Taiwan J For Sci 27(3): 251-63, 2012 251 Research paper Response Variations of Alnus subcordata (L.), Populus deltoides (Bartr. ex Marsh.), and Taxodium distichum (L.) Seedlings to Flooding Stress Ehsán Ghanbary,1) Masoud Tabari,1,4) Francisco García-Sánchez,2) Mehrdad Zarafshar,1) Maria Cristina Sanches3) 【Summary】 Alnus subcordata is a native species distributed along bottomlands of Hyrcanian forests of northern Iran. In the last decade, this species along with the exotic species Populus deltoides and Taxodium distichum, has been widely used also for afforestation of bottomland areas. However, the relative flooding tolerance of these 3 species and their potential mechanisms for coping with flooding conditions are unknown to the present. Thus, in this study, variations in growth and mor- phophysiological responses to flooding of these species’ seedlings were investigated during a 120- d outdoor experiment. Seedlings were subjected to 3 fixed treatments of 1) unflooded, 2) flooded to 3 cm in depth, and 3) flooded to 15 cm in depth, and their survival, growth, and some metabolic parameters were measured at the end of the experiment. Survival in seedlings of these 3 species was very high, but the root length, biomass accumulation, and chlorophyll content were reduced by flooding. Diameter growth in T. distichum increased with flooding, while it was negatively affected in the other 2 species. The leaf area, specific leaf area, and height growth were reduced in A. sub- cordata and P. deltoides by flooding, while no significant effect on these parameters was observed in T. distichum. Flooding also induced the formation of hypertrophied lenticels, and adventitious roots in all 3 species. But, proline concentrations of roots and leaves of all species did not vary with flooding. Generally, our results clearly indicated that the 3 species assayed in this experiment could be used for afforestation of riparian and floodplain regions of Hyrcanian forests, since sur- vival percentages with 120 d of flooding were very high (> 90%). Key words: adventitious roots, afforestation, flood tolerance, leaf area, proline, survival. Ghanbary E, Tabari M, García-Sánchez F, Zarafshar M, Sanches MC. 2012. Response varia- tions of Alnus subcordata (L.), Populus deltoides (Bartr. ex Marsh.), and Taxodium disti- chum (L.) seedlings to flooding stress. Taiwan J For Sci 27(3):251-63. 1) Department of Forest Sciences, Tarbiat Modares Univ., Jalal Ale Ahmad Highway, PO Box 14115- 111, Tehran, Iran. 2 ) Instituto de Biologia, Campus Umuarama, Univ. Federal de Uberlândia, Caixa Postal 593, Uberlândia, MG 38400-902, Brazil. 3) CEBAS, CSIC, Campus Univ. de Espinardo, Espinardo 30100, Murcia, Spain. 4) Corresponding author, email:[email protected] 通訊作者。 Received February 2012, Accepted June 2012. 2012年2月送審 2012年6月通過。 252 Ghanbary et al.─Response variations of three trees species to flooding stress 研究報告 榿木、楊樹及落羽杉苗木在淹水環境下生長變異之研究 Ehsán Ghanbary,1) Masoud Tabari,1,4) Francisco García-Sánchez,2) Mehrdad Zarafshar,1) Maria Cristina Sanches3) 摘 要 榿木(Alnus subcordata)是分佈於伊朗北部Hyrcanian河灘森林的本土樹種。在過去數十年間，此樹 種與引進的楊樹(Populus deltoides)及落羽杉(Taxodium distichum)廣泛地被用來作為河灘低漥地的造林 樹種。然而此三種對淹水的容忍度以及其因應洪水的潛在機制目前仍不明瞭。基於此，本研究針對此三 樹種的幼苗進行為期120天的戶外試驗，以探討在不同淹水情況下其生長及型態生理的變異情形。所採 取的處理計有：1.不淹水(對照)；2.淹水至3 cm深；3.淹水至15 cm深等三種，並在試驗結束後進行存活 率、生長情形與相關的代謝參數量測。結果顯示，三種苗木在淹水環境下的存活率均相當高，但是其根 系長度、累積生物量以及葉綠素含量則有減少或降低的現象。落羽杉幼苗的徑生長量在淹水情況下有增 加的現象，其他兩種苗木則呈現相反的情形。淹水會使榿木及楊樹的葉面積、比葉面積以及高生長呈現 降低的現象，但對落羽杉卻無顯著的影響。此外淹水還會誘發此三種幼苗形成肥大的皮孔及不定根， 但根和葉的脯氨酸濃度則不受影響。由於本試驗所選定的三種樹種在淹水120天後的存活率均相當高 (>90%)，因此研究結果清楚地證實此三種樹種可作為 Hyrcanian 林地濱水帶和河灘地的造林樹種。 關鍵詞：不定根、造林、淹水容忍度、葉面積、脯氨酸、存活率。 Ghanbary E、Tabari M、García-Sánchez F、Zarafshar M、Sanches MC。2012。榿木、楊樹及落 羽杉苗木在淹水環境下生長變異之研究。台灣林業科學27(3):251-63。 INTRODUCTION Continuous or temporary flooding of for- however, is very slow, and the supply of O2 est ecosystems, which occurs commonly as a to roots is limited. Flooded trees are injured result of overflowing of rivers, storms, con- much more by stagnant water (which contains struction of dams, and overirrigation, leads less O2) than by moving water, as moving to soil anaerobiosis and consequent negative water has a higher oxygen concentration due ecological effects. Roots of plants need to to the permanent mixture of deep and shallow have a constant supply of O2 to provide the water layers (Glenz et al. 2006). In fact, even aerial parts with adequate amounts of wa- the most flood-tolerant species (e.g., Taxo- ter, mineral nutrients, and certain hormonal dium distichum) may be injured by standing growth regulators, among other compounds. water (Kozlowski and Pallardy 1997). Flood- When a soil is flooded, the water