(Solanum lycopersicum L.) to Application of Potassium and Triacontanol

Response of Tomato (Solanum lycopersicum L.) to Application of Potassium and Triacontanol M.M.A. Khan, G. Bhardwaj, M. Naeem, Moinuddin, F. Mohammad, M. Singh, S. Nasir and M. Idrees Plant Physiology Section, Department of Botany Aligarh Muslim University Aligarh-202 002 India Keywords: lycopene content, ascorbic content, tomato Abstract A number of phytonutrients isolated from fruits, vegetables, beans, grains etc., may have a role in protecting against cancer and cardiovascular diseases and also may delay the effects of ageing. Tomato (Solanum lycopersicum L.) is one of them cultivated widely as an important vegetable crop across the world. The fruit of tomato is a good source of vitamins, particularly ascorbic acid and antioxidants like beta-carotene and lycopene. Lycopene may protect against certain cancers such as prostrate cancer. As far as the growing of tomato is concerned, potassium as a fertilizer increases the lycopene content and other fruit quality characteristics of tomato, while triacontanol (TRIA) is also effective in increasing the yield and quality of tomato fruit. The present study was designed to increase growth, yield and quality of the crop, using both potassium and TRIA alone as well as in combination. The treatments included T0 (K0+deionized water), T1 (K0+TRIA 1 µM), T2 (K30+TRIA 1 µM), T3 (K60+TRIA 1 µM), T4 (K90+TRIA 1 µM) and T5 (K120+TRIA 1 µM). Threeweek old seedlings of tomato were transplanted to pots. The TRIA was sprayed on plants four times at 10 days intervals starting after 40 days of transplantation. Compared to control (T0), all the treatments showed significant increases in the plant height, number of leaves, area per leaf, fresh and dry weights of plant, leafchlorophyll and carotenoids content, leaf-N, P and K contents, fruit yield, fruitascorbic acid and fruit-lycopene contents. The crop responded the best to the treatment combination K90+TRIA 1 µM that enhanced fruit yield, ascorbic acid, lycopene and β-carotenoids content by 57.6, 6.7, 9.5 and 8.3%, respectively over the control. Thus, along with soil application of potassium (90 kg K/ha), very dilute foliar sprays of TRIA (1 µM) could be used successfully for the amelioration of growth, yield and quality of tomato crop. INTRODUCTION Tomato (Solanum lycopersicum L.) is widely cultivated crop in India. It is a good source of lycopene, vitamins, particularly ascorbic acid and antioxidants like β-carotene and lycopene. Epidemiological studies have suggested a protective effect of lycopene (Fig. 1) and lycopene rich tomatoes against various types of cancers. Recent findings suggest that intake of lycopene and other protective compounds found in tomatoes may reduce the risk of prostate cancer. The use of mineral nutrients and growth substances has shown spectacular results both on yield and quality of many vegetable crops. As far as mineral nutrition of tomato is concerned, the effect of potassium (K) is well established. Potassium plays a vital role in growth, plant productivity, metabolism, ionic balance, activation of several enzymes and plant defense systems (Marschner, 2002). Further, managing a balance between vegetative and reproductive growth is a very important part of crop production. Plant growth regulators (PGRs) can help manage this balance. Triacontanol (TRIA) [CH3(CH2)28CH2OH] (Fig. 2) is a straight chain fatty alcohol of 30 carbon atoms and has been recognized as a prominent PGR for various agricultural and horticultural crops (Ries et al., 1977; Ries and Houtz, 1983; Ries, 1985). The present investigation was undertaken to address the question whether we Proc. XIth IS on the Processing Tomato Eds.: R. Pitblado and J. Routledge Acta Hort. 823, ISHS 2009

