Effect of different levels of foliar application of potassium on Hysun-33 and Ausigold-4 sunflower (Helianthus annum L.) cultivars under salt stress.
The demand for oil seeds has increased several times for the last few years but the acreage cannot be increased due to the increasing competition with major cereal crops. Sunflower is one of the four major oilseed crops (soybean, peanut, rapeseed and sunflower) grown for edible oil in the world, which is cultivated on about 23.31 million hectares (mha) all over the world. In Pakistan, it is grown on about 0.363 mha (MINFA, 2010). Oil seed crops are mostly grown on marginal lands and the productivity of oilseed crops is much less on saline soils because salinity exerts a number of adverse effects on plants including osmotic effects, ion toxicity and nutritional imbalance resulting in reduced growth and yield (Riaz et al, 2008; Munns, 2005; 2002; Ashraf, 2004). High external [Na.sup.+] inhibits the uptake of other nutrients particularly [K.sup.+], by interfering with the transport mechanism at the root plasma membrane such as [K.sup.+] selective ion channels (Tester and Davenport, 2003). Potassium ions constitute the most important macronutrients taken up by plants in salt-affected soils. [Na.sup.+]competes with [K.sup.+]and reduces its uptake and causes potassium deficiency (Carden et al, 2003). The capacity of plants to counter balance salt stress depends largely on the status of their K nutrition because it plays a vital role in many cell processes such as enzyme activity, cell turgor, regulation of stomatal movement and maintenance of osmotic pressure (Shabala et al., 2005; Shabala, 2003). Potassium increases the protein content, improves the efficiency of water use and produces resistance to diseases and insects. However, salinity stress greatly reduces the uptake and translocation of nutrient ions like [K.sup.+] and [Ca.sup.2+] (Nawaz et al., 2002; Rangel, 1992). These problems can be tackled by growing the tolerant crops i.e., the crops able to produce high yields on such marginal lands (Sandhu and Qureshi, 1986). Salt-affected soils comparatively demand more nutrients for plant growth and optimum yield. The major fraction of potash fertiliser directly applied to soil gets fixed with clay fraction and becomes unavailable to crop plants (Ali et al., 2005). Further, the price of K fertilisers is increasing and is becoming unaffordable to farmers (NFDC, 2005). Keeping in view the economic importance of sunflower as oil seed crop, hydroponic experiment was conducted to test foliar application of [K.sub.2]S[O.sub.4] using two sunflower cultivars (Hysun-33 and Ausigold-4) under salt stress during the growing season 2011, at Soil Salinity Laboratory, Land Resources Research Institute, National Agricultural Research Centre (NARC), Islamabad, Pakistan.
Materials and Methods
Nursery of both cultivars was raised in sand at NARC and 10-day old one seedling per hole was transplanted in each pot having four holes per pot lid. Half strength Hoagland's nutrient solution was filled in each pot and after the seedling establishment; a salt stress of 60 mM (6 dS/m) was developed artificially. The treatments were 0, 2 and 4 % [K.sup.+] as [K.sub.2]S[O.sub.4] foliar application. Crop was grown up to 4 weeks and data on fresh biomass per plant was recorded at the time of harvest. Plant samples were dried in oven at 60 [degrees]C to a constant weight and the dry matter yield was recorded. Ground plant samples were digested in diacid (perchloric-nitric acid 2:1 ratio) mixture (Rhoades, 1982) to estimate Na and K by atomic absorption spectrophotometer (Perkin-Elmer, 4000). The experiment was set up in completely randomised design (factorial) with four replicates. The data obtained were subjected to statistical analysis using MSTAT-C and the treatment means were compared using Duncan's Multiple Range (DMR) test (Gomez and Gomez, 1984).
Results and Discussion
The fresh and dry weights of two sunflower cultivars are given in Table 1-2. Application of varying levels of [K.sub.2]S[O.sub.4] improved the fresh and dry weights of sunflower under both normal and saline conditions. However, the highest increase in fresh and dry weight of control and stressed plants was observed with 2% foliar application of K as [K.sub.2]S[O.sub.4]. Sultana et al. (2001) concluded that foliar application of nutrient solutions partially alleviates the adverse effects of salinity and yield related components through mitigating the nutrient demands of salt-stressed plants. Further increase in the level of K application did not improve fresh and dry weights of salt stressed and unstressed plants. The concentrations of [Na.sup.+] and [K.sup.+] in sunflower tissue are presented in Table 3-4. Salt stress suppresses the uptake of K from soil but foliar application of [K.sub.2]S[O.sub.4] improved the growth of sunflower cultivars under both control and saline conditions. However, the highest increase of control and stressed plants was observed when 2% K applied as a foliar spray. These findings are supported with the results of Kaya et al. (2001a). They suggested that supplementary P and K can reduce the adverse effects of high salinity on plant growth and physiological development. Further increase in the level of K application did not further improve the growth of salt stressed and unstressed plants.
