Plant physiology

About: Plant physiology is a research topic. Over the lifetime, 1537 publications have been published within this topic receiving 72038 citations.

Effect of ammonium and nitrate on net photosynthesis, flower formation, growth and yield of eggplants (Solanum melongena L.)

Abstract: Eggplants (Solanum melongena L. cv. Bonica) were grown in a glasshouse during summer under natural light with one unbranched shoot or one shoot with 3 to 4 branches and with or without fruit in quartz sand buffered and not buffered with 0.5% CaCO3 (w : v), respectively. Nutrient solutions supplied contained nitrate or ammonium as the sole nitrogen source. Compared with nutrient solutions containing nitrate (10 mM), solutions containing ammonium (10 mM) caused a decrease in net photosynthesis of eggplants during early stages of vegetative growth when grown in quartz sand not buffered with CaCO3. The decrease was not observed before leaves showed interveinal chlorosis. In contrast, net photosynthesis after bloom at first increased more rapidly in eggplants supplied with ammonium than with nitrate nitrogen. However, even in this case, net photosynthesis decreased four weeks later when ammonium nutrition was continued. The decrease was accompanied by epinasty and interveinal chlorosis on the lower leaves and later by severe wilting, leaf drop, stem lesions, and hampered growth of stems, roots, and fruits. These symptoms appeared later on plants not bearing fruits than on plants bearing fruits. If nutrient solutions containing increasing concentrations of ammonium (0.5–30 mM) were supplied after the time of first fruit ripening, shoot growth and set of later flowers and fruits were promoted. In contrast, vegetative growth and reproduction was only slightly affected by increasing the concentration of nitrate in the nutrient solutions. In quartz sand buffered with CaCO3 ammonium nutrition caused deleterious effects only under low light conditions (shade) and on young plants during rapid fruit growth. If eggplants were supplied with ammonium nitrogen before bloom, vegetative growth was promoted, and set of flowers and fruit occurred earlier than on plants supplied with nitrate. Furthermore, the number of flowers and fruit yield increased. These effects of ammonium nutrition were more pronounced when plants were grown with branched shoots than with unbranched shoots. The results indicate that vegetative and reproductive growth of eggplants may be manipulated without causing injury to the plants by supplying ammonium nitrogen as long as the age of the plants, carbohydrate reserves of the roots, quantity of ammonium nitrogen supplied, and pH of the growth medium are favourable. T W Rufty Section editor

Improvement of photosynthesis in rice (Oryza sativa L.) as a result of an increase in stomatal aperture and density by exogenous hydrogen sulfide treatment

Abstract: Hydrogen sulfide (H2S) is considered to be the third gaseous signaling molecule after NO and CO, and it plays an active role in regulating the physiological processes of plants and animals. In this work, rice cultivar ‘IIyou 084’ seedlings were treated with NaHS, which is a donor of H2S, for 10 days, and its effects on growth and physiology, including photosynthesis, photorespiration, chlorophyll fluorescence, and stomata, were investigated. The data revealed that 0.01 mM of H2S improved rice biomass and chlorophyll content, while higher concentrations of H2S had an adverse effect on these parameters. Photosynthetic rate, stomatal conductance, and ribulose-1,5-bisphosphate carboxylase (EC 4.1.1.39) activity also increased under 0.01 mM H2S treatment. However, photosynthetic oxygen evolution rate, photosynthetic electron transfer, and photochemical efficiency of PSII were not affected by H2S treatment. In addition, photosynthesis oxygen sensitivity, CO2 compensation point, and glycolate oxidase (EC 1.1.3.1) activity reduced by H2S treatment, and thus photorespiration was down-regulated. Under light, stomatal aperture and density increased by treatment with 0.01 mM H2S. On the basis of these results, it can be deduced that 0.01 mM of H2S treatment improved photosynthesis in rice by increasing its stomatal aperture and density, which may result from reduced photorespiration.

Heavy metal-hormone interactions in rice plants: Effects on growth, net photosynthesis, and carbohydrate distribution

Abstract: The effect of external applications of gibberellins (GA3) and abscisic acid (ABA) on the growth, carbohydrate content, and net photosynthesis of heavy metal-stressed rice plants (Oryza sativa cv. Bahia) was investigated. Treatment with cadmium (0.1 mm) and nickel (0.5 mm) inhibited rice growth and stimulated carbohydrate accumulation, especially in seeds from which seedlings were developing, stems, and first leaves. The addition of GA3 (14 μm) to the rice culture solution together with Cd or Ni partially reversed the effects of heavy metals, stimulating growth as well as mobilization of carbohydrate reserves in seeds from which seedlings had developed. GA3 increased the sugar content in roots and second and third leaves and also modified the carbohydrate distribution pattern compared with heavy metal-treated plants. In contrast to GA3, ABA (19 μm) supplied to rice cultures potentiated the effect of heavy metals, inhibiting the growth of young leaves and the translocation of storage products from source to sink organs. In addition, sugars were accumulated in roots and second leaf but not in the third leaf, the extension in length of which was also inhibited by the treatment. Net photosynthesis rates recovered transitorily in Cd-treated plants after the addition of hormones. The possible relationship between growth and carbohydrate distribution, as well as the involvement of hormones, in the response of plant to heavy metal stress is discussed.

Effects of salt stress on photosynthesis, PSII photochemistry and thermal energy dissipation in leaves of two corn (Zea mays L.) varieties.

Abstract: The effect of four different NaCl concentrations (from 0 to 102 mM NaCl) on seedlings leaves of two corn (Zea mays L.) varieties (Aristo and Arper) was investigated through chlorophyll (Chl) a fluorescence parameters, photosynthesis, stomatal conductance, photosynthetic pigments concentration, tissue hydration and ionic accumulation. Salinity treatments showed a decrease in maximal efficiency of PSII photochemistry (Fv/Fm) in dark-adapted leaves. Moreover, the actual PSII efficiency (ϕPSII), photochemical quenching coefficient (qp), proportion of PSII centers effectively reoxidized, and the fraction of light used in PSII photochemistry (%P) were also dropped with increasing salinity in light-adapted leaves. Reductions in these parameters were greater in Aristo than in Arper. The tissue hydration decreased in salt-treated leaves as did the photosynthesis, stomatal conductance (gs) and photosynthetic pigments concentration essentially at 68 and 102 mM NaCl. In both varieties the reduction of photosynthesis was mainly due to stomatal closure and partially to PSII photoinhibition. The differences between the two varieties indicate that Aristo was more susceptible to salt-stress damage than Arper which revealed a moderate regulation of the leaf ionic accumulation.