Pomology
Fatemeh Karamnezhad; Norollah Moallemi; Esmaeil Khaleghi
Abstract
Introduction
Nitrogen plays an important role in the uniformity and quality of citrus trees. Several studies previously reported that a low level of nitrogen in citrus trees is generally caused a reduction in yield and fruit quality (Aziz, 1997; Khan et al., 2009). In this regard, applying urea is recommended ...
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Introduction
Nitrogen plays an important role in the uniformity and quality of citrus trees. Several studies previously reported that a low level of nitrogen in citrus trees is generally caused a reduction in yield and fruit quality (Aziz, 1997; Khan et al., 2009). In this regard, applying urea is recommended as the most suitable form of nitrogen for foliar application. The polyamines are included; putrescine, spermidine, and spermine which have been considered as plant growth regulators (Alcazar et al., 2010; Khezri et al., 2010). The role of nitrogen in vegetative and reproductive growth and yield, as well as the correlation between polyamines, flower induction and fruit set in other plants, were proved in previous studies. In this regard, the results of the current study will increase our understanding about the role of polyamines in the morphology of the tree and also the mechanism of regulating the alternate bearing of Kinnow mandarin leading to an approach method to address this problem.
Materials and Methods
To conduct this study a 17-year-old uniform of Kinnow Mandarin (Citrus reticulate Blanco) grafted onto Bitter orange (Citrus aurantium) rootstock, which grown in a commercial orchard, located in Dezful (Khuzestan Province in Iran). For sampling, the branches which possess leaves and nodes were selected from four sides of each tree, then leaves and nodes were collected at three different time points (one, three, and five weeks post-treatment). Samples were immediately frozen in liquid nitrogen after excision and transported to the Physiology Laboratory of fruit trees within 2h for determining the N fractions and polyamines. The concentration of N in dried leaves and nodes was determined using the colorimetry technique as described by Walling et al. (1989). The experiment was set up as a factorial treatment based on a randomized complete block design with three replications to investigate the effect of different concentrations of urea foliar application (0, 0.75%, 1.5%) on nitrogen and polyamines contents at different time points (Dec 22, Jan 5, Jan 20) followed by evaluating flower characteristics and yield in Kinnow mandarin plant. Data analysis including variance was carried out using MSTATC and SAS software. To compare the mean of polyamines and nitrogen in leaves and nodes, the cut-out method was used, and also for comparison of pistil dimensions, number of flowers, and yields, Duncan's multiple range test (DMRT) was performed.
Results and Discussion
Results indicated that polyamines concentration and nitrogen decreased during the period of time and also, in most cases, polyamines concentration was lower in the nodes than the leaves. High levels of polyamines and nitrogen were obtained in leaves and nodes which were treated with the foliar application of 1.5 % urea concentration after Jan 20. The polyamines content in leaves and nodes was greatly dependent on the spraying time and urea concentration used. Spermine (Spm) was the dominant polyamines in leaves and nodes with the highest values of 44.01 nmol/gF.W, 34.41 nmol/gF.W, respectively. Regarding the fact that flower density was higher in trees that treated with urea concentration of 1.5 % after Jan 5 y than other treatments, however, their yield was lower than the trees that treated on Dec 22 with the same urea concentration. This was probably due to the flower abscission as well as the fruit abscission in June. The results of this study showed that the highest yield was obtained with 1.5 % urea concentration after foliar application on Dec 22 compared with other treatments. Regarding the fact that flower differentiation in mandarin occurs during the late January until late February (in Dezful conditions), it can be explained that the foliar application on Dec 22 was performed before differentiation and consequently, the trees have received their required nitrogen. Also, the low-temperature is considered as natural inducer of citrus flowering in the Dezful, likewise, foliar fertilizer application in winter along with the natural factor (low temperature) stimulates flowering in a larger number of buds resulting in increasing the flowering. As nitrogen promotes vegetative and reproductive growth, it can be said that increasing the nitrogen content of leaves followed by transfering to the nodes, increases the number of buds, especially reproductive buds, which leads to an increase in flowering and yield. According to this study, the foliar application of urea in winter with 1.5% concentration can increase yield in Kinnow mandarin trees. Therefore, polyamines can play an important physiological role in flower development of Kinnow mandarin.
Conclusion
In this study, we focused on the effect of the foliar application urea during winter on leaves and nodes of Kinnow mandarin trees and investigated the polyamines, Put, Spm, and Spd contents upon treatments. In conclusion, the application of foliar urea in winter resulted in the significant endogenous increase of polyamines and N in the leaves and nodes of Kinnow mandarin trees. Also, yield, flower density, and pistil diameter were increased by spraying urea. There is a possibility that free polyamines affect on physiological processes.
