Malus Seedlings With Different Salt Tolerance Biology Essay

Plants of Na+ exclusion in barley, maize, rice and wheat were believed to resorb Na+ from the xylem and accumulate in the roots Nassery and Baker, 1972 ; Yeo et al. , 1977 ; Yeo and Flowers, 1982 ; Lu and Wang, 1993 ; Yang et al. , 2002, meanwhile, the roots could besides squeeze out Na+ to the medium. Since the downward conveyance of Na+ existed in bast ( Lessani and Marschner, 1987 ) , the upward conveyance of Na+ in xylem could be re-transported to roots through landscape orientation conveyance of root base ( Jacoby, 1979 ) or through downward conveyance of shoot foliages ( Levi, 1970 ) . Split-roots experiment of Phaseolus vulgaris showed that the most of Na were downward transported to the chief roots and the most of Na geting in the chief roots were extruded to the medium ( Jacoby, 1979 ) . Isotope tracer of 22Na besides showed that the roots of wheat had higher Na+ bulge capableness under salt emphasis, and the Na+ bulge capableness of roots even stronger with the addition of NaCl concentration ( Wang et al. , 2008 ) .

The recretohalophytes had salt secretory organ or salt vesica to egest Na+ ( Zhou et al. , 2001 ) , such as Limonium bicolor had salt secretory organ, Glycine soy and Atriplex spongiosa had salt vesica. Salt elimination played an of import function in modulating Fe balance, keeping osmotic presser and bettering salt tolerance ( Zhang et al. , 2003 ) . Although salt-tolerant Citrus reticulata Blanco had no salt secretory organ or salt vesica, it could besides egest Na+ from cell clearance and pore ( Liu and Zhang, 1994 ) . Therefore, salt in workss could either be extruded from roots or excreted from foliages. In this article, we aimed to analyze the Na+ bulge of roots and Na+ elimination of foliages in Malus seedlings to supply the theory footing for Na+ exclusion mechanism of fruit trees.

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2. MATERIALS AND METHODS

2.1. Plant stuff cultivation

Salt-sensitive assortment Malus baccata ( L. ) Borkh. , in-between salt-tolerant assortment Malus xiaojinensis Cheng et Jiang and salt tolerant assortment Malus zumi Mats of Malus seedlings were tissue civilization seedlings. After roots growth, tissue civilization seedlings were cultivated in alimentary solution, which were ventilated continuously. Malus seedlings were placed in the greenhouse, day/night temperature averaged 26 a„?/18 a„? , and day/night comparative humidness averaged 50 % /65 % . Light strength was about 800 i?­moli?-m-2i?-s-1 and was 12 hours photoperiod.

2.2. Split-roots experiment

Rootss of Malus seedlings were separated into two similar parts and set into two plastic vass. One fictile vas was added with alimentary solution and another fictile vas was added NaCl solution with concentration of 50, 100 and 150 mmol/L. Both alimentary and NaCl solution were all ventilated continuously. 5 yearss subsequently, took alimentary solution and roots for standby.

2.3. Na+ elimination experiment

Washing the salt of foliages surface with dual distillment H2O. Concentration of NaCl emphasis was 50, 100 and 150 mmol/L. 10 yearss subsequently, took immature foliages, mature foliages and old foliages to weigh rapidly, so washed the foliages with dual distillment H2O of 100 milliliter.

2.4. Measurement of Na+ content

Puting dry and grind stuff ( 10 milligram ) of roots and foliages in furnace ( 500 a„? ) for 20 hours, adding 1 to 2 trickle ( s ) of dense azotic acid to fade out ash, repairing the volume to 50 milliliters, rocking equally and mensurating Na+ content with “ Hitachi Ziˆ­8000 Atomic Spectrometer ” . Na+ content of solution was measured with same instrument.

2.5. Calculation of Na+ bulge capableness and Na+ elimination capableness

Salt-sensitive assortment Malus baccata ( L. ) Borkh. , in-between salt-tolerant assortment Malus xiaojinensis Cheng et Jiang and salt tolerant assortment Malus zumi Mats of Malus seedlings were tissue civilization seedlings. After roots growth, tissue civilization seedlings were cultivated in alimentary solution, which were ventilated continuously. Malus seedlings were placed in the greenhouse, day/night temperature averaged 26 a„?/18 a„? , and day/night comparative humidness averaged 50 % /65 % . Light strength was about 800 i?­moli?-m-2i?-s-1 and was 12 hours photoperiod.

