Deke Xing

Photosynthetic characteristics involved in adaptability to Karst soil and alien invasion of paper mulberry (Broussonetia papyrifera (L.) Vent.) in comparison with mulberry (Morus alba L.)

Unlike mulberry (Morus alba, M.a.), paper mulberry (Broussonetia papyrifera, B.p.) can acclimate to Karst soil and incline to alien invasion. The photosynthetic parameters, diurnal changes of carbonic anhydrase, and chlorophyll fluorescence induction, and water potential were measured on sunny days (SD) and cloudy days (CD). Photosynthetic midday depression occurred in B.p. but not in M.a. The irradiance-and CO2-saturated photosynthetic rates of B.p. were significantly higher than those of M.a. There was no significant difference in water use efficiency between the two species on a SD. The maximum fluorescence, maximum quantum yield, photochemical quenching, and relative electron transport rate in the leaves of B.p. were much higher than those in M.a. The activity of carbonic anhydrase (CA) of B.p., on either an SD or a CD, was much greater than that of M.a. Higher transpiration rate (E) and net photosynthetic rate (PN) of B.p. resulted in the lack of water in mesophyll cells. Although a higher CA activity of B.p. supplied both water and CO2 for the photosynthesis of mesophyll cells, water in mesophyll cells was the factor limiting photosynthesis, and the intercellular CO2 concentration of B.p. was high and stable.

Effect of bicarbonate treatment on photosynthetic assimilation of inorganic carbon in two plant species of Moraceae

Excessive levels of bicarbonate adversely affect the growth and metabolism of plants. Broussonetia papyrifera (L.) Vent. and Morus alba L., belonging to family Moraceae, possess the favorable characteristics of rapid growth and adaptability to adverse environments. We examined the response of these two plant species to bicarbonate stress in terms of photosynthetic assimilation of inorganic carbon. They were exposed to 10 mM sodium bicarbonate in the culture solution for 20 days. The photosynthetic response was determined by measuring the net photosynthetic rate of the leaf, water-use efficiency, and chlorophyll fluorescence on days 10 and 20. The bicarbonate-use capacity of the plants was studied by measuring the carbonic anhydrase activity and the compositions of the stable carbon and hydrogen isotopes. The photosynthetic response to high concentration of bicarbonate varied with plant species and treatment durations. High concentrations of bicarbonate decreased the photosynthetic assimilation of inorganic carbon in the two plant species to half that in the control plants on day 10. Bicarbonate treatment did not cause any damage to the reaction centers of photosystem II in Morus alba; it, however, caused a decline in the quantum efficiency of photosystem II in B. papyrifera on day 20. Moreover, B. papyrifera had a greater bicarbonate-use capacity than M. alba because carbonic anhydrase converted bicarbonate to CO2 and H2O to a greater extent in B. papyrifera. This study showed that the effect of bicarbonate on photosynthetic carbon metabolism in plants was dual. Therefore, the concentration of bicarbonate in the soil should first be considered during afforestation and ecological restoration in karst areas.

Effect of Phosphorus Deficiency on Photosynthetic Inorganic Carbon Assimilation of Three Climber Plant Species

BackgroundP deficiency in karst areas significantly influenced leaf photosynthesis and carbon metabolisms in plants which were bad for plant growth. Meanwhile, fertilizer application would cause lots of environmental problems. Therefore planning and developing P deficiency-resistant plants in karst areas are important to prevent shortage of P resources and reduce the environmental impacts of P supplementation.ResultsThis study examined the photosynthetic response of three climber plant species, namely, Pharbitis nil (Linn.) Choisy, Lonicera pampaninii Levl, and Parthenocissus tricuspidata (Sieb.et Zucc.) Planch to phosphorus (P) deficiency stress. The plants were exposed to P deficiency stress at three treatments of 0.125 mM, 0.031 mM, and 0 mM for 30 d; 0.250 mM P was used as the control. Photosynthetic responses were determined by measurement of leaf photosynthesis, chlorophyll fluorescence, carbonic anhydrase activity, and stable carbon isotope ratios. Pharbitis nil showed high CA activity, more negative δ13C values and could maintain long-term stable photosynthetic capacity. Lonicera pampaninii also showed high CA activity but positive δ13C values compared to Pharbitis nil, and its photosynthetic capacity decreased as P deficiency stress increased. Parthenocissus tricuspidata had a low photosynthesis and positive δ13C values compared to Pharbitis nil, it could grow normally even under 0 mM P.ConclusionsPharbitis nil was tolerant to long-term, severe P deficiency stress, a finding that is attributed to its stable PSII and regulation of carbonic anhydrase. Lonicera pampaninii showed a poor adaptability to short-term P deficiency, but exhibited long-term tolerance under 0.125 mM P concentration. Parthenocissus tricuspidata was tolerant to long-term P deficiency stress, may exhibit a stomatal limitation. Besides, P deficiency stress had little effect on the way of inorganic carbon utilization of the three climber plants. Different adaptation mechanisms to P deficiency stress should be considered for the selection of species when developing P deficiency-resistant plants.

