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some physiological studies on salinity tolerance for some citrus rootstocks rasha arafa anwar ... PDF

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SOME PHYSIOLOGICAL STUDIES ON SALINITY TOLERANCE FOR SOME CITRUS ROOTSTOCKS By RASHA ARAFA ANWAR MOHAMED B.Sc. Agric. Sci. (Cultural Project Management), Higher Institute for Agricultural cooperation, 2003 THESIS Submitted in partial fulfillment of the Requirements for the Degree of MASTER OF SCIENCE In Agricultural Sciences (Plant Physiology) Department of Agricultural Botany Faculty of Agriculture Cairo University EGYPT 2016 ABSTRACT The present study was conducted in the nursery of Horticulture Research Institute, Giza, Egypt under greenhouse conditions on Volkamer lemon (Citrus volkameriana Ten. And pasq.) "VOL" and Cleopatra mandarine (C. reticulata Blanco) "CM” rootstocks seedlings at transplanting stage during 2014 and 2015 seasons. This study aimed to assess the response of seedlings to saline water under some bio-stimulants treatments and it's impact on the growth of the seedlings as well as physiological performance and leaves elements content. The obtained results indicated: i) Both VOL and CM stocks seedlings vegetative growth , physiological performance as well as leaf N, P, K, Mg, Fe, Zn, and Mn concentrations were significantly improved, whereas Na and Cl contents were reduced, when treated with proline, salycilic acid, glycine betaine or humic acid, and irrigated with well water (cont. treat.) or saline water 1500 ppm. ii) Moreover, CM rootstock was more tolerant to high levels of saline water as compared to VOL stock. iii) It can be used of CM stock in citrus seedlings production at low levels of saline water without bio-stimulants applications, and with it's at the high of salinity level up to 1500ppm. On the contrary, VOL can be used in this respect with bio-stimulants substances under saline water conc. 1500 or 2000ppm as well. Keywords: Citrus rootstocks, Volkamer lemon, Cleopatra mandarine, proline, humic acid, Glycine Betaine and Salycilic acid. INTRODUCTION Citrus is the largest horticultural crop in Egypt. It is the major fruit crop industry, during the last few years, and harvested area increased rapidly from year to year ," about 530415 Fed. in 2014"*.Whereas, the fruiting acreage of citrus occupies about 440706 Fed. producing 4,402,180 Tons. It's well known that, agricultural expansion and other uses needs a great amount of available water. But there are many interpretation so for search to find unconventional solutions to this problem by optimizing water resources is to employ these points :a) Raising efficiency of field irrigation system. b) Reuse of agricultural drainage water, c) Searching for about other resources of water and d) the development of research methods in the field of breeding and production assets and plant species tolerant to drought and salinity stress….etc. Additionally, the rapid expansion of irrigated agriculture, efficient use of the limited water resources in arid and semi arid regions is becoming more and more vital. However, water salinity is a major problem due to its negative influence on the yields of many crops. Except for halophytes, water salinity partially inhibits the growth of most plants. *According to Annual Report of Agri. Min. - Egypt (2014). Four reasons that are usually introduced a solely responsible for reduction of plant growth under salts stress conditions. These are briefly the (i) Osmotic stress caused by reducing the availability of external water, (ii) Specific ion effects, (iii) Nutritional imbalance caused by these ion-toxicity effects, and (iv) A combination of any two of the above mentioned factors. Citrus is salt-sensitive. The response to salinity depends on several factors like rootstock–scion combinations, irrigation system, soil type and climate, etc. Changing one or more of these factors (with the same irrigation water) could produce entirely different results. Similar to most other plants, salinity reduces citrus trees’ growth and causes physiological disorders. The increase in the salinity level reduced and delayed seed germination, plant height, stem diameter, number of leaves /seedling, fresh top and root biomass (Singh et al., 2004). Salinity had negative effects on: leaf defoliation, leaf injury, vegetative growth and leaf and root mineral contents (Amen Amal et al., 2008). High salt concentrations caused a great reduction in growth parameters such as fresh and dry weights of shoots and roots (Balal et al., 2011). Salinity had a restrictive effect on rate of root elongation. Roots dry weight for tested rootstocks cvs. had similar trend to that of growth rate by increasing irrigation water salinity concentrations. (Karem et al., 2013). As salinity increased, all