Response of Valencia Orange Trees to Some Treatments

Journal of Horticultural Science & Ornamental Plants 10 (3): 167-178, 2018ISSN 2079-2158© IDOSI Publications, 2018DOI: 10.5829/idosi.jhsop.2018.167.178

Corresponding Author: Nadia A.M. Hamed, Horticulture Research Institute, Agricultural Research Centre, Cairo, Egypt.167

Response of Valencia Orange Trees toSome Treatments During Blooming, Fruit Set and Fruit Maturation

Nadia A.M. Hamed

Horticulture Research Institute, Agricultural Research Centre, Cairo, Egypt

Abstract: The present study was carried out during two successive seasons of 2014 - 2015 and 2015 -2016 onvalencia oranges trees budded on sour orange rootstock planted on clay loamy soil with flood irrigation inEl-Qalyobia governorate. Small fruit size is the main factor limiting the marketing of valencia oranges; thus theobjective of the present study is to observe the effects of foliar application with potassium nitrate (1%), GA3

(25 ppm), Amcotone (630 ppm) and nitrophenolate (630 ppm) on fruit set percentage, yield and fruit qualityespecially fruit size of valencia orange trees. On the other hand, leaf chemical properties total phenols, totalindoles, total sugars, total carbohydrates, N, P and K concentrations were determined. Generally, the resultsrevealed that, GA treatment increased fruit set and fruit yield (kg/ tree).While, nitrophenolate treatment3

increased fruit size, fruit weight and improved fruit peel colour. Also, nitrophenolate treatment increased totalphenols and total carbohydrates. Data obtained reflect varied response with varied treatments.

Key words: Valencia orange Potassium nitrate GA Amcotone Nitrophenolate Fruit set Fruit size3

Yield

INTRODUCTION Applying synthetic auxins during the cell division

Valencia is one of the main orange varieties number of fruits and increases the final fruit size bycharacterized by high fruit quality; however, small fruit reducing the competition for carbohydrates betweensize is a common problem in valencia oranges. The price fruitlets [6].of fruit is generally determined by quality factors and Besides plant hormones, other factors are involvedfruit size is one of the main quality factors in fresh fruit in citrus fruit setting, such as the presence of seeds,markets. Consumers prefer larger fruit size; thus, large carbohydrate reserves, photosynthetic rate and mineralvalencia fruit brings higher prices in the export market. nutrition. Positive results have been obtained withRecently, the importance of fruit size in citrus fruits as a potassium nitrate supplementation even with good plantquality parameter has markedly increased. In terms of nutritional status, which is possibly related to the lowerdetermining profitability, fruit size in valencia has ability to mobilize mineral reserves necessary for the fruitbecome as important as yield [1]. Fruit size is inversely set [7].proportional to yield and fruit number [2]. The availability One of the biostimulants is Atonik preparationsof carbohydrates, flower intensity and the competition which contain nitrophenolic compounds naturallybetween them, the competition between fruitlets and fruit occurring in plant tissues [8]. Nitrophenolate (Atonik) isweight have been suggested as the most significant a biostimulant growth consists of three phenolicfactors affecting the final fruit size of citrus fruits. Fruit compounds. Atonik used as stimulant plant growth andsize is a function of cell division and cell enlargement development, particularly generative [9]. Nitrophenolatesprocesses [3]. are found naturally in plants and stimulate plant growth

Several scientific trials showed that the by altering the activity of specific antioxidant enzymes,gibberellins increased the cell wall flexibility by such as superoxide dismutase (SOD), catalase (CAT) andstimulating the synthesis of new cellulose polymers [4]. peroxidase (POX) [10]. Gibberellins could also reduce the senescence of leaves The objective of this study is to evaluate the effect ofand fruits [5]. potassium nitrate, GA , Amcotone and nitrophenolate

stage of fruit development significantly reduces the

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J. Hort. Sci. & Ornamen. Plants, 10 (3): 167-178, 2018

