Ali, M., Harhash, M., Awad, R., Abd El-Azeem, H. (2021). Spraying Marine Algae Extracts and Some Growth Regulators to Enhance Fruit Set, Yield and Fruit quality of Winter Guava. Journal of the Advances in Agricultural Researches, 26(4), 319-327. doi: 10.21608/jalexu.2021.105537.1019
Mahmoud Ahmed Ali; Mohamed Mohamed Harhash; Rehab Mohamed Awad; Hassan Abd El-Azeem. "Spraying Marine Algae Extracts and Some Growth Regulators to Enhance Fruit Set, Yield and Fruit quality of Winter Guava". Journal of the Advances in Agricultural Researches, 26, 4, 2021, 319-327. doi: 10.21608/jalexu.2021.105537.1019
Ali, M., Harhash, M., Awad, R., Abd El-Azeem, H. (2021). 'Spraying Marine Algae Extracts and Some Growth Regulators to Enhance Fruit Set, Yield and Fruit quality of Winter Guava', Journal of the Advances in Agricultural Researches, 26(4), pp. 319-327. doi: 10.21608/jalexu.2021.105537.1019
Ali, M., Harhash, M., Awad, R., Abd El-Azeem, H. Spraying Marine Algae Extracts and Some Growth Regulators to Enhance Fruit Set, Yield and Fruit quality of Winter Guava. Journal of the Advances in Agricultural Researches, 2021; 26(4): 319-327. doi: 10.21608/jalexu.2021.105537.1019
Spraying Marine Algae Extracts and Some Growth Regulators to Enhance Fruit Set, Yield and Fruit quality of Winter Guava
1Faculty of Agriculture SabaBasha- Plant Production Department
2Faculty Of Agriculture Sababasha - Alexandria Univerisity
Abstract
This experiment was carried out during 2018 and 2019 seasons to investigate the effect of spraying marine algae extracts (Ascophyllum nodosum) and some growth regulators (GA3 and NAA) to reduce fruit drop and improve fruit yield and quality of winter guava trees cv. ‘Maamoura’ grown in Rasheed area, El Beheira, governorate, Egypt and cultivated at a distance of 4 x 4 m. The irrigation method was flood irrigation from the Nile River. Trees, as uniform as possible in shape and size, were selected and had the same horticultural management including the control. The experiment involved ten foliage spraying treatments as follows: control, sprayed with water, Seaweed extract at (5, 10 and 15 mg/l), GA3 at (1, 2 and 3 mg/l) and NAA at (1, 2 and 3 mg/l). The obtained results showed that, GA3 at 3mg/l and Seaweed extract at 15 mg/l had the highest positive effect to improve vegetative growth, total chlorophyll (SPAD), the percentages of fruit set, yield, and total soluble solids (TSS). Moreover, it increased N, P and K in the leaves in the two seasons, as compared to the control and the other treatments. In addition, it improved significantly the number of fruits per tree, fruit weight, length and firmness. Reduction in the percentages of total acidity was observed as compared to the control, in the two seasons.
Guava (Psidium guajava L.) which belongs to family Myrtaceae is a native of tropical America. The fruit is rich in Vitamin-C and pectin besides being a good source of thiamine and riboflavin. It is known as ‘apple of tropics’ and can be grown in wide range of soil and climatic conditions. Guava is important fruit crop which is grown commercially in tropical and subtropical regions of the world (Gollagiet al., 2019).
Seaweeds or algae extracts include green, brown and red marine macro-algae, and brown seaweed extracts are widely used in horticulture crops. The raw material, geographical location of harvested algae and algal species, as well as the extraction method, all influence the composition of seaweed extracts, Polysaccharides, proteins, polyunsaturated fatty acids, pigments, polyphenols, minerals, plant growth hormones, and other physiologically active chemicals are transported from algal biomass to the liquid phase. They benefit humans, animals, and plants by primarily protecting an organism from biotic and abiotic stress and have various commercially valuable products such as pharmaceutical and cosmeceutical compounds (Al- Musawi, 2019)
Plant growth regulator like GA3 and NAA affects flower and fruit setting, cell growth, apical dominance, geotropism and photoperiod. GA3 had the highest fruit retention and yield followed by amcotone, activated dry yeast and NAA in both winter and rainy seasons. The growth regulators spray in addition increases fruit weight, total soluble solids (TSS), fruit weight, carotene, reducing sugars, total sugars and vitamin-C and decreased tannin and fruit acidity. The Triacontanol is present as a natural component of plant wax and bee wax (Abubakar et al., 2013).
