ABSTRACT
Effects of foliar application of 100 mmol/L glycinebetaine (GB) on PS II photochemistry in wheat (Triticum aestivum) flag leaves under drought stress combined with high irradiance were investigated. The results show that GB-treated plants maintained a higher net photosynthetic rate during drought stress than non-GB treated plants. Exogenous GB can preserve the photochemical activity of PSII, for GB-treated plants maintain higher maximal photochemistry efficiency of PSII (F(v)/F(m)) and recover more rapidly from photoinhibition. In addition, GB-treated plants can maintain higher anti-oxidative enzyme activities and suffer less oxidative stress. Our data suggest that GB may protect the PSII complex from damage through accelerating D1 protein turnover and maintaining anti-oxidative enzyme activities at higher level to alleviate photodamage. Diethyldithiocarbamate as well as streptomycin treatment can impair the protective effect of GB on PSII. In summary, GB can enhance the photoinhibition tolerance of PSII.
Subject(s)
Betaine/pharmacology , Photosynthesis/drug effects , Triticum/drug effects , Water/physiology , Antioxidants/metabolism , Betaine/metabolism , Carbon Dioxide/metabolism , Chlorophyll/metabolism , Photosynthesis/physiology , Photosystem II Protein Complex/antagonists & inhibitors , Photosystem II Protein Complex/metabolism , Superoxide Dismutase/antagonists & inhibitors , Superoxide Dismutase/metabolism , Triticum/physiology , Triticum/radiation effectsABSTRACT
Two wheat cultivars (Triticum aestivum L.), HF9703 tolerant to drought and SN215953 sensitive to drought, were used to study the effects of glycinebetaine on the composition and function of thylakoid membrane. The wheat seedlings with two leaves were pretreated with Hoagland solution containing 1.5 mmol/L glycinebetaine (GB) for 72 h, then cultured with Hoagland solution containing 15% PEG-6000 for 48 h. The seedling leaves were used for mensuration. The results indicated that the chlorophyll, monogalactosyl diaylglycerol (MGDG), digalactosyl diacylglycerol (DGDG) and phosphatidylglycerol (PG) contents of the two wheat cultivars decreased significantly (P<0.05) under drought stress. GB alleviated their decrease. The sulfoquinovosyl diacylglycerol (SQDG) content, trans-hexadecenoic [16:1(3t)] and saturated fatty acid content of MGDG in HF9703 increased significantly (P<0.05), while in SN215953, the sulfoquinovosyl diacylglycerol (SQDG) and trans-hexadecenoic [16:1(3t)] contents decreased significantly under drought stress, but the saturated fatty acid content of MGDG increased slightly. These differences between the two wheat cultivars might account for much of the difference in drought tolerance between them. Ca2+-ATPase activity of thylakoid membrane, Hill-reaction activity and photosynthesis were decreased markedly (P<0.05) by drought stress. GB ameliorated these effects on thylakoid membrane, and the effect of GB on SN215953 was stronger than on HF9703. Discussion was made on the possible mechanism of the alleviating effect of root-applied GB on the composition and function of thylakoid membrane.