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compound on valencia orange fruit quality especially were subjected to pruning at the autumn of the firstfruit size. Whereas, it was observed in private citrus season. Tree canopy volume was determinate at the firstorchard located in El-Qalyobia Governorate, Egypt, week of March 2015 and last week of September 2015during harvest time that fruits had small size; the size of during 2 season, tree canopy volume was estimatedthe fruit is important, not only because it is a component according to the formula of Obreza [11].of productive yield, but also determines the acceptanceby the consumer. Also, the price of fruit is largely Tree canopy volume (m ) = H × D × 0.5238determined by quality factors whose appreciation is atthe customer’s whims. The customer’s preference for big whereas H= tree height (m), D= diameter of tree peripherysized fruit determines huge differences in market price to (m).a point that the income from the smaller, albeit marketable,fruit is often lower than the actual costs of production and Leaf Area: Ten leaves (fourth or third leaf) of six monthmarketing. Therefore we did trail to try to increase the size old from non-fruiting and non flushing shoots of springof valencia orange fruit. cycle were used to estimate leaf area (cm ).

MATERIALS AND METHODS Flowering and Fruit Set: The leafy and woody

The present study was carried out during two then leafy and woody inflorescences percent weresuccessive experimental seasons 2014-2015 and 2015-2016 calculated. The fruitlets from both leafy and woodyin a private citrus orchard in El-Qalyobia Governorate, inflorescences were counted at the third week of June andEgypt. Fruitfull valencia orange trees (Citrus sinensis then fruit set percentage (%) was calculated according to(L.) Osb.) budded on sour orange rootstock the following equation:(Citrus aurantium), grown on clay loamy soil at 4 × 6 munder flood irrigation system, were used to investigate Fruit set% = (number of fruitlets/ number ofthe influence of foliar spray with treatments under inflorescences) ×100study on the fruit size and quality. Forty five trees(three replicates with three trees at each replicate) Yield: At harvest time (at the second week of March)were subjected to five investigated treatments as fruits of each tree were harvested and the yield wasfollows: Control (sprayed with water), potassium nitrate at estimated as number of fruits and weight in kg. 1% (KNO K O 40%), GA at 25 ppm, Amcotone (contains3, 2 3

0.45% NAA +1.25% NAAM+ 98.30 % other additives) at Fruit Quality: At harvest stage, a representative sample630 ppm (0.6 g / L) and nitrophenolate (Atonik compound of 10 fruits were taken from each tree and the followingcontains sodium A- naphthyl acetic acide1.2%, sodium characters were determined:ortho - nitrophenolate 0.6% sodium para- nitrophenolate0.9%, sodium 5- nitroguaiacolate 0.15% and sodium -2.4- Fruit Physical Properties: Average fruit weight (g),dinitro phenolate 0.15%) at 630 ppm (0.6 g / L). average fruit size (cm ), fruit height and diameter (cm) were

All treatments were applied as foliar spray at full measured and fruit shape index (length/diameter) wasbloom and cell division stages of fruitlets. Whereas, calculated, fruit colour, peel thickness (cm), fruit firmnesspotassium nitrate (1%) treatment was applied three times (l.b/ inches ) and fruit juice percent % (w/ w) wereat cell division, fruit cell expansion and colour break measured.stages, respectively. In addition, rind fruit colour was quantified using

A complete randomized block design was used, each Minolta colorimeter (CR-200, Ramsey, NJ) (Minoltatreatment was replicated three times with three trees for Corporation Instrument Systems) through determining theeach replicate, thus the total number of trees in this three color components (L) lightness, (C) chroma and (H)experiment was 45. Forty five trees (5 treatments x 3 hue angle according to McGuire [12].replicate x 3 trees in each replicate).

Following Parameters Were Investigated acid/100 cm juice), TSS/ acid ratio and vitamin C (ascorbicTree Canopy: The increasing rate of tree canopy (%) was acid as mg/100 ml juice) were determined according tocalculated only in the second season because the trees A.O.A.C. [13].

nd

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inflorescences were counted at the third week of March

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Fruit Chemical Properties: TSS %, acidity % (as mg citric3


