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.
