The Investigation of the Effects of Bulb Size on some Ornamental Traits and Flowering in some Tulipa Cultivars in the Climatic Condition of Mashhad

Tulip flower is one of the most popular flowers in the world. This bulbous flower has about 150 species with more than 6000 recorded cultivars. In the recent years, planting of ornamental bulbous plants such as tulip has been common in many cities of Iran during Nowruz. Selection and order of the bulbs often is done based on aesthetic and flowering factors. Feasibility of estimation of some aesthetic traits in tulip cultivars can be a management approach in the cities, so that if urban managers in the landscape field know the time and duration of flowering, they can have an exact plan for the tulip planting in the Nowruz. The study of ornamental traits, flowering date and duration of tulip flower have been studied in the different climatic and edaphic conditions. Tulip cultivars have prolong flowering periods that their flowering duration can match with Nowruz are an apocopate option to use in the urban landscape of Mashhad. One of the methods to estimate the vegetative and ornamental traits in the ornamental plants is prediction models using bulbous dimensions with other plant part dimensions or combinations of them. In the current paper the study of the date of flowering and its duration in the several cultivars was investigated. On the other hand an attempt has been made to establish a best method for estimation of some ornamental traits in the tulip flower.

In the first part of the examination, six plots including six cultivated cultivars of tulip with area of 5 m2 were prepared. Weight and diameter of bulbs were measured before planting and ornamental traits include height of flower stem, length and width of flower. Data from nearly 100 plants for each cultivar were recorded. Regression analyses of WB, DB, WB×DB, WB/DB, WB2×DB2 and WB2 /DB2 versus height of flower stem, length and width of flower were done. . Among tested models (linear, polynomial, power, logarithmic and exponential) the models with highest R2 values can be used for estimating of the mentioned ornamental traits. The correlation coefficients and also constants (a, b and c) were reported. In the other part of the examination, 23 cultivars of tulip in 15 plots with area of 20 m2 were planted in the various parts of Mashhad. Flowering date and also the duration of flowering from nearly 50 plants for each cultivar were recorded.

Results showed that the highest correlation between dimensions of bulbs (weight and diameter) with height of flower stem (R2=0.88) was observed in weight of bulbs. Among of the tested models , the highest coefficient of correlation was obtained in polynomial equation. The calculated correlation between weight and diameter of bulbs with length and width of flower were low. In the Royal virgin cultivar, flower length with the bulb weight and also multiple of the bulb weight and diameter significantly showed a positive correlation (R2=0.88 and R2=0.81). In the other part of the current study, results indicated that the most of studied cultivars showed different flowering dates and durations. According to the results, the most early-flowering cultivars obtained from Copex, Yokohama, Happy generation and Apricot beauty. The most lately-flowering cultivar of tulip in the present study was observed in Spring green.

In the first part of the study, the developed models including WB, WB×DB and WB2×DB2 that have the highest R2 levels in comparison with other models can be applied to estimate height of flower stem in most of tulip cultivars. In the second part of the study, among of the 23 cultivars, only Apricot fox, Pretty lady, Happy generation and Yokohama are advisable to plant in the urban landscape in Mashhad in order to have flower during the Nowruz.