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Abstract. One of the main problems in fruit production is the ambient low temperatures. It means that low temperature in early spring compromised the flowers and fruits. Apricot tree is known as an early blooming and sensitive to frost. In accordance to this in East Azarbaijan which is one of the important apricot production regions in Iran, rate of frost resistance of a few commercial apricot cultivars as Nassiri, Ghermez Shahrood, Dorosht Malaier, Ghorban Maraghe and Kanino were investigated. Experimental samples were studied under four different cold treatment levels (+2, 0, -2, -40C). Experimental traits include sensitivity and difference of anther, petal, stigma, style and ovary to temperature treatment, which have been morphologically evaluated. About all cultivars with progress of phenological stages and temperature decrease, damage percent increased. Among the above cultivars, Dorosh Malaier had a lowest and Ghorban Maraghe had a highest damage percent in low temperature. Nassiri, Ghermez Shahrood and Kanino were palced among mentioned cultivars. Proline quantity after cold treatment was evaluated as well. The results showed that between increase in proline and cold resistance in above mentioned cultivars don't have a complete liner correlation.
Key Words: Apricot, cold stress, phenological stages, proline.
Introduction. One of the most important fruit trees in Iran, especially in Azerbaijan region is the Apricot (Prunus armeniaca L.) whose products are used as fresh fruits, jam, can, etc. It's also exported to other countries. Apricot contains an important amount of K+, vitamin A, P, aspartic acid, glutamine and metionine (Tamassy & Zayan 1983).
In according to early flowering, cold stress injury is a limiting factor in planting and processing apricots, so in capable areas this factor cause production decreases. Chilling also decrease quality and quantity of products (Probesting 1978). This damage is mostly occurred thorough ice formation as long as cell survival depends on ice location. Ice formation may take place into or out cells (Hare & Cress 1997). A few factors are important in cold hardiness of flower buds, including genotype, flower phonological stages, ice formation place, water content and nutrition (Lu & Rieyer 1993; Rodrigo 2000). In late summer receptors in leaf get signals of shortening the days and produce substances in response which motivated cold hardening. These substances are transferred from leafy branches...