The number of C4 plants living in Europe is increased to 120, and data on geographic origin, metabolic subtype, microecology and biotype, are given and compared with previous data. Our data agree with current ideas regarding the origin and biotype of the C4 plants, and only partially regarding ecology. At present, many C4 plants grow on disturbed sites or in stressed conditions, but ťhere is a lesser number of xerophytes than is currently thought and, conversely, some of them grow in favourable conditions. Among the latter mentioned, hydrophytic plants stand out because of their relatively great number and originality, as well as because no previous work on the ecology of C4 plants has indicated this.
We measured the diurnal changes in net photosynthetic rate (PN) and stomatal conductance (gs) of the leaves of a liana, Enkleia malaccensis Griff. (Thymelaeaceae), at the canopy level in the lowland tropical rainforest at Pasoh, Peninsular Malaysia. The measurements were made from a canopy walkway system, 30 m from the ground for 3 d in March 2003. PN increased with increasing photosynthetically active radiation (PAR) before noon, though PN was not enhanced by the strong radiation hit in the afternoon. Plotting g s at saturating PAR (>0.5 mmol m-2 s-1) against the vapour pressure deficit (VPD) failed to reveal a significant correlation between VPD and gs, and gs became very low at VPD >2.5 kPa. The relationship between PN and gs was fitted on the same regression line irrespective of measuring day, indicating that this relationship was not influenced by either VPD or leaf temperature (T L). Therefore, in the liana E. malaccensis, an increase in VPD leads to partial stomatal closure and, subsequently, reductions in PN and the midday depression of PN of this plant. and A. C. Tay ... [et al.].
Super-rice hybrids are two-line hybrid rice cultivars with 15 to 20 % higher yields than the raditional three-line hybrid rice cultivars. Response of photosynthetic functions to midday photoinhibition was compared between seedlings of the traditional hybrid rice (Oryza sativa L.) Shanyou63 and two super-rice hybrids, Hua-an3 and Liangyoupeijiu. Under strong midday sunlight, in comparison with Shanyou63, the two super-rice hybrids were less photoinhibited, as indicated by the lower loss of the net photosynthetic rate (PN), the quantum yield of photosystem 2 (ΦPS2), and the maximum and effective quantum yield of PS2 photochemistry (Fv/Fm and Fv'/Fm'). They also had a much higher transpiration rate. Hence the super-rice hybrids could protect themselves against midday photoinhibition at the cost of water. The photoprotective de-epoxidized xanthophyll cycle components, antheraxanthin (A) and zeaxanthin (Z), were accumulated more in Hua-an3 and Liangyoupeijiu than in Shanyou63, but the size of xanthophyll cycle pool of the seedlings was not affected by midday photoinhibition. Compared to Shanyou63, the super-rice hybrids were better photoprotected under natural high irradiance stress and the accumulation of Z and A, not the size of the xanthophyll pool protected the rice hybrids against photoinhibition. and Q. A. Wang, C. M. Lu, Q. D. Zhang.
In leaves of Sdndapsus aurea L. after a mild heat treatment (5 min 46-49 “C), the chlorophyll fluorescence yield, measured with a pulse amplitudě modulation (PAM) fluorometer and excited with short pulses of actínic radiation (50-500 ms), increased during excitation up to the maximum F,„. The fluorescence yield then decreased to the minimum (where Fn^„ may be lower than the initial fluorescence yield Fq) and rose again to the second maximum F„^, which occurred some seconds (2-20) after that pulse of the actínic radiation.
Having explained existing differences in imderstanding the term of "stress", a brief OverView of historical development of studies on relationships between the minerál nutrition and photosynthesis is given. Effects of minerál nutrients on photosynthesis are illustrated mainly with results obtained firom nitrogen-deficient plants. Changes in photosynthesis brought about by phosphorus deficiency háve also been described in detail. Recent papers on the effects of other minerál nutrients háve been included too. It has been emphasized that (7) minerál nutrients affect the photosynthesis at all levels of plant structure, (2) the photosynthesis has considerable influence on minerál nutrients uptake, distribution and utilization, (3) the photosynthesis should always be considered as only one factor among many others that are modifíed by changes of the minerál nutrition.
Photoinactivation of photosystem 2 (PS2) results from absorption of so-called "excessive" photon energy. Chlorophyll a fluorescence can be applied to quantitatively estimate the portion of excessive photons by means of the parameter E = (F - F0')/Fm', which reflects the share of the absorbed photon energy that reaches the reaction centers (RCs) of PS2 complexes with QA in the reduced state ('closed' RCs). Data obtained for cotton (Gossypium hirsutum), bean (Phaseolus vulgaris), and arabidopsis (Arabidopsis thaliana) suggest a linear relationship between the total amount of the photon energy absorbed in excess (excessive irradiation) and the decline in PS2 activity, though the slope may differ depending on the species. This relationship was sensitive not only to the leaf temperature but also to treatment with methyl viologen. Such observations imply that the intensity of the oxidative stress as well as the plant's ability to detoxify active oxygen species may interact to determine the damaging potential of the excessive photons absorbed by PS2 antennae. Energy partitioning in PS2 complexes was adjusted during adaptation to irradiation and in response to a decrease in leaf temperature to minimize the excitation energy that is trapped by 'closed' PS2 RCs. The same amount of the excessive photons absorbed by PS2 antennae led to a greater decrease in PS2 activity at warmer temperatures, however, the delay in the development of non-photochemical and photochemical energy quenching under lower temperature resulted in faster accumulation of excessive photons during induction. Irradiance response curves of EF suggest that, at high irradiance (above 700 μmol m-2 s-1), steady-state levels of this parameter tend to be similar regardless of the leaf temperature. and D. Kornyeyev, A. S. Holaday, B. A. Logan.
The authors treat a manuscript missal unknown to this day by experts, which is housed at the Scientific Library in Olomouc (M III 106). After having analysed the manuscript in the line of codicology (Š. Kohout), history of arts (J. Hrbačova), and musicology (S. Červenka), they conclude that this codex was intended for the needs of the Benedictine Convent in Opatovice nad Labem. It was created shortly after the year 1354, its illuminations are the work of a Prague workshop associated with the court of King Charles IV, which participated in the production of a series of exclusive manuscripts, e. g. Liber viaticus of the Bishop Johannes Noviforensis. The Viaticus and the missal of Opatovice are on the same line in terms of decoration. The missal was probably ordered by the then Benedictine Abbot Neplach who maintained frequent official contacts with the Bishop occupying the office of chancellor to Charles IV.