measured characteristics of plants after 4.5-month growth except of Na uptake, proline content, and electrolyte leakage decreased ( Zarei and Paymaneh, 2014). In spite of, many citrus rootstocks species suffer a decline in growth while exposed to salinity stress, nevertheless, certain rootstocks as Cleopatra mandarin, Troyer citrange and sour orange are better able to exclude the uptake and translocation of these potentially damaging ions to the shoot and are more tolerant to salinity. Whereas, the relative tolerance of these various rootstocks appeared to be due primarily to their ability to exclude Na and Cl from the leaves, (Mickelbart et al., 2007). Bio-stimulant application "such as humic acid , amino acids and related products have great impacts on plant growth. Its involving increase nutrient uptake, tolerance to drought and extremes temperature, activate of beneficial soil microorganisms, as well as facilitate the availability of soil nutrients particularly in alkaline soils and those have low organic matter (Russo, 1959 and Shaban and Mohese, 2009). Also, humic materials may increase root growth in a similar manner to auxins (, O'Donnell, 1973, Tattini et al. 1991 and Senaratna et al. 2000). Moreover, bio-stimulants can enhance the yield and fruit quality of citrus and it becomes a positive factor to minimize utilization of inorganic and chemical fertilizers. It is safe for human and environment and using them was accompanied with reducing the great pollution occurred on our environment as well as for producing organic foods for export. It can serve as useful components of integrated plant nutrient supply systems which help in increasing crop productivity by increasing soil organism's activity and so increasing availability of nutrient elements and consequence their uptake, moreover these substances can stimulate plant growth through hormonal action or antibiosis. Generally, the current study, present information and data regarding the effect of some bio – stimulants applications on growth and nutrient uptake of Volkameriana and Cleopatra mandarin citrus rootstocks seedlings under salinity conditions at transplanting stage, aiming to reduce the damage of salinity on the growth of citrus seedlings. REVIEW OF LITERATURE 1. Vegetative growth of citrus seedling Russo (1959) mentioned that, producing citrus seedlings needs suitable rootstock, fertile soil media and good agriculture management such as : Volkamer lemon (Citrus volkameriana) which is used as a rootstock for citrus, due to its tolerance and its acceptable resistance of a large scale of citrus diseases. Moreover, it induces the vigor of citrus seedlings and consequently reduce the time needed in the nursery for seedling production . Marco (1977) reported that, Rangpur lime and Cleopatra mandarin rootstocks are more resistant to salinity than Ponicitrus trifoliata rootstock and Sour orange was more tolerant to fluctuations in soil water content than Citrus lime. Jooika and Singh (1979) stated that, Rangpur lime and Cleopatra mandarin were the most tolerant when grown in pots with soil and salts conditions of 2.3 -9.9 mmhos/cm and their growth was assessed after 120 days. Rokba et al. (1979) found that, Cleopatra mandarin appeared to be the most tolerant variety to salinity stress, followed by Poor man orange rootstock, but Volkamer lemon rootstock was intermediate . Grieve (1983) concluded that, the most salt tolerant rootstocks were Cleopatra mandarin, Rangpour lime ,Sweet orange, Carrizo Citrange and Troyer citrange, respectively. Caro et al. (1979) found that, trunk" diameter and height" of the aerial parts, weight of roots and the shoot / root ratio of Troyer citrange, Cleopatra mandarin and Sour orange rootstocks were decreased with increasing salinity of irrigation water. Ragab (1979) mentioned that branches length and dry weight of leaves, stem and roots of Valencia orange budded on Sour orange rootstock were progressively depressed with increasing salinity levels. Rokba et al. (1979) stated that, growth measurements for Sour orange, Cleopatra mandarin and Rough lemon decreased with increasing different salinity levels in irrigation water. They added that excessive accumulation of chloride causes leaf-burn, shoot dieback, defoliation and finally, the death of entire plant. In addition, the degree of severity and time in which the symptoms appeared varied with the variety and salt level used for irrigation water. Mylonas and McCants (1980) reported that, tobacco (Nicotiana tabcum) plants grown on filter paper saturated with humic acid solutions had higher root numbers and total root length than plants grown on filter paper saturated with nutrient solution or deionised water. Rauthan and Schnitzer (1981) reported that, humic substances positively affected plant growth by increasing soil