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Leaf Chemical Composition: Both total indoles and total Leaf Area: Data represented in Table (1) showed that,phenols were determined in fresh leaves four times nitrophenolate (Atonik) treatment significantly increases(March, June, September and December). Total indoles leaf area at the two experimental seasons when comparedwere determined according to Larsen [14], total phenols with control. were determined according to Swain and Hillis [15]. In this respect, plants treated with a biostimulantTotal sugar (in fresh leaves) and total carbohydrates (Atonik) are characterized by having a higher inhibition(in dry leaves) were determined at September by using 3, of IAA oxidase, which ensures greater activity of5-dinitrosalicylic acid method according to Miller [16]. naturally synthesized auxins [23]. Fully developed plantsN, P and K concentrations were determinate in dried treated with a biostimulant are more advanced inleaves at September of the two experimental seasons. growth and development. A. thaliana plants had anTotal N% was determined by semi-micro Kjeldahl method increased leaf area and better-developed root system. Thedescribed by Plummer [17]. Phosphorus was estimated stimulation of elongative growth, as a result of thecolorimeterically by using the chlorostannous reduced application of nitrophenolat, might be attributed to themolybdophosphoric blue colour method as described by greater concentration and/or activity of auxins [10, 24].King [18]. Potassium concentration was determined by Nitrophenolate stimulates plant growth and development.using the flame photometer. The fresh weight and dry matter and production are

Statistical Analysis: Obtained data was statistically chlorophyll content, supported by an improvement ofanalyzed to determine the analysis of variance and chlorophyll a fluorescence parameters [25].significant differences between means according toSnedecor and Cochran [19]. The multiple comparisons of Flowering and Fruit Set: It is obvious from data inmeans were performed according to Duncan’s multiple Table (1) that, in the second season the highest valuestest range [20] using MSTAT-C software [21]. of leafy inflorescences percentage as well as the lowest

RESULTS AND DISCUSSION with GA and Amcotone treatments when compared with

Tree Canopy: It is clear from data presented in Fig. (1) In this respect, GAs encourage cell division andthat, nitrophenolate treatment produced the highest elongation; increase stalk length, enhance flower and fruitpercentage of tree canopy rate followed by Amcotone volume of fruits, auxins promote shoot elongation, fruittreatment as compared with control which gave the lowest thinning and flower formation[26]. Exogenous treatmentpercentage. The highest percent of tree canopy were with 1-naphthaleneacetic acid, a synthetic auxin analog,obtained with nitrophenolate treatment may be due to seems to promote flowering [27]. increasing nutrients uptake, carbohydrates assimilation, It is clear from data presented in Table (1) that GAstimulate cell elongation, increased leaf area and shoots treatment produced the highest percentage of fruit set atelongation more than other treatments and this matter the two experimental seasons when compared with controlreflected in tree canopy. treatment.

In this respect, biostimulators are a category of In this respect, foliar application of GA increasesrelatively new products of diverse formulations that initial fruit set for weak parthenocarpic species likepositively affect a plant’s vital processes [9]. The use of ‘Orlando’, tangelo, although GA does not improve fruitbiostimulants has been reported to influence the set of most other citrus cultivars [28]. GA stimulates themetabolic processes in plants by stimulating the transition from ovary to fruitlets, since GA deficiencies atsynthesis and enhancement of phytohormones and also this stage result in sever ovary drop. However, GAto improve their photosynthetic activity [22]. The foliar increase in ovaries at anthesis or shortly thereafter inapplication of nitrophenolate was found to improve the both seeded and parthenocarpic cultivars having lowefficiency of the photosynthetic system and chlorophyll abscission rates [29].content in the leaves of Dracocephalum moldavicaplants. Also, nitrophenolate is an environmental-friendly Yield and Fruit Physical Properties: It is clear from datapreparation which has a positive impact on the metabolic presented in Table (2) that, applied treatments showedprocesses of plants [8]. significant increment in yield (kg/ tree), fruit weight as well

increased so that there is a higher leaf area, with rich

values of woody inflorescences percentage were recorded3

control.

