Relationship of leaf anatomy with photosynthetic acclimation of Valeriana jatamansi was studied under full irradiance [FI, 1 600 μmol(PPFD) m-2 s-1] and net-shade [NS, 650 μmol(PPFD) m-2 s-1]. FI plants had thicker leaves with higher respiration rate (RD), nitrogen content per unit leaf area, chlorophyll a/b ratio, high leaf mass per leaf area unit (LMA), and surface area of mesophyll cell (Smes) and chloroplasts (Sc) facing intercellular space than NS plants. The difference between leaf thickness of FI and NS leaves was about 28 % but difference in photon-saturated rate of photosynthesis per unit leaf area (PNmax) was 50 %. This indicates that PNmax can increase to a larger extent than the leaf thickness with increasing irradiance in V. jatamansi. Anatomical studies showed that the mesophyll cells of FI plants had no open spaces along the mesophyll cell walls (higher Sc), but in NS plants wide open spaces along the mesophyll cell wall (lower Sc) were found. Positive correlation between Sc and PNmax explained the higher PNmax in FI plants. Increase in mesophyll thickness increased the availability of space along the mesophyll cell wall for chloroplasts (increased Sc) and hence PNmax was higher in FI plants. Thus this Himalayan species can acclimate to full sunlight by altering leaf anatomy and therefore may be cultivated in open fields. and S. Pandey, R. Kushwaha.
The ribulose 1,5-bisphosphate carboxylase (RuBPC) activity, protein content and net photosynthetic rate (P^) were estimated at monthly intervals from September 1990 to August 1991 in Chukrasia íabularis, Dolichandrom atrovirens, Eugenia jambolana, Gmelina arborea, Lamea coromandelica, Terminalia arjuna and Terminalia bellehca. The leaves of all these tree species showed significantly higher RuBPC activity during summer than in winter, when it was expressed on the basis of chlorophyll (Chl) content. RuBPC exhibited seasonal variations in its activity and these differed from one tree species to the other. When expressed on the basis of leaf area, the activity of RuBPC correlated with protein content, but not with P^.
Chlorophyll (Chl) fluorescence from greening and fiilly green barley leaves was analyzed using a phase-modulated fluorimeter. Inunediately following the irradiation of fiilly-etiolated leaves, a pool of (newly-synthesised) Chl/chlorophyllide was detected with a fluorescence lífetime similar to that of these pigments in solution. After some hours, the major fluorescence component was a short-lifetime species which we believe to represent photosystem 2. Selective inhibition of polypeptide synthesis in either the chloroplast or cytosol greatly reduced the extent of Chl assimilation and gave rise to novel fluorescence-lifetime profiles which are believed to arise flom complexes in various stages of assembly. Hence angiosperms háve evolved control systems to lim't the appearance of free Chl; this involves close co- ordination between pigment and polypeptide synthesis.