The growth medium salts caused a marked reduction in growth of sunflower. However, application of potassium sulphate improved the growth of sunflower plants under both non-saline and saline conditions. Kaya et al. (2001b) suggested that sodium concentration in plant tissues increased in both cultivars of strawberry in the high NaCl treatment. Concentrations of P and K were in the deficient range in plants grown at high NaCl and these deficiencies were corrected by foliar application of these nutrients under salt stressed conditions. These results can be correlated to the findings that exogenous application of potassium offset the adverse effects of salinity and improved the growth attributes in different crop plants eg., strawberry (Kaya et al., 2001c), cucumber and pepper (Kaya et al., 2003). Similarly, in a study on Lagenaria siceraria, Ahmad and Jabeen (2005) reported that foliar application of potassium nitrate counteracted the salt induced growth inhibition in rice plants. However, in the present study 2% [K.sub.2]S[O.sub.4] was found to be effective in minimizing the adverse effects of salt stress on sunflower plants.
Application of varying levels of K improved the fresh and dry mass of sunflower under both control and saline conditions. However, the highest increase in fresh and dry weight of controlled and stressed plants were observed when 2% K was applied as foliar spray. Further, 2% K foliar application increased the [K.sup.+] concentration of plant tissues grown under normal as well as salt stress conditions resulting in more biomass production. Nevertheless, the foliar application has no significant effect on both genotypes.
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(received March 20, 2012; revised May 8, 2013; accepted May 27, 2013)
Muhammad Arshadullah *, Arshad Ali, Syed Ishtiaq Hyder, Imdad Ali Mahmood and Bdar-uz-Zaman
Land Resources Research Institute, National Agricultural Research Centre, Islamabad-45500, Pakistan
* Author for correspondence; E-mail: firstname.lastname@example.org
Table 1. Fresh biomass (g/plant) of sunflower as affected by foliar application of K Treat- Salinity levels (dS/m) ments 0 Hysun-33 Ausigold-4 Mean Control 1.26c 1.28c 1.27C 2% K 1.62a 1.55a 1.59A 4% K 1.58ab 1.37b 1.48AB Mean 1.49 1.4 1.35B Treat- Salinity levels (dS/m) ments 6.0 Hysun-33 Ausigold-4 Mean Control 1.17c 1.19b 1.18C 2% K 1.55a 1.76a 1.67A 4% K 1.33b 1.77a 1.57AB Mean 1.57A Means followed by different letter (s) within the columns differ significantly at 1% level of significance. Table 2. Dry weight of sunflower (g/plant) as affected by foliar application of K Treat- Salinity levels (dS/m) ments 0 Hysun-33 Ausigold-4 Mean Control 0.04 0.05 0.045B 2% K 0.07 0.06 0.065A 4% K 0.05 0.07 0.060A Mean 0.05 0.06 0.06 Treat- Salinity levels (dS/m) ments 6.0 Hysun-33 Ausigold-4 Mean Control 0.04 0.05 0.06 0.045C 2% K 0.07 0.08 0.075A 4% K 0.06 0.07 0.065B Mean 0.07 Means followed by different letter (s) within the columns differ significantly at 1% level of significance. Table 3. Na Concentration (%) in sunflower tissue at harvesting Treat- Salinity levels (dS/m) ments 0 Hysun-33 Ausigold-4 Mean Control 0.30bc 0.43b 0.35AB 2% K 0.43b 0.43b 0.43A 4% K 0.80a 0.53a 0.44A Mean 0.51 0.45 Treat- Salinity levels (dS/m) ments 6.0 Hysun-33 Ausigold-4 Mean Control 0.43bc 0.58bc 0.50BC 2% K 0.53b 0.65b 0.59B 4% K 0.73a 0.83a 0.78A Mean 0.56B 0.68A Means followed by different letter (s) within the columns differ significantly at 1% level of significance. Table 4. K Concentration (%) in sunflower tissue at harvesting Treat- Salinity levels (dS/m) ments 0 Hysun-33 Ausigold-4 Mean Control 2.88c 2.40bc 2.64C 2% K 4.18b 2.95b 3.56B 4% K 6.50a 3.43a 4.96A Mean 4.53A 2.92B 4.43A Treat- Salinity levels (dS/m) ments 6.0 Hysun-33 Ausigold-4 Mean Control 3.73bc 2.70c 3.21C 2% K 3.98b 3.43b 3.70B 4% K 5.53a 4.68a 5.10A Mean 3.60B Means followed by different letter (s) within the columns differ significantly at 1% level of significance.
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|Author:||Arshadullah, Muhammad; Ali, Arshad; Hyder, Syed Ishtiaq; Mahmood, Imdad Ali; Bdar-uz-Zaman|
|Publication:||Pakistan Journal of Scientific and Industrial Research Series B: Biological Sciences|
|Date:||Mar 1, 2014|
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