Showing papers on "Plant physiology published in 1983"
TL;DR: A brief survey of the different possibilities to measure Chl fluorescence changes is given and emphasis will be put on such techniques which can be applied in plant physiological work.
Abstract: A part of the light absorbed by green plants, is re-emitted in form of chlorophyll (Chl) fluorescence. This constitutes a large optical signal which can be easily detected, provided the wavelength of excitation is chosen so as not to overlap the wavelength of emission (670-770 nm). As early as 1874 N.J.C. MUller [1 ] observed Chi fluorescence changes in green leaves with his bare eyes, using a suitable combination of colored glasses. While already Mtiller [1] recognised a correlation between Chl fluorescence and assimilation, a systematic study of this correlation became possible only more than half a century later with the development of light sensitive devices and signal recorders, as first applied by H. Kautsky and his co-workers [2-5] Hence, progress in the study of Chl fluorescence has always been closely linked with advancements in measuring techniques. At present, such advancements are apparent e.g. in the fields of fiber optics, semiconductor photodevices, transient recorders and microcomputers. This article intends to give a brief survey of the different possibilities to measure Chl fluorescence changes. Emphasis will be put on such techniques which can be applied in plant physiological work. Forthcoming articles of this series will deal with the questions of how to interpret Chl fluorescence changes and how to apply this tool in the characterisation of the physiological state of the plant.
140 citations
TL;DR: The dynamics of leaf chlorophyll level, nitrogen content, photosynthesis and stomatal conductance were followed in detail in two cultivars of maize during a short period of water stress, applied at tasseling, and during the subsequent recovery phase, and it was concluded that the stress-induced loss ofchlorophyll is not mediated by a lack of nitrogen.
Abstract: The dynamics of leaf chlorophyll level, nitrogen content, photosynthesis and stomatal conductance were followed in detail in two cultivars of maize (Zea mays) during a short period of water stress, applied at tasseling, and during the subsequent recovery phase. Plants used in the experiment were grown in sand-nutrient solution culture under field weather conditions. Water stress reduced chlorophyll levels, stomatal conductance and photosynthesis, but the nitrogen content of the leaves was not affected. It is concluded that the stress-induced loss of chlorophyll is not mediated by a lack of nitrogen. Considerable differences were observed between genotypes in the rate of post-stress recovery of chlorophyll level. Recovery, upon rewatering, of stomatal conductance and photosynthesis preceded that of chlorophyll level. Losses of up to 40% of leaf chlorophyll content were insufficient to affect rates of photosynthesis measured at mid-day.
75 citations
Journal Article•
25 citations
TL;DR: Calculation of diffusive resistance to H2O(r) and SO2(r′) showed that the ratio of r′/r was 1.9 irrespective of species and coincided well with the theoretical value based on molecular diffusion, making clear that the absorption of SO2 was dependent upon the gas exchange capacity of leaf blade.
Abstract: Photosynthetic rate, transpiration rate and SO2 absorption rate were simultaneously measured under exposure to SO2 (0.1–1.0 μl l
−1) for 5 or 8 hr in six species belonging to C4 or C3 plants (Zea mays, Sorghum vulgare, Amaranthus tricolor, Oryza sativa, Avena sativa andHelianthus annuus). Distinct interspecific differences were found as to the extent of inhibition of photosynthetic rate. Calculation of diffusive resistance to H2O(r) and SO2(r′) showed that the ratio of r′/r was 1.9 irrespective of species and coincided well with the theoretical value based on molecular diffusion. Thus it was made clear that the absorption of SO2 was dependent upon the gas exchange capacity of leaf blade. Using the ratio of r′/r the rate of SO2 absorption could be calculated from transpiration rate and was compared with the inhibition rate of photosynthesis. In three C4 species, the inhibition of photosynthesis increased linearly with the amount of SO2 absorbed during a 5-hour period. The pattern of inhibition of photosynthesis inA. sativa andH. annuus among C3 species was similar to that of C4 species until the amount of SO2 absorbed reached 60 mg-SO2 m−2 above which the inhibition abruptly increased. The inhibition of photosynthesis inO. sativa was exceptionally severe even with only a small amount of SO2 absorbed.
11 citations
TL;DR: Both photosynthetic rates per unit leaf area and shoot-root ratios were affected, however, the carbon/nitrogen economies of the plants and the fraction of the total plant weight allocated to nodule growth were unaffected.
Abstract: The possibilities of using light quality treatments to gain an understanding of the mechanisms controlling the allocation of photosynthate for symbiotic nitrogen fixation were studied. White clover (Trifolium repens) plants were grown at the same photon irradiance in red, blue and green light treatments. Growth, nodulation and the carbon/nitrogen economies of the plants were measured. Both photosynthetic rates per unit leaf area and shoot-root ratios were affected by the treatments. However, the carbon/nitrogen economies of the plants and the fraction of the total plant weight allocated to nodule growth were unaffected.
11 citations
TL;DR: The results presented here support the view that phytochrome exerts its effect on lettuce seed germination by means of GA rather than via an independent pathway.
Abstract: Experiments were carried out to explore the involvement of the plant hormone gibberellin (GA) in the light-induced germination of lettuce seeds. Three growth retardants known to be inhibitors of GA biosynthesis were tested for their effect on red-light-induced germination. Chlormequat chloride (CCC) and AMO-1618 had no effect, but ancymidol was strongly inhibitory. Moreover, the inhibition caused by ancymidol was completely overcome by GA3. CCC and AMO-1618 inhibit the formation ofent-kaurene, while ancymidol blocks the oxidation ofent-kaurene toent-kaurenoic acid. Ancymidol also was found to inhibit GA-induced dark germination of lettuce seeds, and this inhibition was partially reversed by higher levels of GA. Therefore, the results suggest two possibilities for the relationship between phytochrome and GA in this system: first, the rate-limiting step in the germination of light-sensitive lettuce seeds, that which is regulated by phytochrome, is the oxidation ofent-kaurene toent-kaurenoic acid. Alternatively, red-light treatment may result in the release of active GAlike substances which, in turn, induce germination. In either case the results presented here support the view that phytochrome exerts its effect on lettuce seed germination by means of GA rather than via an independent pathway.
10 citations
TL;DR: It is concluded that low concentrations of methionine sulfoximine (up to 10 mM) have no direct effect on the photosynthetic process.
Abstract: Methionine sulfoximine provided at a concentration which inhibits photosynthesis in intact leaves (10 mM) had no significant influence on the rate of photosynthesis of isolated pea leaf chloroplasts In contrast, ammonium, 3-(3,4-dichlorophenyl)-1,1-dimethylurea, and D,L-glyceraldehyde all strongly inhibited the photosynthesis of isolated chloroplasts We conclude that low concentrations of methionine sulfoximine (up to 10 mM) have no direct effect on the photosynthetic process