Photosynthetic response of two okra cultivars under salt stress and re-watering

ABSTRACT Two cultivars of okra (Chinese green and Chinese red) were subjected to salt stress (0%, 6%, 12% and 18%) and equal proportions of NaCl and CaCl2 in Hoagland’s nutrient solution and re-watering. Salt stress significantly reduced growth parameters and photosynthetic attributes of both cultivars. Treatment subjected to 18% salt stress caused 90% redundancy in growth parameters of both cultivars compared to control. Re-watering gave a positive response for plant growth of both cultivars in different levels. Chinese green showed better recovery at 6–0% re-watering level and Chinese red showed 12–6% and 6–0%, due to its salt tolerance nature. Considering re-watering water use efficiency and net photosynthetic rate the optimum values of salt tolerance for Chinese green and Chinese red were 8.3% and 12.02%, respectively. The best re-watering degree found as salt stress level ranged from 12.02% to 6% for Chinese red and 8.3% to 2.3% for Chinese green. This study provided a new method for the determination of irrigation time and quantification in crops.

Re-watering: An effective measure to recover growth and photosynthetic characteristics in salt-stressed Brassica napus L.

CHILEAN JOURNAL OF AGRICULTURAL RESEARCH 76(1) JANUARY-MARCH 2016 7 7 Salinity is one of major environmental problem which is limiting the agricultural production. This research was conducted to evaluate the effect of re-watering on Brassica napus L., and determination of an appropriate regime for dilution of salted water by studying photosynthetic and growth response of B. napus to salt stress and subsequent re-watering. Plants were treated with NaCl (Nc1: 2.5, Nc2: 5, Nc3: 10; g L-1); Na2SO4 (Ns1: 2.5, Ns2: 5, Ns3: 10; g L-1) and mixed salts treatments (M1: Nc1+ Ns3; M2: Nc3+ Ns1; M3: Nc2+ Ns2; g L-1) and 0 as control, followed by re-watering. In salt stress phase, maximum reduction in net photosynthetic rate (PN) was noted 79.54%, 80.72%, 84.54%, and 74.84% for Nc3, Ns3, M1 and M2, respectively, under high concentration levels. To maintain PN, carbonic anhydrase (CA) activity was stimulated and kept water status stable under low (Nc1 and Ns1) to medium concentration levels (Nc2, Ns2 and M3), and the decreases in PN under Nc2, Ns2 and M3 were 48.28%, 55.58% and 58.69%, respectively. However, during rewatering phase, growth and physiological parameters were recovered well due to regulation of CA activity under low to medium concentration levels. Relatively as compare to other stress levels more recovery in PN was found after rewatering under medium concentration levels, which were 44.94%, 53.45% and 63.04%, respectively. Though aimed at consideration of high production in B. napus, the best re-watering time was found to be when plants undergo medium concentration levels. Therefore, this study provides a new method for dilution of saline irrigation based on plant physiology.

The influence of three mangrove species on the distribution of inorganic nitrogen and phosphorus in the Quanzhou Bay estuarine wetland soils

This study aims to investigate the effects of region and three regional dominated mangrove species (Avicennia marina, Aegiceras corniculatum and Kandelia candel) on the distribution of inorganic nitrogen and phosphorus. Measurement of the inorganic nitrogen and phosphorus and enzymatic activities was carried out in soils covered by three mangrove species in the Quanzhou Bay estuarine wetlands, a typical coastal wetland in China. Species with a higher biomass in upstream and midstream absorb more nitrogen from soils, and the retention of the available phosphorus in the soils of different regions causes the regional variation of phosphorus. In areas dominated by A. marina, nitrate nitrogen is lower while available phosphorus is higher. Meanwhile, nitrate nitrogen and available phosphorus are higher in the soils covered by K. candel. Moreover, all three species affect the elemental and enzymic stoichiometry. The mangrove species influences the diversity of the elemental and enzymic stoichiometric relationship through differential microenvironments, which induce the biodiversity of wetland ecosystems. Thus, this study may facilitate a better understanding of the transformation ability of mangroves to nitrogen and phosphorus and will therefore be beneficial for providing a basis for the ecological restoration of estuarine wetlands.