GA3 is responsible for cell elongation, rather than cell division (Francis and Sorrell 2001). Gibberellins are natural growth hormones playing a primary role in stimulating the auxin reaction, which helps controlling the growth, as well as its direct effect on internode elongation, flowering, fruiting, quality and yield. The most typical property of gibberellins is the promotion of stem growth (Graebe, 1987). GA3 encourages the cell division and elongation; increases the stalk length, enhances flower and fruit volume. Auxins promote shoot elongation, thin tree fruit and flower formation (Fishel, 2006).
Naphthaleneacetic acid ( NAA) is an organic compound, which is a plant hormone in the auxin family and is an ingredient in many commercial horticultural products; it is also a rooting agent and used for the vegetative propagation of plants from stem and leaf cutting (Dimitrios et al., 2008).It has important role in fruit formation, abscission cell elongation, apical dominance, photoperiod and geotropism (Haidry et al., 1997).
The purpose of this study was to investigate the effect of foliar application of seaweeds, GA3 and NAA on vegetative growth, fruit set, yield, fruit quality and leaf mineral of 'Maamoura' guava trees.
MATERIALS AND METHODS
This study was conducted during 2018 and 2019 seasons to investigate the effect of foliar application of marine algae extracts (Ascophyllum nodosum), GA3 and NAA to reduce fruit drop and improve fruit yield, fruit quality and leaf mineral content of winter guava cv. ‘Maamoura’ trees grown in Rasheed area, El Beheira, governorate, Egypt and cultivated at a distance of 4 x 4 m. the irrigation method was flood irrigation from the Nile River. During the entire season, all trees under study received the same applied fertilization program in orchard i.e. 2-3 miqtaf decomposed livestock manure +1 kg super phosphate and incorporated well in the soil in winter. In March and July, 200 - 250 g nitrogen was added to each tree in two batches. Potassium fertilizer was also added in two batches, exchange with nitrogen, at the rate of 150 - 250 kg per acre. Microelements was added both as foliar application to the shoot system and as soil application when deficiency symptoms appear. The physio-chemical analysis of experimental soil is indicated in Table (1).
Table (1): The physical and chemical analysis of the experimental soil
Depth (cm)
Textural class
pH
Total CaCO3
(%)
EC (ds/m)
O.M. (%)
0-45
Yellow soil
8.00
5%
0.28
3.3
Cations (meq/ 100 g soil)
Anions (meq/ 100 g soil)
Na+
K+
Ca2+
Mg2+
HCO3-
Cl-
SO42-
5.6
0.33
0.45
0.55
1.4
2.8
2.8
The following treatments were sprayed on the trees:
Control (Tap water)
Seaweed extract at 5 mg/l. (Sea- Hammer)
Seaweed extract at 10 mg/l.
Seaweed extract at 15 mg/l.
GA3 at 1 mg/l.
GA3 at 2 mg/l.
GA3 at 3 mg/l.
NAA at 1 mg/l.
NAA at 2 mg/l.
NAA at 3 mg/l.
The Sea Hammer compound was used as the source of the algae escophyllum nodosumsp. ( 85% alge extract ,10% humic acid and 5% potassium).
Gibberellic acid ( From Green Geb 10% GA3 tablets) and naphthalene acetic acid ( from Green hand tonic) (contains: 1.2% Sodium A Naphthyl acetic acid, 0.6% Sodium O- Nitrophenollate, 0.9% Sodium P- Nitrophenolate and 0.15% Sodium 2,4- Dinitrophenolate).
They were sprayed three times:
one month before full flowering (25 May)
one month after fruit setting (10 July)
one month before harvest (20 August)
The previous treatments were arranged in Randomized Complete Block Design (RCBD), each treatment was replicated on 3 trees. The effect of the previous treatments was studied by evaluating their influence on the following parameters.
1.Vegetative Parameters
Samples of three trees of each experimental unite were taken to determine growth parameters at the middle of each season as follows.