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Fig. 1: The effect of treatments on the increasing rate of tree canopy at the second season

Table 1: Effect of treatments on leaf area, leafy, woody inflorescences and fruit set percent of valencia orange treesTreatments Leaf area (cm ) Leafy inflorescences percent (%) Woody inflorescences percent (%) Fruit set (%)2

First seasonControl 18.67 b 81.88 a 18.12 a 17.48 cPotassium nitrate 20.17 b 88.61 a 11.39 a 30.62 abGA 22.06 ab 84.80 a 15.20 a 33.90 a3

Amcotone 24.35 ab 90.36 a 9.64 b 26.68 abNitrophenolate 27.89 a 81.71 a 18.29 a 24.70 bc

Second seasonControl 19.17 d 84.11 b 13.69 a 21.00 cPotassium nitrate 20.58 d 87.69 b 12.3 ab 34.62 abGA 23.44 c 93.58 a 6.42 b 38.15 a3

Amcotone 26.87 b 93.55 a 6.15 b 30.48 bNitrophenolate 29.63 a 88.46 ab 11.54 ab 30.18 bMeans in each colum fallowed by the same letter s did not differ at p<0.05 according to Duncans multiple range tests’

as fruit size for both seasons, as compared with control crops are the applications of plant growth regulators,and the highest significant yield values were recorded for especially gibberellic acid [33].GA treatment. Regarding to fruit weight and fruit size the data3

Similar results were obtained by Baghdady, et al. [30] showed that, the highest significant fruit weight and fruitwho found that, foliar sprays of valencia trees with GA size values were recorded for nitrophenolate followed by3

(15 or 25 ppm) increased fruit set percentage, yield and Amcotone treatment at both seasons. some fruit quality parameters. In this respect, plant biostimulants are known to

In this respect, application of GA (15 ppm) increased improve fruit size, appearance and quality by direct effects3

yield of Clementine mandarin trees when applied at the on fruit growth and development or indirectly byflower bud stage. The yield increment was due to an regulating crop load, tree vigor and canopy architectureincrease in fruit number per tree and in fruit size [3]. The [34]. Nitrophenolate positively affects various processesrole of GA in improving fruit quantity, fruit weight and controlling plant growth, development and productivity.fruit size of Washington navel orange, may be due to its Biostimulant treated plants are more advanced in growth,role in increasing cell elongation [31]. The application of development and accumulate more biomass [35, 36].plant growth regulators, especially gibberellic acid at full Biomass accumulation, both fresh weight and dry matter,bloom, enhances fruit set, yield increment and improving and yield production are stimulated by nitophenolatefruit quality [32]. Plant growth regulators enhance the due to a higher efficiency of the photosynthetic systemrapid changes in physiological and biochemical characters manifested by a higher leaf area, higher chlorophylland improve crop productivity, indicated that among content, greater intensity of photosynthesis and anagricultural practices which may increase the fruit improvement of chlorophyll a fluorescence parametersproduction and improve the quality of several other fruit [25].


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Table 2: Effect of treatments on yield and physical properties of valencia orange fruit during two successive seasonsTreatments Yield (kg/tree) Fruit weight (g) Fruit size (cm ) Fruit ship index Fruit firmness (l.b/inches) Fruit peel thickness (cm) Fruit juice (%)3 2

First seasonControl 40.93 c 123.33 c 139.33 c 1.011 ab 13.52 b 0.301b 48.90 cPotassium nitrate 73.10 a 163.33 b 182.50 b 1.057 a 14.55 b 0.453 a 53.33 bGA 78.04 a 169.83 ab 187.67 b 1.033 ab 16.20 ab 0.401 ab 54.48 b3

Amcotone 54.77 b 179.33 ab 194.00 ab 0.990 b 18.09 a 0.360 ab 57.96 aNitrophenolate 69.33 a 190.67 a 209.00 a 1.034 ab 16.18 ab 0.444 a 53.60 b

Second seasonControl 45.03 d 140.00 c 150.00 c 1.032 a 11.99 b 0.310 b 47.33 cPotassium nitrate 77.30 b 186.67 ab 205.00 b 1.040 a 12.23 b 0.410 ab 54.34 bGA 87.36 a 184.44 b 210.00 b 1.027 a 12.75 b 0.470 a 57.71 ab3

