Chin J Plan Ecolo ›› 2018, Vol. 42 ›› Issue (6): 681-691.DOI: 10.17521/cjpe.2018.0017

• Research Articles • Previous Articles     Next Articles

Physiological and ecological responses to drought and heat stresses in Osmanthus fragrans ‘Boyejingui’

WANG Jun-Yu,WANG Xiao-Dong,MA Yuan-Dan,FU Lu-Cheng,ZHOU Huan-Huan,WANG Bin,ZHANG Ru-Min,GAO Yan()   

  1. The State Key Laboratory of Subtropical Silviculture, Zhejiang Agriculture and Forestry University, Lin’an, Zhejiang 311300, China
  • Received:2018-01-14 Revised:2018-05-12 Online:2018-06-20 Published:2018-06-20
  • Contact: Yan GAO
  • Supported by:
    Supported by the National Natural Science Foundation of China(31470704);Supported by the National Natural Science Foundation of China(31270756)

Abstract:

Aims Drought and heat stresses are two critical environmental factors affecting the growth and development of plants; climate change has exacerbated the occurrence of these conditions in many parts of the world. To elucidate the mechanisms of responses to drought and heat stresses in Osmanthus fragrans, we studied changes in nonstructural carbohydrate (NSC) and volatile organic compounds (VOCs) emissions using 3-year-old seedlings (cultivar ‘Boyejingui’) under conditions of low drought (LD), moderate drought (MD) and severe drought (SD), interactively with heat treatments (40 °C in daytime (12 h) and 30 °C at night (12 h)).

Methods The VOCs emissions were measured using the dynamic headspace air-circulation method, and the composition and content of VOCs were analyzed using the thermal desorption system/gas chromatography/mass spectrometer technique (TDS-GC-MS). We determined the content of NSC and activities of lipoxygenase (LOX), 3-hydroxy-3-methylglutaryl-CoA reductase (HMGR) and 1-deoxy-D-xylulose 5-phosphate reductoisomerase (DXR) in seedlings under different drought and heat treatments.

Important findings The content of NSC in leaves was not significantly affected by drought stress. The contents of soluble sugar and starch were significantly reduced by heat stress as well as combination of drought and heat stresses. The combination of severe drought and heat treatment significantly reduced the contents of glucose, fructose, sucrose and starch by 47.7%, 46.4%, 34.4% and 38.2% (p < 0.05), respectively. There were differences among the activities of HMGR, DXR and LOX in response to drought and heat stresses. Under drought and combined stresses, the activities of HMGR and DXR increased first and then decreased, and the LOX activity increased. The activities of HMGR, DXR and LOX were significantly higher under heat stress than in controls. The release of terpenes increased first and then decreased with the level of drought treatments. MD and SD stress stimulated the release of terpenes by 37.9% and 32.3% (p < 0.05), respectively, but the combined stresses induced a reduction in the release of terpenes. The release of aldehydes increased significantly in response to drought, heat treatment, and their combination. The results indicated that ‘Boyejingui’ seedlings can enhance resistance to drought stress by adjusting contents of non-structural carbohydrate and releasing terpene compounds. They also adjusted the biosynthesis of terpene compounds and GLVs emission to resist against heat stress. However, the biosynthesis pathway of terpene compounds was blocked in the occurrence of both drought and heat stresses, when the enhanced release of GLVs facilitated the resistance. Under heat stress, moderate and severe drought caused severe damage to cell membranes, thus reducing the self-regulatory capacity.

Key words: Osmanthus fragrans, drought and heat stress, non-structural carbohydrate, volatile organic compounds, secondary metabolic enzymes