1.1 Shoot length (cm)
1.2 Shoot diameter (mm)
1.3 Total chlorophyll in the fresh leaves was determined as SPAD units by using Minolta chlorophyll meter (SPAD, 501).
2.Fruit set (%), yield (kg/tree) and yield components
2.1 Fruit set (%)
Twenty branches from each of the eight treatments were chosen at random to evaluate the percentage of fruit set; they were then tagged, and their blooms were counted when they were in full bloom. Fruitlets were also counted and recorded in mid-June, as fruit set was ideal. As a percentage of the total number of blooms, fruit set was estimated as follows:
Fruit set (%) =
2.2 Yield (kg/tree)
At harvest time, in 10th, October in the two seasons, the yield of each treatment was measured in kilogrammes per tree. (mature fruits were picked, counted and weighed in Kg per tree).
Sample of 10 fruits per tree from each replicate was collected randomly, i. e. 50 fruits from each applied Samples were taken at random at harvest in both seasons and brought to the laboratory quickly to determine physical and chemical fruit characteristics.
2.3 Yield components
2.3.1 Physical fruit characteristics
The following parameters were determined:
2.3.1.1 Fruit weight (g/ fruit)
Fruit samples were weighted and the average fruit weight for each replicate was calculated in gram.
2.3.1.2 Fruit length (cm) and diameter (cm): were measured by using Hand caliper.
2.3.1.3 Fruit firmness (pound/ Inch2): Flesh firmness was measured in two opposite sides of the fruit using magness taylor pressure tester and expressed as (pound/ Inch2) according to (Magness and Taylor, 1982).
2.3.2 Chemical fruit characteristics
2.3.2.1 Total soluble solids ( TSS %)
The percentage of TSS was determined in guava fruit juice using a hand refractometer according to (A.O.A.C, 1995).
2.3.2.2 Total acidity (%)
The percentage of total acidity in fruit juice was calculated using Chen and Mellenthin (1981) method. Five milliliters from the obtained juice were used to determine the titratable acidity. The titratable acidity was expressed as grams citric acid/ 100 milliliters fruit juice.
2.3.2.3 Vitamin C (Ascorbic acid) ( mg/ 100g pulp)
The ascorbic acid content of the juice was determined by titration with 2, 6 dichloro phenol-indo-phenol (A.O.A.C., 1995) and calculated as milli-grams per 100 ml of juice.
2.3.2.4 Total sugars (%)
Total sugar (%) was determined calorimetrically using phenol and sulphuric acid, according to Malik and Singh (1980) extracted from 5-gram fresh pulp.
3.Leaf mineral compositions (N,P and K)
Samples of the third pairs of leaves from the base of none fruiting shoots were collected in mid -August in both seasons of the study. At random from the previously tagged shoots, samples of 40 leaves /tree were taken, The leaf samples were washed in tap and distilled water before being oven dried at 70°C to a consistent weight and crushed. To assess the leaf mineral content, each sample's ground material was digested with H2SO4 and H2O2 according to the manufacturer's instructions Wolf (1982). Total nitrogen and phosphorus in the digested material were measured colorimetrically according to Evenhuis and De waard (1980) and Murphy and Riley (1962), respectively and potassium was determined using a flame photometer, as stated by Chapman and Pratt (1978). The concentrations of N, P and K were expressed as percent.
4.Statistical analysis
The results of the measured parameters were subjected to a computerised statistical analysis of variance (ANOVA) using the MSTAT programme, and the means of treatments were compared using LSD at 0.05 according to Snedecor and Cochran (1990).
The purpose of this research was to see how foliar spraying of seaweed extract, GA3, and NAA on guava cv. "Maamoura" trees improved fruit set %, vegetative development, yield, fruit quality, and leaf mineral content.
RESULTS AND DISCUSSION
Effect of seaweed extract, GA3 and NAA growth regulators on vegetative growth properties
The results regarding the shoot length (cm) and diameter (mm) and total chlorophyll (SPAD) of guava cv. "Maamoura" as influenced by seaweed extract, GA3 and NAA levels, during 2018 and 2019 are presented in Table (2).