Amcotone 60.62 c 189.17 ab 214.38 ab 1.018 a 16.28 a 0.440 ab 61.48 aNitrophenolate 76.53 b 204.72 a 220.00 a 1.020 a 13.45 ab 0.530 a 55.67 bMeans in each colum fallowed by the same letter s did not differ at p<0.05 according to Duncans multiple range tests. ’

Concerning to the effect of Amcotone on fruit size, compared with control treatment. Moreover, the highestapplying synthetic auxins during the cell division stage of values of juice percent were recorded by Amcotone

treatment at the two experimental seasons.fruits and increases the final fruit size by reducing the These results are in agreement with Nawaz, et al. [42]competition for carbohydrates between fruitlets [6]. on Kinnow mandarin (Citrus reticulata Blanco) as wellThe increase in cell size following NAA application as Farag and Nagy [43] who indicated that, sprayingpossibly indicates its ability to mobilize carbohydrate Washington navel orange with NAA at concentrationuptake and thus enlarge the cells considerably. Another 25 ppm at full bloom increased juice volume as comparedpossibility is that NAA increases the elasticity of the cell with the control. wall, thereby enabling its enlargement due to increasing In this respect, the application of auxin at the onsetthe rate of fruit growth, eventually leading to an increased of cell enlargement stage stimulates cell expansion of juiceyield of large fruit [37]. Fruit size can be improved either vesicles, increasing the vesicle capacity for juiceby increasing carbohydrates availability to fruit or by accumulation [38]. The increase in juice percentage ofincreasing fruit sink strength. Application of synthetic Mandarin may be explained by the fact that hormonesauxins may act in these two ways, depending on the date play a regulating role in the mobilization of metabolitesof treatment. When they are applied during the within a plant and it is well established fact thatphysiological fruit drop they have a thinning effect, developing fruits are extremely active metabolic “sinks”reducing competition for carbohydrates among which mobilize metabolites and direct their flow fromdeveloping fruitlets; while, when applied at the onset of vegetative structure [44].cell enlargement stage fruit sink strength is increased and The percentage of juice is an extremely importantcarbohydrate accumulation in the fruit is enhanced [38]. parameter for its industrial processing, being also relatedThe increase in fruit size may be attributed to the increase to size, which, in turn, although determined by the geneticin cell division and cell elongation caused by NAA and characteristics of each cultivar, can be affected by culturalGA [39]. Application of NAA stimulate cell enlargement practices such as application of plant growth regulators3

in the fruit mesocarp, which in turn, causes an [45, 42].improvement in fruit size and total yield [40]. Regarding to fruit rind colour, the data presented in

Concerning to fruit firmness, data illustrated that, in Table (3) depending mainly on hue angle (H) values,the two experimental seasons Amcotone treatment had regardless of lightness (L) & Chroma (C) values. Our datasignificant increment effect when compared with control. of rind colour at harvest situated generally between the

The results are in agreement with Sharma and hue angle values (60-80), whereas 60 is refers to the deepAnanda [41] who reported that, application of GA at 10 orange, while 80 to greenish yellow.3

ppm and NAA at 5 ppm gave the best quality fruits in The data in Table (3) showed that, nitrophenolate asterms of firmness. well as potassium nitrate treatment decreased significantly

Concerning fruit juice percent, the data revealed that, hue angle (H) values, respectively at the two successiveat the two experimental seasons all treatment showed seasons when compared with control treatment and thissignificant increment for fruit juice percent (w/w) when results means that nitrophenolate and potassium nitrate

fruit development significantly reduces the number of


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Table 3: Effect of treatments on the three colour components lightness (L), chroma (C) and hue angle (H) of valencia orange fruit during two successive seasonsFruit rind colour---------------------------------------------------------------------------------------------------------------------------------------------------

First season Second season----------------------------------------------------------------- --------------------------------------------------------------

Treatments H L C H L CControl 71.10 a 74.17 ab 78.27 a 71.86 a 73.87 a 73.26 aPotassium nitrate 61.44 b 71.50 c 76.48 ab 66.73 b 70.33 b 74.20 aGA 67.35 ab 75.60 a 77.66 a 70.78 ab 74.45 a 72.99 a3