aggregation, aeration and permeability. Schettel and Balke (1983) found that, SA produced in the rhizomes here of some plants played the role of an allelopathic chemical and inhibited the growth of the surrounding plants. Abdel Messih et al. (1984) found that, growth rate of some citrus rootstock was depressed by increasing salinity levels. Dasberg et al. (1985) indicated that, salinity of irrigation water had no effect on Shamouti oranges plant growth in the 1st season, however, in the 2nd season, the increase in main branch diameter was retarded by the highest salinity treatment. Sherif (1985) mentioned that, growth rate as well as dry weights of leaves, shoots and roots of Sour orange, Cleopatra mandarin, Rough lemon and Rangpur lime rootstock were depressed by increasing the salinity level in irrigation water. Zekri and Parsons (1990) found that, salinity treatments affected total leaf area and seedling height of Sour orange and Cleopatra mandarin citrus rootstock grown in fine sand under greenhouse conditions by 44-55% with all salt treatments. In additions, irrigated water 40 mM NaCl reduced Sour orange seedlings root and shoot dry weights by approximately 30%, but did not induce leaf necrosis. Montaser et al. (1993) indicated that, the increase in salts concentration proportionally decreased mango seedlings height; stem thickness, total number of leaves, leaf area and dry matter of leaves, stem and roots. Syvertsen et al. (1993) mentioned that, the high salinity irrigation water reduced tree canopy growth of 6-year-old 'Valencia' orange trees budded on either Carizo citrange (CC) or sour orange (SO) rootstocks. Vallini et al. (1993) reported that, plants treated with 300 mg kg-1 of humic acid had the heaviest weight of both fresh and dry shoots; however, doses of 3000 mg kg-1 were highly photoxic and inhibited the growth of laurel plant. Combrink et al. (1995) studied : i) the occurrence of Cl- toxicity symptoms on the leaves, they indicated that Vlokamer lemon rootstock was the most tolerant to Cl, followed by Roman lemon.ii) Reduced root and shoot DM with increased chloride concentration, they obtained that VOL was the most tolerant rootstock followed by RLE. El-Desouky and Atawia (1998) mentioned that Volkamer lemon and Rangpur lime rootstocks showed greater salt tolerance than sour orange and Cleopatra mandarin rootstocks. Whereas, the maximum tolerable salinity level was determined to be 4000 ppm. Anjum et al. (2001) reported that, under salinity stress conditions Cleopatra mandarin and Gadadehi proved to be the most tolerant, while Kharnakhatta was the least tolerant one and Jattikhatti, Jambherikhatti and Yuma citrange were moderately salt tolerant. Liu and Cooper (2002) showed that, salinity had less effect on root growth than top growth, humic acid treatment enhanced root growth of salt stressed plants and improved salinity tolerance by neither increased uptake of the mineral nutrients inhibited by salinity, nor decreased uptake of the nutrients which were excessive and toxic in the salinity solution. Phanuphong and Gregory (2003) showed that, the application of humic acid has a positive influence in promoting overall tree vigor. Treated trees were larger and the root system was better developed than the untreated trees. Other study found that, humic substances have a very profound influence on the growth of plant roots. When humic acids and fulvic acids are applied to the soil, enhancement of root initiation and increased root growth may be observed (Pettit, 2004). The stimulatory effects of humic substances have been directly correlated with enhanced uptake of macronutrients, On the contrary, Pablo and William (2003) stated that, humic acid did not affect papaya transplant growth (shoot dry weight, shoot height, leaf number, leaf area and trunk diameter). Singh et al. (2004) reported that, the increase in the salinity level reduced plant height, stem diameter and number of leaves per seedling. The reduction in these parameters was lowest in C. limonia, followed by C. jambhiri and P. trifoliata., C. limonia was tolerant, C. jambhiri was moderately tolerant, and P. trifoliata was susceptible to salinity. On The response of C. jambhiri, C. limonia and Poncirus trifoliata rootstocks to various levels of soil salinity conditions. Camara-Zapata et al. (2004) noticed that, Salinization reduced plant dry weight more in sour orange than in Cleopatra mandarin plants. Growth of both cultivars was not recovered totally in the relief period, since relative growth rates of recovered plants were lower than

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betaine or humic acid, and irrigated with well water (cont. treat.) or saline as Cleopatra mandarin, Troyer citrange and sour orange are better.
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