Gholamhossein Davarynejad; Mina Nurzadehnamaghi; Ali Momen
Abstract
Introduction: Pistachio (Pistacia vera L.) is an important horticultural crop that has high economic value. Pistachio trees display some physiological disorders including abscission of inflorescence buds, fruit abscission, blankness, non-splitting, early splitting and deformation of nuts. Unfavorable ...
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Introduction: Pistachio (Pistacia vera L.) is an important horticultural crop that has high economic value. Pistachio trees display some physiological disorders including abscission of inflorescence buds, fruit abscission, blankness, non-splitting, early splitting and deformation of nuts. Unfavorable environmental conditions in most pistachio orchards and inadequate nutrition during the flowering time and after flowering has increased these problems in recent years. Polyamines such as putrescine, spermine and spermidine are some low molecular weight polycationic compounds that have been shown to play an important role as growth regulators in different stages of growth and development of buds, flowers and fruits and resistant plants to abiotic and biotic stress. Therefore, the objective of this study was to investigate the influence of polyamines in water scarcity condition on growth, nut traits and yield of ‘Akbari’ pistachio trees. Materials and Methods: The study was carried out in growing season 2016 in a pistachio orchard (Pistacia vera L. cv Akbari) located in Feyzabad, Mahvelat, Khorasan Province, Iran (34° 40´ N latitude, 58° 25´ E longitude, and around 1253 m above sea level). The climate of the experimental area was arid and semi-arid. The mean annual precipitation was about 171 mm. The irrigation of orchard trees was at 36-day intervals. The experiment was conducted as split plot based on a randomized complete block design with three replications and seven treatments including polyamines spray of Putrescine (Put), Spermine (Spm) and Spermidine (Spd) at concentrations of zero (control), 0.1 and 1 mM on “on” and “off” pistachio trees cultivar Akbari at two-time stages full bloom (FB) and two weeks after full bloom (2WAFB). Leaf chlorophyll index was recorded using the chlorophyll meter (SPAD-502, Konica Minolta, Japan). Leaf area from fully expanded leaves was measured by Digital Leaf Area Meter (LI-3100c). The length and diameter of current-year shoots were measured at harvest time. The percentage of flower bud abscission and fruit abscission were calculated on marked shoots. The yield was calculated by weighting the total dried split nuts separated from each shoot. The data were subjected to analysis of variances (ANOVA) using the SAS software (SAS version 9.1). Difference between means was compared using the least significant difference test (LSD) at 5% level (p ≤ 0.05). Results and Discussion: Results showed that among the treatments, Put (0.1 and 1 mM) and Spm (0.1 mM) applied in the “on” trees significantly increased leaf chlorophyll index. Also, Put spray at two weeks after full bloom indicated better results in increase of length shoot in ‘on’ trees. All of the polyamines reduced fruit abscission in the “on” trees however, Put at 0.1 and 1 mM concentrations with 11.3 and 11.1% was more effective in decreasing the percentage of fruit abscission compared to other treatments. Fruit abscission of pistachio is assumed to be related to improper fertilization, the dominance of fruits in a cluster or abnormalities of reproductive organs. Polyamines have been suggested to improve fertilization, and subsequent embryo and fruit development. It also has been reported that common precursor of S-adenosylmethionine (SAM) needed for synthesizing both of PAs and ethylene. Thus, it seems that polyamines reduce the abscission of fruits by the improvement of embryo growth and development or by antagonism with ethylene, possibly by competing for S-adenosylmethionine (SAM). Our study indicated that all of the polyamines decreased the percentage of blank nuts in the “off” trees especially two weeks after full bloom. The results showed that Put (0.1 and 1 mM) and Spd (0.1 mM) were very effective in increasing number of nuts per cluster. Number of nuts per 100 g, split nuts, and kernel percentage did not differ significantly among treatments. Yield variations were not significantly affected by polyamines in in the “off” trees, but in ‘on’ trees, polyamines of Put, Spm and Spd at 0.1 mM concentration by 46.2, 14.6 and 15.2% and at 1 mM concentration by 38.7, 24.7 and 19.9% increased yield compared to control, respectively. Given to correlation results, the positive effect of polyamines on yield improvement in ‘on’ trees was mainly due to the prevention from fruit abscission and enhancement no. of nuts per cluster. Conclusion: Results showed that application of polyamines treatments in ‘off’ trees only on blank nuts and in ‘on’ trees on leaf chlorophyll index, fruit abscission, No. of nuts per cluster and yield was effected. Foliar application of polyamines was more effective in improving traits of shoot length, leaf area and blank nuts two weeks after full bloom compared to full bloom. The results of this study showed that these plant growth regulators, especially putrescine, had the potential to improve growth, yield and reduce physiological problems of pistachio under unfavorable environmental conditions.
