwool as substráte were studied under a plastic greenhouse. Measurements of net photosynthetic rate (Pn), stomatal conductance to water vapour {g^, leaf to air vapour pressure difference (VPD), and leaf water potential ('P) were made along the day, at different dates, during two winter seasons. and were higher in plants grown with substrate-heating than in control plants. Control plants without substrate-heating showed higher VPD values. T' was generally more negative for the control plants. These differences may be ascribed to differences in root activity and/or root development, which are related to the temperature of the substráte.
Quercetin, rutin and phioridzin inhibited the activity of glyceraldehyde-3-phosphate dehydrogenase (GPD) complex from spinách leaves. At a concentiation of 5 X 10'5 M they decreased the rate of 3-phosphoglycerate (PGA) leduction by 90, 50- 80 and 30-40 % , respectively. The activity of the effectors depended on the tiine of isolation of enzymes and the corresponding level of endogenic phenolic compounds. To estimate the effect of the last factor, the enzj^e preparation was obtained in the presence and in the absence of insoluble polyvinylpyrrolidone (Polyciar AT). Using rutin it was shown that in the absence of endogenic phenols the inhibition of PGA reduction was decreased as compared with the variant without Polyciar AT. The effect of rutin was constant during the day. On the basis of data obtained the flavonoids are supposed to inhibit the Benson-Calvin cycie at its reducing stage; this effect may be cooperative and depend on quantitative and qualitative content of endogenic phenolic compounds.
Diurnal patterns of canopy net photosynthetic rates (jPií), evapotranspiration (£) and
water use efBciency (WŤJE = P^^E) of field grown irrigated wheat (Triticum
aestivum L. cv. WH 147) were studied fi'om tillering to maturity at Haryana
Agricultural University Farm, Hisar, India. Hie maximum photosynthetic rates
(^N, max) increased fi'om tillering to anthesis and declined at a rapid rate thereaňer till
maturity. Relatively high £'mav but low WUE„ax were recorded at tillering, milk ripe
and dough stages of growth. Diumally foUowed die course of photosynthetícaUy
active radiation (PAR) fiom tillering to wateiy ripeness but it declined at high PAR at
latter reproductive stages of growth. E was curvilinearly related to air temperature.
There was a lag of about 2 h between ^N, „lax (12.00 h) and E„,ax (14.00 h) during
the day. WUE was high fi-om 07.30 to 10.00 h, depressed during midday and a
slightly increased fi^om 15.00 to 16.00 h.Diurnal patterns of canopy net photosynthetic rates (jPií), evapotranspiration (£) and water use efBciency (WŤJE = P^^E) of field grown irrigated wheat (Triticum aestivum L. cv. WH 147) were studied fi'om tillering to maturity at Haryana Agricultural University Farm, Hisar, India. Hie maximum photosynthetic rates (^N, max) increased fi'om tillering to anthesis and declined at a rapid rate thereaňer till maturity. Relatively high £'mav but low WUE„ax were recorded at tillering, milk ripe and dough stages of growth. Diumally foUowed die course of photosynthetícaUy active radiation (PAR) fiom tillering to wateiy ripeness but it declined at high PAR at latter reproductive stages of growth. E was curvilinearly related to air temperature. There was a lag of about 2 h between ^N, „lax (12.00 h) and E„,ax (14.00 h) during the day. WUE was high fi-om 07.30 to 10.00 h, depressed during midday and a slightly increased fi^om 15.00 to 16.00 h.