Amcotone 64.91 ab 72.73 bc 70.06 bc 66.80 b 70.57 b 72.17abNitrophenolate 61.34 b 67.82 d 69.81 c 61.46 c 66.36 c 67.00 bMeans in each colum fallowed by the same letter s did not differ at p<0.05 according to Duncans multiple range tests. ’

Table 4: Effect of treatments on chemical properties of valencia orange fruit during two successive seasonsTreatments V.C (mg/100ml juice) TSS (%) Acidity (%) TSS/ acid ratio (%)

First seasonControl 49.00 a 12.16 a 1.187 a 10.24 cPotassium nitrate 49.30 a 11.76 a 0.863 c 13.52 aGA 50.00 a 11.17 a 1.053 ab 11.31 bc3

Amcotone 51.00 a 11.83 a 1.017 abc 12.52 abNitrophenolate 52.90 a 12.33 a 0.943 bc 13.31 ab

Second seasonControl 53.33 a 12.00 b 1.157 a 10.37 cPotassium nitrate 47.41 bc 13.83 a 1.020 b 13.63 aGA 45.67 c 11.50 b 0.997 b 11.59 bc3

Amcotone 50.53 ab 11.58 b 0.924 b 12.54 abNitrophenolate 47.73 bc 12.00 b 0.958 b 12.63 abMeans in each colum fallowed by the same letter s did not differ at p<0.05 according to Duncans multiple range tests’

treatments were improve fruit rind colour and gave deep decreased fruit acidity when compared with control.orange colour fruits with good appearance. This trend The highest values of fruit acidity (%) were obtained byindicated that, both treatments improving the rind fruits control.colour. In this respect, fruit size, appearance, colour, soluble

These results are in agreement with those solids, acidity, vitamin influence by photosynthesis,obtained by Fatma and Abd-Eladl [46] on Olinda translocation of photosynthaters, regulation of stomata,Valencia orange as well as EL Zayat, et al. [47] on valencia activation of enzymes and many other processes.orange trees. Potassium role in water regulation of the plants and

In this respect, potassium is important in fruit tolerance to environmental stresses such as drought,formation and enhances fruit size, flavour and fruit rind excess water, wind, high and low temperature is relatedcolour [48]. Also, plant growth regulators have been used to productivity of the trees and quality of Citrus [50].to manipulate fruit color development in two ways: by Potassium deficiency reduces fruit number and size,enhancing color change for early harvest and by delaying increases fruit creasing, plugging and drop and decreasescolor change concomitant with a delay in rind softening juice soluble solids, acid and vitamin C content [51]. and a reduction in vest and maintaining quality [49]. In addition, fruit juice acidity and juice volume are

Fruit Chemical Properties: Concerning to vitamin c, the substantially higher percent acid than larger fruit anddata revealed that no detected trend was observed by all total soluble solids per fruit is considerably lower in smalltreatments. fruit [3].

It is clear from data presented in Table (4) that,potassium nitrate treatment significantly increased T.SS Leaf Chemical Compositionat the second season as well as T.SS acid ratio at both Total Indoles: The data presented in Figs. (2 and 3)seasons as compared with control. Moreover, the highest indicated that, the highest values of total indoles werevalues of T.SS acid ratio were obtained by potassium obtained by Amcotone followed by potassium nitratenitrate followed by nitrophenolate treatment. A reverse treatment especially in the samples of both September andtrend was obtained by fruit acidity, all treatments December at the two experimental seasons.

greatly affected by fruit size. Small fruit have a


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Fig. 2: The effect of treatments on total indoles concentration of leaves (mg/ g.f.w.) at the first season

Fig. 3: The effect of treatments on total indoles concentration of leaves (mg/ g.f.w.) at the second season

In this respect, the exogenous application of growth Total Phenols: It is clear from the data presented inregulator (NAA) increases their concentration in the Figs. (4 and 5) that, total phenols increased significantlypanicle and antagonises the adverse effects of by nitrophenolate treatment at four dates of samplingendogenous inhibitors [52]. The application of IAA (March, June, September and December) at the two(at 100, 200 and 300 ppm) increased auxin concentration successive seasons as compared with control, withof valencia orange leaves [53]. some exceptions. The highest values of total phenols