As for seaweed, in the two seasons, the three concentrations of seaweed significantly increased the shoot length (cm), shoot diameter (mm) and the leaf total chlorophyll (SPAD) of guava cv. Maamoura compared to the control. In the meantime, increasing seaweed extract concentration significantly increased the shoot length, shoot diameter and the leaf total chlorophyll of guava cv. "Maamoura".
As for GA3, in the two seasons, the three concentrations of GA3 significantly increased the shoot length (cm), shoot diameter (mm) compared to the control. In the meantime, there were significant differences among the three GA3 concentrations so that the shoot length and shoot diameter increased by increasing the concentrations of the GA3. in the two seasons, the two higher (2mg/l and 3mg/l) concentrations of GA3 significantly increased the leaf total chlorophyll of guava cultivar Maamoura compared to the control and the lowest concentration of GA3(1mg/l) treatment. While, the lowest concentration of GA3 (1mg/l) caused a significant decrease in the leaf total chlorophyll of guava cultivar Maamoura compared to the control in the two seasons.
As for NAA, in the two seasons, the two higher concentrations of NAA (2mg/l and 3mg/l) significantly increased the shoot length (cm) and shoot diameter (mm) compared to the control treatment. The highest concentration of NAA(3mg/l) caused a significant increase in leaf total chlorophyll (SPAD) of guava cultivar Maamoura compared to the control and the two lower concentrations (1mg/l and 2mg/l). In the meantime, the lowest concentration caused a significant decrease in the leaf total chlorophyll of guava cultivar Maamoura compared to the control and the other treatments, in the two seasons of the experiment.
It was clear that seasweed had a good influence on vegetative growth because of its high content of growth promoting hormones like IBA, cytokinins, IAA, gibberellins, and amino acids,vitamins, antibiotics and micronutrients (Zodape et al., 2008). Chlorophyll content was enhanced by seaweeds and seaweed products (Blunden et al., 1997), due to the reduction in chlorophyll degradation, which caused in part by betaines in the seaweed extract (Whapham et al., 1993). Because of increased photosynthetic rates or the most efficient use of photosynthetic yields, gibberellic acid GA3 has the ability to boost plant growth and improvement in a number of experimental settings(Hifny et al., 2017). There have been various investigations on the role of GAs in photosynthetic processes in this scenario. Davies (1987) NAA is the artificial version of auxins, as indicated. Which play an important part in vascular tissue, cell division, differentiation, apical dominance, leaf withering, and fruit abscission.
Table (2):Effect of seaweed extract, GA3 and NAA growth regulators on vegetative growth and total chlorophyll
Treatments
Shoot length (cm)
Shoot diameter (mm)
Total chlorophyll
(SPAD (μ Molm-2))
Seasons
2018
2019
2018
2019
2018
2019
Control
52.83g
59.17g
2.69g
3.01g
40.26e
45.09e
Seaweed 5 mg/l
62.29e
69.77e
2.92e
3.27e
42.14d
47.20d
Seaweed 10 mg/l
69.21c
77.51c
3.24c
3.63c
46.82b
52.44b
Seaweed 15 mg/l
76.90b
86.13b
3.67a
4.11a
52.02a
58.26a
GA3 1 mg/l
67.46cd
75.56cd
2.78f
3.12f
38.70f
43.34f
GA3 2 mg/l
74.95b
83.94b
3.09d
3.46d
43.00d
48.16d
GA3 3 mg/l
83.29a
93.28a
3.44b
3.85b
47.78b
53.51b
NAA 1 mg/l
51.90g
58.12g
2.60g
2.92g
36.23g
40.58g
NAA 2 mg/l
57.66f
64.58f
2.89e
3.24e
40.26e
45.09e
NAA 3 mg/l
64.07de
71.76de
3.21c
3.60c
44.73c
50.10c
Means with the same letters within each column are not significantly different at 0.05 level of significance
2. Effect of seaweed extract, GA3 and NAA growth regulators on fruit set and yield components
Results regarding fruit set (%), fruit weight (g), number of fruits/ tree and yield (kg/ tree) of guava cv. "Maamoura" as influenced by seaweed extract, GA3 and NAA levels are presented in Table (3).
