Both the biochemical and functional modifications of photosynthetic apparatus were observed during whole plant ontogeny. Net photosynthetic rate (Pn)» contents of photosystem (PS) 2 reaction centres, cytochromes 6559, and/ rates of electron- transport, cyclic and noncyclic photophosphorylation increased up till generative organs formation: a gradual decline followed as a result of senescence. The drop in activity of the electron-transport chain during senescence lead to the decline in content of PS2 reaction centres and Pn
A gradual reduction in leaf water potential (Ψleaf), net photosynthetic rate (PN), stomatal conductance, and transpiration rate was observed in two drought tolerant (C 306 and K 8027) and two susceptible (RW 893 and 899) genotypes subjected to water stress. The extent of reduction was lower in K 8027 and C 306 and higher in RW 893 and RW 899. Rewatering the plants after 5 d of stress restored PN and other gas exchange traits in all four cultivars. Water stress had no significant effect on variable to maximum fluorescence ratio (Fv/Fm) indicating that water stress had no effect on primary photochemistry of photosystem 2 (PS2). However, water stress reduced the efficiency of excitation energy transfer (F'v/F'm) and the quantum yield of electron transport (ΦPS2). The reduction was more pronounced in susceptible cultivars. Water stress had no significant effect on photochemical quenching, however, the non-photochemical quenching increased by water stress. and D. Subrahmanyam ... [et al.].
Since the discovery of Phaethon (the 'Geminid asteroid') in 1983 there has been renewed interest in the association of meteor showers with Earth-approaching asteroids. In the past the existence of several streams associated with different asteroids (in particular Adonis, Apollo, Hermes and Oljato) has been suggested but not proven. Here the 3759 meteor orbits determined at Adelaide in the 1960's have been compared to the orbits of all known
Aten-Apollo-Amor asteroids using a new and powerful search technique. Strong evidence is found for streams associated with Apollo-type asteroids Icarus, Hermes, Adonis, Oljato, Hephaistos, 5025 P-L, 1982 TA, and 1904 KB;, the final five in this list may be members of the Taurid-Arietid complex, as is Comet P/Encke.
No stream associated with 1862 Apollo was identified, but this may be due to the lack of observations at the appropriate solar longitude. No streams associated with any Aten or Amor asteroid
were found: this may be due to the limited detectability of their meteors, if they exist, because of their low geocentric velocities. In general streams were discovered for all asteroids coming within 0.1 AU of the Earth, having radiants observable from Adelaide and atmospheric velocities above about 22 km/sec : this suggests that meteoroid streams are a general feature of Earth-approaching
asteroids.