Regarding to the effect of potassium nitrate in were obtained by nitrophenolate (especially in theindoles concentration, there is a positive correlation September date sample) and Amcotone treatmentsbetween hormone contents and amount of nutrients like respectively when compared with control.N, P or K absorbed [54]. K O (48%) at a rate of 10 g/l (1%) The increment effect of nitrophenolate on total2

appear to influence some processes involved in the phenols concentration of valencia orange leaves may bemetabolism and activity of endogenous hormones which due to that, this compound is a synthetic biostimulantconsequently affect the structure and the development of composed of three phenolic compounds: sodium para-reproductive organs of squash plants [55]. nitrophenolate PNP(0.3%), sodium ortho- nitrophenolate


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Fig. 4: The effect of treatments on total phenols concentration of leaves (mg/ g.f.w.) at the first season

Fig. 5: The effect of treatments on total phenols concentration of leaves (mg/ g.f.w.) at the second season

ONP(0.2%), sodium5-nitroguaiacolate 5NG (0.1%) and were recorded by all treatments at the two experimentalwater [25]. Also, it was noticed from the data that, seasons when compared with control, with somenitrophenolate treatment increased the carbohydrates exceptions. Moreover, the highest values of sugars wereconcentration and this may be caused the increase in total detected in response to potassium nitrate and GA

treatments at both seasons when compared with controlbiosynthesis overlap the demands for growth the treatment.excess carbon can be used for carbon-based secondary In this respect, potassium is necessary formetabolites such as phenolic compounds [56]. several basic physiological functions, such as sugars

Total Sugars: Data represented in Table (6) division and growth and neutralization of organic acidsrevealed that, significant increases in total sugars [57].

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phenols concentration. Whereas, when carbohydrate

and starch metabolism, synthesis of proteins, normal cell


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Table 5: Effect of treatments on chemical composition of valencia orange leaves during two successive seasonsTreatments Total sugars (mg./ 100 g f.w) Carbohydrates (%) N (%) P (%) K (%)

First seasonControl 22.48 c 1.299 b 1.97 c 0.24 a 1.022 cPotassium nitrate 32.35 a 1.398 ab 2.48 a 0.25 a 1.442 aGA 29.55 ab 1.461 a 2.47 a 0.24 a 1.086 bc3

Amcotone 26.50 bc 1.418 ab 2.38 ab 0.24 a 1.129 bcNitrophenolate 24.70 bc 1.516 a 2.20 b 0.26 a 1.327 ab

Second seasonControl 24.72 c 1.280 b 1.98 b 0.26 ab 1.240 bPotassium nitrate 35.73 a 1.414 b 2.41 a 0.25 ab 1.947 aGA 33.27 ab 1.464 ab 2.43 a 0.25 ab 1.423 b3

Amcotone 32.74 ab 1.455 ab 2.37 a 0.23 b 1.500 abNitrophenolate 29.90 bc 1.621 a 2.09 b 0.29 a 1.491 abMeans in each colum fallowed by the same letter s did not differ at p<0.05 according to Duncans multiple range tests’

Moreover, Mehourachi, et al. [58] stated that, GA Minerals: Data presented in Table (5) revealed that,3

(20 µg/ml) altered the partitioning of assimilate between significant increases in nitrogen concentration werecitrus shoots and roots, increasing the percentage of recorded by all treatments at the both seasons whensoluble sugar and starch of the shoots. These results compared with control, with some exceptions. indicates that gibberellins stimulated growth and In this respect, Addicott and Addicott [65] reportedincreased carbon supply in shoots. Abd-El Wahab [59] that, the effect of GA has at least three important actions,found that, spraying apple nursery plants with GA the first is intensify the ability of organ to work as a3

(250 or 500 ppm) increased plant height and total soluble nutrient sink; secondly, increasing the synthesis of IAAsugars. in plant tissues; the third, it involved in acceleration the

Total Carbohydrates: Concerning to total carbohydrates Moreover, Rubio et al. [66] noticed that, potassiumthe data in Table (5) revealed that, nitrophenolate is of great importance but should be considered astreatment significantly increased the concentration of nutrient supporting nitrogen uptake by plants and itscarbohydrates in the leaves at the two experimental further transformation into plant biomass.seasons. The highest values were obtained by Concerning to phosphorus concentration, the datanitrophenolate followed by GA treatment when revealed that no detected trend was obtained by all3

compared with control. Moreover, the increment of treatments.carbohydrates by nitrophenolate treatment due to the As regarding potassium concentration, the highestincreasing in the leaf area, whereas the leaves are the values were recorded by spraying potassium nitrate asfactory of carbohydrates production. compared with control at two experimental seasons.