Results presented in Table (3) indicated that, in the two seasons, the three concentrations of seaweed significantly increased fruit set (%), fruit weight (g), number of fruits/ tree and yield (kg/ tree) of winter guava cultivar Maamoura compared to the control treatment. In the meantime, there were significant differences among the three treatments so that fruit set (%) and fruit weight(g), number of fruits/ tree and yield (kg/ tree) increased by increasing the concentrations of seaweed extract.
As for GA3, in the two seasons, the three concentrations of GA3 significantly increased fruit set (%) and fruit weight(g), number of fruits/ tree
and yield (kg/ tree) of winter guava cultivar Maamoura compared to the control treatment, except for the lowest concentration (1 mg/l) for the number of fruits/ tree in the two season. In the meantime, there were significant differences among the three treatments, in the two seasons for the four measured traits.
As for NAA, in the two seasons, the three concentrations of NAA significantly increased fruit set (%) and fruit weight(g), number of fruits/ tree and yield (kg/ tree) of winter guava cv. Maamoura compared to the control treatment, except for the lowest concentration (1 mg/l) for the number of fruits/ tree in the two seasons and the lowest concentration for yield (kg/ tree) in the second season. In the meantime, there were significant differences among the three treatments for all traits, except between the two higher concentrations (2 and 3 mg/l) in the first season for the number of fruits/ tree.
The above results clear that, seaweed has a good influence on yield and fruit quality and this could be because of its high content of growth promoting hormones like IBA, IAA, cytokinins, gibberellins,vitamins, micronutrients, amino acids, and antibiotics (Zodape et al., 2008). Baghdady et al. (2014) sprayed In comparison to control plants, Valencia orange trees treated with GA3 at concentrations of 15 or 25 at full bloom stage had higher initial and ultimate fruit set percentages. Fruit weight increased by increasing the beneficial effect of GA3 from the mobilization of food reserves and accumulation of more pulp. This result is in conformity with that of Lal et al. (2013) on guava.
The exogenous supply of NAA treatment aided in the strengthening of the middle lamella and, as a result, the cell wall, and may have increased the mobilisation of food materials and minerals from other parts of the plant towards the development of highly active metabolic sink fruits, resulting in increased fruit weight. (Katiyar et al., 2009). These observations are also in line with what has been described by Anawal et al. (2015) in the pomegranate and Pandey et al. (2001) in guava. Vani et al. (2020), also found that, The use of GA3 and NAA enhanced cell proliferation and cell elongation, which resulted in larger fruits.
The rise in yield, which was accompanied by an increase in the quantity of fruits, a low percentage of fruit drop, higher fruit retention, and increased fruit size and weight under the growth regulators treatment, was verified by those previously reported by Jawed (2017).
Table (3):Effect of seaweed extract, GA3 and NAA growth regulators on fruit set and yield components
Treatments
Fruit set
(%)
Fruit weight
(g)
Number of
Fruit/ tree
Yield
(Kg/ tree)
Seasons
2018
2019
2018
2019
2018
2019
2018
2019
Control
56.62e
60.61e
142.32h
167.47h
83.11fg
104.28fg
11.82f
17.46f
Seaweed 5 mg/l
65.24f
73.07f
158.07f
196.22e
102.97de
115.32de
16.27d
22.62d
Seaweed 10 mg/l
72.50c
81.20c
176.74d
220.24c
114.41c
128.13c
20.22b
28.21b
Seaweed 15 mg/l
80.55a
90.22a
197.49b
246.93a
127.12a
142.37a
25.01a
34.93a
GA3 1 mg/l
61.57g
68.96g
167.40e
179.25f
95.69f
107.17f
16.01d
19.21e
GA3 2 mg/l
68.41d
76.62d
187.11c
201.39d
106.32d
119.08d
19.89c
23.98d
GA3 3 mg/l
76.01b
85.13b
209.11a
225.99b
118.13b
132.31b
24.70a
29.90b
NAA 1 mg/l
58.80h
65.86h
147.67g
172.78g
90.03g
100.84g
13.30e
17.42f
NAA 2 mg/l
65.34f
73.18f
165.19e
194.20e
100.04e
112.04e
16.53d
21.75e
NAA 3 mg/l
72.60c
81.31c
184.65c
218.00c
111.15e
124.49c
22.52b
27.13c
Means with the same letters within each column are not significantly different at 0.05 level of significance
3. Effect of seaweed extract, GA3 and NAA growth regulators on some fruit physical properties
The results regarding fruit length (cm), diameter (cm) and firmness (Ib/ inch2) of guava cv. "Maamoura" as influenced by seaweed extract, GA3 and NAA levels are presented in Table (4).