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could ameliorate the growth, yield and biochemical attributes as well as phytonutrients of tomato by soil-applied potassium and foliar application of TRIA using either alone or in combination. MATERIALS AND METHODS Plant Material and Experimental Design Healthy seeds of a local variety of tomato (Solanum lycopersicum L.) were grown in a net-house at the Botany Department, AMU, Aligarh during winter season of 2005-06. The experiment was conducted in pots according to a simple randomized block design. Five levels of basal K (0, 30, 60, 90 and 120 kg ha-1) and two concentrations of TRIA (0 and 1 µM) were applied in six combinations viz. (i) K0+TRIA 0 µM (control); (ii) K0+TRIA 1 µM; (iii) K30+TRIA 1 µM; (iv) K60+TRIA 1 µM; (v) K90+TRIA 1 µM; and (vi) K120+TRIA 1 µM. Height per plant, number of leaves per plant, area per leaf, fresh and dry weights per plant, chlorophyll and carotenoids contents, leaf-N, P and K contents, weight per fruit, number of fruits per plant, fruit yield per plant and fruit ascorbic acid and lycopene contents, respectively were measured. Prior to seed sowing, a 5 kg homogenous mixture of soil and farmyard manure (5:1) was filled in earthen pots. Soil of the experiment field was sandy loam with pH (1:2) 9.5, E.C. (1:2) 0.50 m mhos cm-1, available N, P and K 108.7, 6.50, and 55 mg kg-1 soil, respectively. The soil samples were analyzed at the Government Soil Testing Laboratory, Quarsi Farm, Aligarh. The seeds were grown in 25 cm diameter pots. Seeds were surface sterilized with 95% alcohol for half an hour and washed with double distilled water. After successful germination, the three-week old seedlings were transplanted to the pots maintaining one plant per pot. Foliar sprays of TRIA were applied in at a 1 µM concentration since it has proved the best treatment for achieving the optimum yield potential in several crop plants (Alexander and Angelov, 1997; Khan et al., 2005). The plants were sprayed four times with TRIA at 10 days intervals. The foliar application of TRIA was started at 40 days after transplanting (DAP). The control plants were sprayed with de-ionized water only. Each treatment was replicated four times. The plants were watered as and when required. Hoeing and weeding was done time to time. Plants were grown under naturally illuminated environmental conditions in the net house. Growth Attributes At 90 DAP (days after planning), four plants from each treatment were uprooted carefully, and washed using tap water. They were surface-dried, thereafter, using a blotting paper and the plant fresh weight was recorded. Later, the plants were dried in a hot air oven at 80°C for 24 h to record dry weight. The height of each plant was measured with the help of meter scale and the numbers of leaves were counted. The area of each leaf was measured using a graph paper sheet and total area per leaf was calculated accordingly. Yield Attributes For yield components, four plants from each treatment were collected at harvest. Fruit numbers per plant were counted. Fruit weight and fruit yield per plant were recorded accordingly. Biochemical and Quality Attributes 1. Leaf Chlorophyll and Carotenoids Content. Total chlorophyll and carotenoids content of leaves were estimated using the method of Mac Kinney (1941) and Ma Clachlan and Zalik (1963), respectively. One hundred mg fresh tissue from interveinal area of leaves was ground using a mortar and pestle in 80% acetone. The suspension was filtered using a filter paper (Whatman No.1). The absorbance of the pigment solution was recorded at 645 and 663 nm for chlorophyll content and at 480 and 510 nm for carotenoids content, using a spectrophotometer (Spectronic 20 D, Milton and Roy, USA). 200

These contents were expressed as mg g-1. 2. Leaf-N, P and K Content. Leaf-nitrogen content was estimated using the method of Lindner (1944). One hundred mg of oven-dried leaf powder was digested in H2SO4 using a digestion tube. Five ml aliquot (peroxide-digested-material) of the solution was taken and 0.5 ml Nessler’s reagent was added. The absorbance of the colour developed solution was recorded at 525 nm, using a spectrophotometer. Leaf-phosphorus content in the same digested material was estimated using the method of Fiske and Subba Row (1925). Leafpotassium content was determined in the same aliquot using a flame-photometer (which works on the principle of emission spectrum). Leaf-N, P and K contents were expressed in terms of percent dry weight. 3. Ascorbic Acid Content. Ascorbic acid content was estimated by the method of Sadasivam and Manickam (1996). Five grams of fruit sample was crushed in 4% oxalic acid using a mortar and pestle. Later the extract was centrifuged at 10,000 rpm and the supernatant was collected. To the filtrate, 10 ml of 40% oxalic acid was added. It was titrated against the dye (Volume V1). The amount of the dye consumed was presumed to be equivalent to the amount of the ascorbic acid present in the sample. To another 5 ml of the supernatant pipetted out and 10 ml of the 4% oxalic acid was added. The titration was done against the dye (Volume V2). Ascorbic acid content was calculated using the following formula. 100 ml × 100 0.5 mg V2 (ml) Ascorbic acid (mg/100 g sample) = ––––––– × ––––––– × –––––––––––– V1 (ml) 5 ml wt. of sample (g) 4. Lycopene Content. Lycopene content in fruits was determined using the method of Sadasivam and Manickam (1996). A few healthy tomatoes were homogenized using a blender. 2.25 g of the pulp was ground with acetone using a mortar and pestle. The extracted material was pooled and transferred to a separating funnel containing 20 ml petroleum ether. The washed petroleum ether contained lycopene content. The absorbance was measured at 503 nm using the spectrophotometer. The lycopene content was calculated using the following formula. 31.206 × absorbance Lycopene content (mg/100 g sample) = –––––––––––––––––––– wt. of sample (g) This method will also extract β-carotene and lutein. Although lycopene is the main carotenoid it can only be accurately determined by HPLC. The process described will only give a measure of the total carotenoid content and as such when referring to the lycopene content in this paper it more accurately refers to total carotenoid content. Statistical Analysis The data were analyzed statistically according to Duncan’s multiple range test (DMRT) using SPSS software, 10th version, U.S.A. Significance of the data was calculated at 5% probability level (p