3. RESULTS AND DISCUSSION

3.1. Consequence of NaCl emphasis on Na+ bulge capableness of roots in Malus seedlings

With the addition of NaCl emphasis concentration, the Na+ bulge capableness of roots in M. xiaojinensis and M. baccata decreased, and that in M. baccata decreased more evidently, while that in M. zumi evidently increased by grades ( P & lt ; 0.01 ) . Under the same NaCl emphasis, the Na+ bulge capableness of roots in M. zumi was evidently higher than that in M. xiaojinensis ( P & lt ; 0.01 ) and M.xiaojinensis evidently higher than that in M. baccata ( P & lt ; 0.01 ) . The mean Na+ bulge capableness in M.xiaojinensis was 1.58 creases as that in M. baccata and M. zumi 2.87 creases as that in M. baccata ( Figure 1 ) . It indicated that the higher Na+ bulge capableness of roots in salt-tolerant assortments would expeditiously cut down the Na+ content of shoot foliages and more salt tolerant.

Figure 1: Consequence of NaCl emphasis on Na+ bulge capableness of roots in Malus seedlings

Datas are average A± SE ( n = 3, *P & lt ; 0.05, **P & lt ; 0.01, the same as below )

3.2. Consequence of NaCl emphasis on whole recirculation sum of Na+ in Malus seedlings

Sing from Figure 2, the whole recirculation sum of Na+ in 3 Malus seedlings all increased by grades with the addition of NaCl emphasis concentration, and that in M. zumi increased the most ( P & lt ; 0.01 ) . Under the same NaCl emphasis, the whole recirculation sum of Na+ in M. zumi was evidently higher than that in M. xiaojinensis ( P & lt ; 0.01 ) and M.xiaojinensis evidently higher than that in M. baccata ( P & lt ; 0.01 ) . The mean whole recirculation sum of Na+ in M. xiaojinensis was 1.35 creases as that in M. baccata and M. zumi 1.94 creases as that in M. baccata. It showed that the whole recirculation sum of Na+ in salt-tolerant assortments were evidently higher than that in salt-sensitive one ( Figure 2 ) , which would expeditiously cut down the Na+ content of shoot foliages in salt-tolerant assortments.

Figure 2: Consequence of NaCl emphasis on whole recirculation sum of Na+ in Malus seedlings

3.3. Consequence of NaCl emphasis on Na+ bulge per centum of whole recirculation of roots in Malus seedlings

With the addition of NaCl emphasis concentration, the Na+ bulge per centum of whole recirculation of roots in M. xiaojinensis and M. baccata evidently decreased ( P & lt ; 0.05 and P & lt ; 0.01 ) , while that in M. zumi somewhat increased. Under NaCl stress concentration of 50 mmol/L, the Na+ bulge per centum of whole recirculation of roots in M. zumi had no obvious difference with that in M. xiaojinensis ( P & gt ; 0.05 ) , but that in M. zumi and M. xiaojinensis all evidently higher than that in M. baccata ( P & lt ; 0.05 ) . Under NaCl stress concentration of 100 and 150 mmol/L, the Na+ bulge per centum of whole recirculation of roots in M. zumi was evidently higher than that in M. xiaojinensis ( P & lt ; 0.05 and P & lt ; 0.01 ) and M. xiaojinensis evidently higher than that in M. baccata ( P & lt ; 0.05 ) ( Figure 3 ) . In split-roots experiment of Jacoby ( 1979 ) , approximately 11 % of captive Na was released to the mediums by chief roots. This split-roots experiment showed that the mean Na+ bulge per centum of whole recirculation of roots in M. zumi, M. xiaojinensis and M. baccata was 42.23 % , 34.41 % and 30.03 % severally ( Figure 3 ) , that in salt-tolerant assortments were evidently higher than that in salt-sensitive one, which made roots of salt-tolerant assortments have adequate volume to take in Na+ from landscape orientation conveyance of root base and downward conveyance of shoot foliages.