As for seaweed extract, results in Table (4) showed that, in the two seasons, the three concentrations of seaweed extract significantly increased fruit length (cm), fruit diameter (cm) and fruit firmness (Ib/ inch2) compared to the control treatment, except for the lowest concentration (5 mg/l) for fruit diameter (cm), in the two seasons. In the meantime, there were significant differences among the three concentration (5, 10 and 15 mg/l) for fruit length, diameter and firmness which increased by increasing the concentrations of the seaweed extract.
As for GA3, in the two seasons, the three concentrations of GA3 significantly increased fruit length (cm), fruit diameter (cm) and fruit firmness
(Ib/ inch2) compared to the control treatment. In the meantime, there were significant differences among the three GA3 concentrations for fruit length, diameter and firmness which increased by increasing the concentrations of GA3 during the two seasons.
As for NAA, in the two seasons, the two higher concentrations of NAA significantly increased fruit length (cm) and fruit firmness (Ib/ inch2) compared to the control and the lowest concentration of NAA. In the meantime, there were significant differences between the highest concentration (3 mg/l) compared to the middle one (2mg/l), during both seasons. While, the highest concentration of NAA (3 mg/l) caused a significant increase in fruit diameter compared to the control and the two lower concentrations (1 and 2 mg/l) in the first season and compared to the control and the lowest concentration (1 mg/l) in the second season.
Form the above results, seaweed has a good influence on yield and fruit quality and this could be because of its high content of growth promoting hormones like IAA, IBA, cytokinins, gibberellins, and amino acids, vitamins, antibiotics and micronutrients (Zodape et al., 2008). It is well known that, NAA and GA3 had many functions in plant nutrition and growth that influence physical properties of fruits. These included enhancing metabolic processes such as protein synthesis; cell division and fruit growth. The aforementioned roles of the two growth regulators could explain its effect on improving fruit physical properties and photosynthesis; activation of carbohydrate metabolized for synthesis of amino acids (Arunadevi et al., 2019 and Abd El-Sabor, 2020) on lime trees.
Table (4):Effect of seaweed extract, GA3 and NAA growth regulators on some fruit physical properties
Treatments
Fruit length
(cm)
Fruit diameter
(cm)
Fruit firmness
(Ib/ inch2)
Seasons
2018
2019
2018
2019
2018
2019
Control
6.30e
7.06e
5.91c
6.62c
4.95g
5.76g
Seaweed 5 mg/l
7.67c
8.59c
5.78cd
6.48cd
5.76e
5.85e
Seaweed 10 mg/l
8.52b
9.54b
6.42b
7.19b
6.40c
7.17c
Seaweed 15 mg/l
9.47a
10.60a
7.14a
7.99a
7.11a
7.96a
GA3 1 mg/l
7.16d
8.02d
5.46de
6.11de
5.47f
6.13f
GA3 2 mg/l
7.95c
8.90c
6.34b
7.10b
6.08d
6.80d
GA3 3 mg/l
8.83b
9.89b
7.04a
7.89a
6.75b
7.56b
NAA 1 mg/l
6.37e
7.14e
5.18e
5.81e
5.16g
5.78g
NAA 2 mg/l
7.8d
7.93d
5.76cd
6.45cd
5.74e
6.43e
NAA 3 mg/l
7.87c
8.81c
6.40b
7.17d
6.37c
7.14c
Means with the same letters within each column are not significantly different at 0.05 level of significance
4.Effect of seaweed extract, GA3 and NAA growth regulators on some fruit chemical characters
Results regarding the percentage of total soluble solids (TSS%), acidity (%), vitamin C (mg/ 100 ml) and total sugars (%) of guava cv. "Maamoura" as influenced by seaweed extract, GA3 and NAA levels are presented in Table (5).