In this respect, it is presumed that during the growing In the same concern our data are in harmony withseason flowers and fruits compete with each other and findings by Abd-Allah [67] who found that, potassiumwith vegetative growth for plant metabolites [60]. This percentage in the Washington navel orange leaves wascompetition hypothesis is based mainly on the significantly affected in the first season only since, thecarbohydrate supply and reserves, which regulate fruit set treatments included K HPO increased K value than theand subsequent fruit drop [61]. The application of control as well as Nadia [68] who found that, significantnitrophenolate increases the content of carbohydrates increases in K concentration was recorded by the leaves[62]. of Washington navel orange trees treated with potassium

Also, fruit set and growth requires large amounts nitrate either alone or in combination with growthof carbohydrates, which are provided by the regulators (20 ppm 2,4 -D, 30 ppm GA or 10 ppm BA).photosynthesis of the current season’s leaves and/or It is clear from the data in Table (5) that,by the reserves accumulated during the winter. If the nitrophenolate treatment increased significantly the Nrequirements exceed the capacity of the tree to and K concentrations at the first season. While, theresupply assimilates, fruitlet abscission is triggered, in are non-significant increases in N, K as well as Porder to adjust the final fruit load to carbohydrate supply concentrations were obtained by nitrophenolate treatment[63, 64]. at the second season.

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synthesis of hydrolytic enzymes in aleurone cells.

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In this respect, the mode of action of a 7. Ruiz, R., A.C. García-Luiz, Monerri and J.L. Guardiola,nitrophenolates compounds through increase nutrient 2001. Carbohydrate availability in relation touptake by increase cytoplasmic streaming and fruit-set abscission in citrus. Annals of Botany,prolongation of auxin activity via inhibiting the 87: 805-812.indolylacetic acid and abscissic acid that increases of the 8. Kocira, S., A. Sujak, T. Oniszczuk, A. Szparaga,nitrate reductase activity [25]. Another recent useful M. Szymanek, H. Karakula- Juchnowicz, A. Krawczukbiostimulants product is nitrophenolate, which contains and K. Kupryaniuk, 2018. Improvement of thephenolic compounds and acts by its ability of penetrating photosynthetic activity of Moldavian dragonheadinto plant structure directly and bestows vitality and (Dracocephalum moldavica L.) through foliarcapacity for absorbing and assimilating water and application of a nitrophenolate-based biostimulant.nutrients [47]. BIO Web Conf. Contemporary Research Trends in

Recommendation: In conclusion, it could be reported 9. Calvo, P., L. Nelson and J.W. Kloepper, 2014.that, GA treatment at 25 ppm followed by nitrophenolate Agricultural uses of plant biostimulants. Plant Soil,3

treatment resulted in, increasing fruit set percentage. 383: 3-41. Moreover, GA treatment increased tree yield (kg/ tree) 10. Djanaguiraman, M., D.D. Devi, J.A. Sheeba,3

while, nitrophenolate treatment showed highest fruit size U. Bangarusamy and R.C. H. Babu, 2004. Effect ofand fruit weight. Also, both treatments nitrophenolate as oxidative stress on abscission of tomato fruitswell as potassium nitrate respectively improving fruit rind and its regulation by nitrophenols. Trop. Agric. Res.,colour. With regarding to nitrophenolate effect on fruit 16: 25-36. size and fruit weight in our experiment, we can recommend 11. Obreza, T.A., 1991. Young Hamlin orange treeusing nitrophenolate to increasing the size of valencia fertilizer response in southwest Florida. Proc. Fla.orange fruit. State Hort. Soc., 103: 12-16.

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Response of Valencia Orange Trees to Some Treatments