Figure 3: Consequence of NaCl emphasis on Na+ bulge per centum of whole recirculation of roots in Malus seedlings

3.4. Consequence of NaCl emphasis on Na+ elimination capableness of foliages in Malus seedlings

Salt elimination could cut down Na+ content of shoot and better salt tolerance ( Zhang et al. , 2003 ) . Sing from Figure 4, the Na+ elimination capableness of foliages all increased with the addition of NaCl emphasis concentration, and that of immature and old foliages increased more than that of mature leaves did. The Na+ elimination capableness of immature and old foliages was evidently higher than that of mature 1s, and it was even evidently under NaCl stress concentration of 100 and 150 mmol/L ( P & lt ; 0.01 ) . Under the same NaCl emphasis, the Na+ elimination capableness of immature and old foliages in M. zumi and M. xiaojinensis was evidently higher than that in M. baccata. It indicated that the Na+ elimination capableness of shoot foliages in salt-tolerant assortments was evidently higher than that in salt-sensitive one, which would benifit to cut down the Na+ content of shoot foliages in salt-tolerant assortments and more salt tolerant.

Figure 4: Consequence of NaCl emphasis on Na+ elimination capableness of foliages in Malus seedlings

3.5. Consequence of NaCl emphasis on whole Na+ elimination capableness in Malus seedlings

With the addition of NaCl emphasis concentration, the whole Na+ elimination capableness in M. xiaojinensis and M. baccata all evidently increased by grades ( P & lt ; 0.05 and P & lt ; 0.01 ) , and that in M. zumi increased the most ( P & lt ; 0.01 ) . Under the same NaCl emphasis, the whole Na+ elimination capableness in M. zumi was evidently higher than that in M. xiaojinensis ( P & lt ; 0.01 ) and M. xiaojinensis evidently higher than that in M. baccata ( P & lt ; 0.01 ) ( Figure 5 ) . It showed that the whole Na+ elimination capableness in salt-tolerant assortments were evidently higher than that in salt-sensitive one.

Figure 5: Consequence of NaCl emphasis on whole Na+ elimination capableness in Malus seedlings

3.6. Consequence of NaCl emphasis on Na+ elimination per centum of whole Na+ in Malus seedlings

Sing from Figure 6, the Na+ elimination per centum of whole Na+ of old foliages all evidently increased with the addition of NaCl emphasis concentration ( P & lt ; 0.05 and P & lt ; 0.01 ) and that of immature foliages evidently increased under 150 mmol/L NaCl emphasis ( P & lt ; 0.05 and P & lt ; 0.01 ) ; nevertheless, that of mature foliages showed no obvious alteration with the addition of NaCl emphasis concentration ( P & gt ; 0.05 ) . The Na+ elimination per centum of whole Na+ of immature and old foliages was evidently higher than that of mature foliages under NaCl stress concentration of 100 and 150 mmol/L ( P & lt ; 0.01 ) . Under the same NaCl emphasis, the Na+ elimination per centum of whole Na+ of immature and old foliages in M. zumi and M. xiaojinensis was evidently higher than that in M. baccata ( P & lt ; 0.01 ) , and that of immature foliages was similar with that of old foliages in M. xiaojinensis ; nevertheless, the Na+ elimination per centum of whole Na+ of immature foliages was the highest in M. zumi. The mean Na+ elimination per centum of whole Na+ in M. zumi, M. xiaojinensis and M. baccata was 13.01 % , 11.02 % and 8.11 % severally, that in salt-tolerant assortments were evidently higher than that in salt-sensitive one.

Figure 6: Consequence of NaCl emphasis on Na+ elimination per centum of whole Na+ in Malus seedlings

4. Decision

The salt-tolerant Malus seedlings had higher Na+ bulge capableness of roots and Na+ elimination capableness of foliages than the salt-sensitive one, which made the Na+ content of shoot even less and more salt resistant in salt-tolerant Malus seedlings.

Recognitions

The writers would wish to admit the fiscal support from National Natural Science Foundation ( 39740027 ) , Peoples Republic of China, and would wish to admit the Particular Fund for Agro-scientific Research in the Public Interest ( 201203075 ) and Key Laboratory of Biology and Genetic Improvement of Horticultural Crops ( Nutrition and Physiology ) , Ministry of Agricultural, Peoples Republic of China.