As for seaweed, in the two seasons, the three concentrations of seaweed extract significantly increased the fruit total soluble solids (TSS), vitamin C (mg/ 100 ml juice) and total sugars (%) compared to the control treatment. In the meantime, there were significant differences among the three seaweed extract concentrations for fruit total soluble solids percentage, vitamin C (mg/ 100 ml juice) and total sugars (%) which increased by increasing the concentrations of the seaweed extract. In contrast, the three concentrations of seaweed extract significantly decreased fruit acidity percentage compared to the control treatment in the two seasons. In the meantime, there were significant differences among the three seaweed extract concentrations for fruit acidity which decreased by increasing the concentrations of the seaweed extract.
As for GA3, in the two seasons, the three concentrations of GA3 significantly increased fruit total soluble solids (TSS) percentage, vitamin C (mg/ 100 ml juice) and total sugars (%) compared to the control treatment. In the meantime, there were significant differences among the three GA3 concentrations for fruit total soluble solids percentage, vitamin C (mg/ 100 ml juice) and total sugars (%) which increased by increasing the concentrations of GA3 during both seasons. In contrast, the three concentrations of GA3 significantly decreased the fruit acidity percentage compared to the control treatment in the two seasons. In the meantime, there were significant differences among the three GA3 concentrations for fruit acidity which decreased by increasing the concentrations of GA3.
As for NAA, in the two seasons, the three concentrations of NAA significantly increased fruit total soluble solids (TSS) percentage, vitamin C (mg/ 100 ml juice) and total sugars (%) compared to the control treatment. In the meantime, there were significant differences among the three NAA concentrations for fruit total soluble solids percentage, vitamin C (mg/ 100 ml juice) and total sugars (%) which increased by increasing the concentrations of NAA during both seasons. In contrast, the three concentrations of NAA significantly decreased the fruit acidity percentage compared to the control treatment in the two seasons. In the meantime, there were significant differences among the three NAA concentrations for fruit acidity which decreased by increasing the concentrations of the NAA.
This considerable rise in TSS content of fruit could be explained by GA3 stimulating the operation of a number of enzymes in the physiological process, which likely caused the reported increase in TSS content of fruit by Garmendia et al. (2019). According to, the drop in acidity in growth regulators treated fruits could be related to the quick consumption of organic acid during respiration at maturity by Agnihotri et al (2013) and Rajput et al (2016).
The GA3 treatment raised the sugar content in the fruit by stimulating the production of the hydrolytic enzyme, which dissolved complex polysaccharides into simple sugar. Growth regulators promoted the transfer of photosynthetic metabolites from other areas of the plant to growing fruits. This discovery is consistent with the findings of Kumar and Rattanpal(2010) in guava. The proportion of total sugars could be ascribed to growth regulators' assist in photosynthesis, which resulted in further oligosaccharides and polysaccharides getting formed. They also control enzymatic activity, ensuring that enzymes swiftly convert starch to soluble sugars, resulting in early ripening in response to growth stimuli. Observations similar to these were made by Agnihotri et al (2013) in guava.
Table (5):Effect of seaweed extract, GA3 and NAA growth regulators on some fruit chemical characters
Treatments
TSS
(%)
Acidity
(%)
VC
(mg/100g)
Total sugars
(%)
Seasons
2018
2019
2018
2019
2018
2019
2018
2019
Control
8.37h
9.38h
0.54a
0.61a
167.39h
187.47h
5.64h
6.32h
Seaweed 5 mg/l
10.10e
11.31e
0.40d
0.45d
193.05e
216.22e
7.81c
8.74c
Seaweed 10 mg/l
11.22c
12.56c
0.36e
0.40e
214.50c
240.24c
8.67b
9.72b
Seaweed 15 mg/l
12.46a
13.96a
0.32f
0.36f
238.33a
266.93a
9.64a
10.79a
GA3 1 mg/l
9.41f
10.54f
0.44c
0.49
177.90f
199.25f
7.02e
7.87e
GA3 2 mg/l
10.46d
11.71d
0.40d
0.45d
197.67d
221.39d
7.81c
8.74c
GA3 3 mg/l
11.68b
13.08b
0.35e
0.39e
219.64b
245.99b
8.76b
9.80b
NAA 1 mg/l
9.07g
10.15g
0.49b
0.55b
172.12g
192.78g
6.06g
6.79g
NAA 2 mg/l
9.30f
10.42f
0.44c
0.50c
191.25e
214.20e
6.73f
7.54f
NAA 3 mg/l
10.33d
11.57d
0.40d
0.45d
212.50c
238.00c
7.48d
8.38d
Means with the same letters within each column are not significantly different at 0.05 level of significance
5. Effect of seaweed extract, GA3 and NAA growth regulators on some leaf macro nutrients
The results regarding the percentages of nitrogen, phosphorus and potassium contents of guava cv. "Maamoura" as influenced by seaweed extract, GA3 and NAA levels are presented in Table (6).
