پديد آورندگان :
عباسيان، عباس دانشگاه فردوسي مشهد - دانشكده كشاورزي - گروه زراعت , اسدي، قربانعلي دانشگاه فردوسي مشهد - دانشكده كشاورزي - گروه زراعت , قرباني، رضا دانشگاه فردوسي مشهد - دانشكده كشاورزي - گروه زراعت
چكيده لاتين :
Introduction: Invasive species are major cause of global environmental change and the second major threat
to biodiversity in the world after the destruction of ecosystems. Invasive plants change the plant species,
structure and function of the ecosystem and influence the abundance and diversity of native vegetation.
Centaurea balsam ita is a one-year-old plant of sunflower family that invades the fallow and slope lands. This
plant is reproduced by seed and distributed in Syria, Turkey, Iran, Afghanistan and Central Asia (Turkmenistan
to Tian Shan). Considering that the precise identification of problematic invasive species and gaining awareness
of their cold tolerance may provide access to basic information for management of such invasive plants. This
study was performed to evaluate the tolerance of coldacclimated invasive plant of Centaurea balsamita in fall
conditions toward freezing stress.
Materials and Methods: The experiments were conducted at Research Laboratory of Ferdowsi University
of Mashhad, Faculty of Agriculture, in 2014 in a completely randomized design with 5 replications. After cold
acclimation in the fall, seedlings of Centaurea balsarnita were exposed to seven freezing temperatures (0, -3, -6,
-9, -12, -15 and -18 °C) using thermogradient freezer. Freezer temperature was 5 oc at the beginning of the
experiment and after placing the samples inside, the temperature decreased with the speed of 3 oc per hour.
INBA (Ice Nucleation Active Bacteria) was sprayed on the samples at 3 °C. Plants were kept at each treatment
temperature for two hours and then harvested, and then, pots were transferred to the cold chamber at 4 ± 2 oc
and kept for 12 to 24 hours there. The cytoplasm membrane stability of Centaurea balsamita was evaluated
using electrolyte leakage; then the lethal temperature of 50% of pots was determined based on leakage
percentage (L Tso,,). Survival percentage was measured by counting the number of live plants in each pot. Then,
at the end of the recovery period, the lethal temperature for 50% of survival percentage (LT,.,m) and reduction
temperature for 50% of dry weight (RDMTso) was determined (three weeks after the application of freezing
treatment). Data statistical analysis was performed using the MSTATC software. For diagramming and
determining the LTso'", the Excel and Sigmaplot software were used.
Results and Discussion: The lowest (6.9 percent) and the highest (82.7 percent) electrolyte leakage, were
observed at 0 oc and -18 °C, respectively. Temperature reduction from -12 oc to -15 oc caused a significant
increase (P :S 0.05) in electrolyte leakage in Centaurea balsamita. In cold acclimated Centaurea balsam ita, with
fall conditions, the highest survival percentage was observed at 0 °C, -3 oc and -6 °C, and the lowest at -15 °C
and -18 °C. Also, temperature reduction from -9 octo -12 oc caused significant decrease (P :S 0.05) in survival
percentage in Centaurea balsamita. The highest biomass dry weight of Centaurea balsamita after the recovery
period (21 days after application offreezing treatment) was observed at 0 oc and -3 °C, and the lowest at -15 °C
and -18 oc_ Temperature reduction from -9 oc to -I 2 oc caused a significant decrease (P :S 0.05) in biomass of
Centaurea balsamita. The results showed that LTsod, LTso'" and RDMTso of cold-acclimated Centaurea
balsamita in fall conditions were -I 3.2 °C, -I 26 oc and -I 1.8 °C, respectively.
Conclusions: This study showed that in invasive plants such as Centaurea balsamita, using electrolyte
leakage and survival tests can be relatively good methods in assessing and identifying invasive plants tolerant to
cold, and help to identify invasive plant cold tolerance, predict their distribution and invasion. Due to the fact
that L Ts0e1, LTso'". and RDMTso of cold-acclimated Centaurea balsamita with winter conditions in the present
are determined -13.2 °C, -12.6 oc and -11.8 °C, respectively, it can be stated that this plant is of the cold tolerant
plants and it is predictable that the spread and stabilization of this invasive plant is possible in cold regions. But
to ensure more about the cold tolerance of this invasive plant, it is recommended to cold acclimate this plant in
areas with higher elevation and colder than Mashhad to achieve more accurate assessment of cold tolerance. Due
to low L Tso"' of this plant when its seeds distributed, migration this invasive plant to wheat, barley and
rangelands is highly possible.