Hamid Mohammadi; Gholamhossein Davarynejad; Masud Khezri
Abstract
Introduction: Pistachio is one of the most important horticultural crops in Iran, USA, Turkey and some Mediterranean countries. Some physiological problems such as abscission of inflorescence buds, blankness, non-splitting, early splitting, cracking and nut deformation reduce the pistachio yield and ...
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Introduction: Pistachio is one of the most important horticultural crops in Iran, USA, Turkey and some Mediterranean countries. Some physiological problems such as abscission of inflorescence buds, blankness, non-splitting, early splitting, cracking and nut deformation reduce the pistachio yield and quality. A proper nutrition management of pistachio orchard might decrease the physiological problems and increasing the yield. Calcium is an essential plant macro-nutrient that has several distinct functions within plants. These functions can be divided into main areas including effects on membranes, enzymes, cell walls, and interactions of calcium with phytohormones. Free polyamines (putrescine, spermine, spermidine), are the widely distributed of N containing organic molecules binding to the intracellular anions (DNA, RNA, chromatin and proteins). They are also known to possess several regulatory functions. In plants, they have been associated with regulating many physiological processes, such as organogenesis, embryogenesis, floral initiation and development, leaf senescence, fruit development and ripening, and abiotic and biotic plant stress responses. Although the spray application of calcium compound and free polyamine has been investigated separately, application of calcium compounds combined with free polyamines has not been investigated yet. Therefore, the aim of this study was to evaluate the effect of combined treatments of calcium and free polyamines on decreasing the physiological problems and improving the yield of ‘Ahmad-Aghaii’ pistachio trees.
Materials and Methods: This experiment was carried out in a commercial 20-year old ‘Ahmad-Aghaii’ pistachio orchard in Rafsanjan, Iran. It was arranged as factorial based on randomized completely block design with three replications. The treatments were control, calcium compounds (calcium nitrate and calcium chloride at concentration of 0.5%) combined with free polyamines (putrescine, spermidine and spermine at concentration of 0.5 mM). Spraying were applied at different growth stages including two weeks after full bloom (stage 1), six weeks after full bloom (just before endocarp hardening) (stage 2) and the combination sprays of stage 1 and stage 2. Different traits including the percentages of abscission of inflorescence buds, cracking, blankness, early splitting, nut deformation, non-splitting and splitting as well as yield, leaf area and vegetative growth were measured. The individual shoot was the experimental unit and analyses of variance were performed using the General Linear Models procedure of SAS. Means were separated by Duncan’s multiple range test (P < 0.05).
Results and Discussion: Results showed that the main physiological problems of pistachio crop were decreased by application of calcium compounds combined with free polyamines. Spray application of the mentioned treatments was more effective at combined stages of 1 and 2 rather than the stages separately. It was resulted that calcium nitrate combined with spermine and spermidine treatments at combined stages of 1 and 2 reduced the abscission of inflorescence buds, blankness, nut deformation and non-splitting. Also, it was found that calcium nitrate combined with spermidine at combined stages of 1 and 2 reduced the percentage of early splitting while splitting and yield were increased. Spray application of free polyamines combined with calcium compounds did not affect the length and diameter of current-year shoots but significantly increased the leaf area. It seems that calcium plays a key role in conjunction with free polyamines especially spermidine and spermine in decreasing the abscission of inflorescence buds via improving the stability of cell wall and preventing abscission layer formation. It also seems that polyamines reduce the abscission of inflorescence buds by antagonism with ethylene, possibly by competing for S-adenosylmethionine (SAM), a common precursor of both plant bioregulators. Increasing the shoot yield and decreasing the percentage of blankness might be due to improving leaf photosynthesis as well as regulating kernel growth and development. It was found that free polyamines and calcium might promote a regulatory system against environmental stresses especially heat, drought and salinity which are the main concerns of pistachio growers.
Conclusion: According to the results, the application of calcium compounds combined with free polyamines could reduce the physiological problems and increased the yield of ‘Ahmad-Aghaii’ pistachio. Among calcium treatments, calcium nitrate was significantly more effective than calcium chloride. In the case of free polyamines, both spermidine and spermine were more effective than putrescine. It was concluded that application of calcium nitrate combined with spermidine or spermine at both stages (stage 1 + 2) was the most effective treatments in reducing physiological problems and increasing the yield of pistachio trees.
