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Pak. J. Bot., 47(6): 2247-2255, 2015.

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Effect of regulated deficit irrigation on the morphology, physiology, carbon allocation and nonstructural carbohydrates of three Kentucky bluegrasses

Jin Rong Liu¹*, Xiao Rong Xie ², Li Ma¹, Yi Kai Liu ¹, tie jun liu¹, jian nan lu¹ AND dang ni wang¹

¹State Key Laboratory of Grassland Agro-ecosystems , College of Pastoral Agriculture, Science and Technology, Lanzhou University , Lanzhou 730020 , China

² Gansu College Tradition Chinese Medicine, Lanzhou 730020, China

*Corresponding author’s e-mail address: liujinr@lzu.edu.cn

Abstract: Regulated deficit irrigation (RDI) has been assessed in a wide number of field and fruit crops. However, few are the studies dealing with turfgrass. This study was conducted to investigate the morphology, physiology and carbon metabolic responses to regulated deficit irrigation for three Kentucky bluegrass (Poa pratensis L.) cultivars. Three Kentucky bluegrass cultivars were grown in PVC (polyvinyl chloride) tubes in a greenhouse and subjected to three soil water treatments in a growth chamber: 1) full irrigation; 2) drought stress, 21 days without water after full irrigation; and 3) drought recovery, stressed plants were re-watered for an additional 21 d. The present study indicated that drought resulted in a decline in turf quality (TQ), leaf relative water content (RWC), and photochemical efficiency (Fv/Fm) and an increase in electrolyte leakage (EL) for the cultivars. The turf quality, RWC, and Fv/Fm of the three Kentucky bluegrass cultivars increased with re-watering. The allocation of ¹⁴C increased in the roots of these cultivars during the initial phase of drought stress, where a ¹⁴C distribution shift from the roots to the stem and leaves appeared with further drought stress. Moreover, there was a significant accumulation of total nonstructural carbohydrates (TNC) in the leaves and stem. The TNC content in the leaves, stem, and roots did not completely return to the control levels following 21 d of re-watering, which was consistent with the recovery of TQ, RWC, Fv/Fm, and EL. In addition, during the re-watering treatment, the reduction in the TNC content may be due to increases in the demand or usage as a result of a rapid recovery in the growth and physiological activities as shown by increased TQ, RWC, and Fv/Fm and decreased EL. Our results suggested that the changes in the carbon allocation model and the accumulation and storage of TNC, as well as the changes in TQ, RWC, Fv/Fm, and EL, for the three cultivars are an adaptive reaction to drought and re-watering following drought. The accumulation and storage of TNC in plants during severe drought may contribute to the survival of meristematic regions and/or serve as reserves, which contribute to plant re-growth once the drought stress is alleviated. This result suggests that the allocation of carbon assimilates and their accumulation in different organs of turfgrass were a physiological adaptation response to drought and re-watering treatments, thus providing a scientific basis for further investigating the resistance of turfgrass to other adverse environments.

Key words: Drought, Recovery, Nonstructural carbohydrates, ¹⁴C allocation.