نوع مقاله : مقاله پژوهشی
نویسندگان
1 گروه علوم باغبانی، دانشکده کشاورزی دانشگاه تهران، کرج، ایران.
2 گروه علوم باغبانی ، دانشکده کشاورزی دانشگاه تهران، کرج، ایران.
3 گروه علوم باغبانی، دانشکده کشاورزی دانشگاه تهران، کرج، ایران
4 گروه علوم باغبانی، دانشکده کشاورزی دانشگاه تهران. کرج. ایران
چکیده
کلیدواژه‌ها
موضوعات
عنوان مقاله [English]
نویسندگان [English]
Global warming is one of the major concerns of the current century. Net shading and foliar application of salicylic acid are options to protect plants against heat stress. This study investigated the protective effects of shading net and salicylic acid on vegetative growth, flowering and fruit attributes of apricot. Experimental treatments included net shading (green-50%) and salicylic acid (0.1 mM; three times foliar application), which were applied on trees of three apricot cultivars. The study was performed in the Horticultural Research Station of Horticultural Department, University of Tehran, Karaj, Iran in years 2019-2020. Shoot recurrent growth length, flower density, flowers, and fruits drop percentage, and fruit quality characteristics, as well as relative water content of leaf, cell membrane stability index, photosynthetic pigment, chlorophyll fluorescence were evaluated. Net shading could reduce leaf temperature by an average of 4.5 °C. It also increased the shoot recurrent growth length and flower density. The yield and quality of apricot fruits were affected by cultivar under the shade condition. The shading reduced evaporation and improved the water status (RWC) of apricot leaves and photosynthetic systems function. Since the net shading caused a delay on fruit ripening time and has negative effect on fruit coloring, the proper time for netting is near or after fruit harvesting especially in early ripening cultivars. Foliar application of salicylic acid in three intervals increased flower bud formation. Salicylic acid increased the leaf relative water content and photosynthetic system function. The results showed that salicylic acid made apricot trees more tolerant to heat stress. In general, application of green 50% net-shading after fruit harvesting is a chose of interest to improve flower formation and vegetative growth and SA application will reduce stress all the time of application during hot growth season.
کلیدواژه‌ها [English]
Extended Abstract
Introduction
Climate change and global warming are the major concerns of the current century. According to previous reports, the world is warming up about 0.2 °C per decade. This increasing in air temperature can cause heat stress in fruit trees in terms of heat stress injury in the summer and unsatisfying bud dormancy during the warm winter. Managing strategies for this tragedy include using protected cultivation such as net shading and foliar spraying of salicylic acid will be helpful to protect trees against summer heat stress.
Materials and Methods
Net shading and salicylic acid treatments were applied on trees of three apricot cultivars and performed as a Randomized Complete Block Design. Foliar application of salicylic acid in concentration of 0.00 (control) and 0.1 mM was applied three times with appropriate intervals on apricot trees. Some attributes related to vegetative growth and fruits such as recurrent shoot growth, flower density, flowers and fruit set percentage, fruit quality (TA, TSS, color, harvesting time), as well as the relative water content of the leaf, photosynthetic pigments and chlorophyll fluorescence were evaluated.
Results and Discussion
The time of ripening under shading net showed a 10 days delay with less colored fruits especially in late ripening cultivars. Net shading time depends on cultivars and is recommended when fruits were harvested or near to harvest stage. Applying green net (50%) on apricot trees reduced leaf temperature by an average of 4.5°C. Shading was able to increase current growth of branches and induction of flowers in the apricot trees. The yield and quality of apricot fruits were affected by cultivar under the net shading. The shading reduced evaporation and improved the water status of apricot tree leaves. This will help water relationship of trees under hot summer when water is not available sufficiently. It may also help to save water resources or running regulated deficit irrigation (RDI) system. Net shading also increased the membrane stability index and the photosynthetic systems function, which improves leaf gas exchange. This result showed that net shading was able to protect apricot trees against heat stress during the summer. Foliar application of salicylic acid in three consecutive times at a concentration of 0.1 mM on the apricot tree increased flower buds and next year's yield. Salicylic acid increased the relative leaf water content and photosynthetic system function.
Conclusion
In general, the results showed that net shading and salicylic acid made apricot trees more tolerant to summer heat stress. The time of applying net shading is important and cultivar-dependent. The main factor that requires consideration is fruit harvesting time. Early shading will reduce fruit color and other fruit quality attributes.
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