The data in Table (6) showed that, in the two seasons, the three concentrations of seaweed extract (5, 10 and 15 mg/l) significantly increased the leaf nitrogen, phosphorus and potassium percentages compared to the control treatment. In the meantime, there were significant differences among the three seaweed extract conentrations for nitrogen, phosphorus and potassium percentages content which increased by increasing the concentration of the seaweed extract.
As for GA3 in the two seasons, the three concentrations of GA3 (1, 2 and 3 mg/l) significantly increased the leaf nitrogen, phosphorus and potassium percentages compared to the control. In the meantime, there were significant differences among the three GA3 concentrations for nitrogen, phosphorus and potassium percentages content which increased by increasing the concentration of the GA3.
As for NAA, in the two seasons, the three concentrations of NAA (1, 2 and 3 mg/l) significantly increased the nitrogen, phosphorus and potassium percentages compared to the control treatment. In the meantime, there were significant differences among the three NAA concentrations for leaf nitrogen, phosphorus and potassium percentages which increased by increasing the concentrations of the NAA.
It was clear that, seaweed contains a high amount of potassium, nitrogen and phosphorous (Elumalai and Rengasamy, 2012). The content of macronutrients in the leaves of seaweed extract has been found to improve (Mancuso et al., 2006). In addition, the quantities of K, Fe, and Cu in the leaves of olive trees sprayed with marine extract increased (Chouliaras et al., 2009). A promoting of biomass has been shown to exert production of Gibberellic acid induces DNA, RNA, and protein synthesis along with ribose and polyribosome proliferation in vegetative organs. GA3 treated trees accumulate biomass Improvements in enzyme activity and membrane permeability may make mineral nutrient absorption and utilisation easier and transport of photosynthates (Miceli et al., 2019).
Table (6):Effect of seaweed extract, GA3 and NAA growth regulators on some leaf macro nutrients
Treatments
N
(%)
P
(%)
K
(%)
Seasons
2018
2019
2018
2019
2018
2019
Control
1.40j
1.57j
0.200h
0.224h
1.85h
2.07h
Seaweed 5 mg/l
1.92e
2.15e
0.347cd
0.388cd
2.65c
2.97c
Seaweed 10 mg/l
2.14c
2.39c
0.390b
0.437b
3.07b
3.44b
Seaweed 15 mg/l
2.37a
2.66a
0.430a
0.481a
3.28a
3.67a
GA3 1 mg/l
1.81g
2.03g
0.293b
0.329e
2.24fg
2.51fg
GA3 2 mg/l
2.01d
2.25d
0.327d
0.366d
2.49de
2.79de
GA3 3 mg/l
2.23b
2.50b
0.363c
0.407c
2.77c
3.10c
NAA 1 mg/l
1.52i
1.70i
0.227g
0.254g
2.13g
2.39g
NAA 2 mg/l
1.69h
1.89h
0.253f
0.284f
2.37ef
2.65ef
NAA 3 mg/l
1.87f
2.10f
0.283e
0.317e
2.63cd
2.94cd
Means with the same letters within each column are not significantly different at 0.05 level of significance
CONCLUSION
The foliar application of seaweed, GA3 and NAA had a positive effect in improving the vegetative growth, fruit set, yield, fruit quality and leaf mineral content, of 'Maamoura' winter guava trees. Seaweed 15 mg/, GA3 3 mg/l and NAA 3 mg/l was the best treatments. These treatments had the highest positive effect in improving the vegetative growth, percentages of yield, fruit set, fruit weight, number of fruits per tree, fruit length and width. It also, increased P content in the leaves in the two seasons, as compared to the control treatment. Moreover, it improved significantly fruit firmness. It decreased the percentages of acidity in the two seasons as compared to the control and the other treatments.
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