occupies the ing is an unavoidable environmental stress for previously gas-filled pores, and gas exchange seedlings in the plains and riparian areas and between the soil and air is restricted to mo- may affect normal plant functioning (Jackson lecular diffusion in the water of the soil (Ko- and Colmer 2005). Flooding of soils during zlowski and Pallardy 1997). Such diffusion, the growing season may affect woody plants Taiwan J For Sci 27(3): 251-63, 2012 253 at all stages of development. Typical respons- cumulation of some biochemical components, es of unadapted plants to flooding include including sugars, amino acids, and alcohols, inhibition of seed germination, decreases in in organs under environmental stresses is an survival and growth, massive losses of plant important feature of tolerant plants to this biomass, changes in plant morphology and condition (Morgan 1984). Proline is an amino anatomy, suppression of vegetative and repro- acid known as the most important osmolyte ductive growth, and often death (Kozlowski that accumulates under environmental stress 1997, Shiono et al. 2008). such as drought and salt stress (Roger 2003). Inundation of soil adversely affects shoot In spite of this, so far, accurate knowledge of growth of many species by inhibiting the the impacts of flooding on proline accumula- formation and expansion of leaves, reducing tion is not available, although García-Sánchez internode elongation, and inducing chlorosis, et al. (2007) reported that proline accumula- leaf senescence, and abscission (Kozlowski tion increased in roots under flooding but did 1997, Glenz et al. 2006). Flooding may in- not differ in leaves. crease or decrease the diameter growth of Flooding is a severe stress to trees, re- woody plants, is also followed by death and sulting in reduced species richness (Parolin decay of roots, and is often associated with and Wittmann 2010); furthermore, a correct reduced water and nutrient uptake and me- hydrologic regime is an important factor in tabolism (Dat et al. 2004). Responses of seed- seedling survival (Conner et al. 1986). lings to flooding reflect species’ habitats and Species of the Salicaceae, Betulaceae, growth patterns (Sakio 2005). and Taxodiaceae are utilized for riparian Factors that influence the flooding toler- restoration projects (Cao and Conner 1999, ance of plants include both biotic factors (e.g., Karrenberg et al. 2002, Francis et al. 2005). species, morphological and physiological ad- Alnus subcordata (L.) or Caucasian alder is a aptations, and development stage) (Kozlowski native, pioneer, hardwood, and fast-growing 1997, Bailey-Serres and Voesenek 2008) and tree species widely distributed in the Middle abiotic factors (e.g., the duration, depth, tim- East especially temperate areas of Iran and ing, and frequency of flooding) (Kozlowski the Caucasian Mountains. Likewise, in the 1997, Glenz et al. 2006). Most plants of Hyrcanian forest of northern Iran, which is flooded areas have adapted to flooding in one of the most ancient and unique forest various ecological and physiological ways communities in the world with 80 tree and (Pezeshki 2001). Mechanisms related to me- 50 shrub species in about 2 × 106 ha (Marvi- diating flooding tolerance include avoidance Mohajer 2007), A. subcordata is frequently strategies (e.g., formation of lenticels, aeren- found as a native species which grows on chyma, and adventitious roots) (Kozlowski colouvial soils. This species is also found in 1997, Dat et al. 2004, Glenz et al. 2006), es- wetlands, along streams and rivers, and at the cape strategies (e.g., enhanced shoot growth; bottom of valleys and plains (Sabeti 2006). Parolin 2002), physiological resistance strate- Taxodium distichum (L.) is known to be toler- gies (e.g., reduction in stomata conductance ant to flooding stress (Pezeshki and DeLaune and photosynthesis as well as root hydraulic 1998). This species is native to the US (Flor- conductivity; Parent et al. 2008), and de- ida) and has been introduced in Iran for plain creases in chlorophyll and protein levels region afforestation of Hyrcanian forests. (Kozlowski 2002, Yordanova et al. 2007). Ac- Populus deltoides (Bartr.) Marsh is native to 254 Ghanbary et al.─Response variations of three trees species to flooding stress North America (Florida, Texas, and Canada) pots, previously filled with a homogeneous and has been widely cultivated in Iran. The soil mixture taken from the Koloudeh nursery fast growth of these 3 species fulfills the ex- (sand: clay-loam of 1: 5 by volume, pH 8.4) tensive demand for wood for poles, pulp, and with no added fertilizer. After 20 d, the pots fuel in Iran. were transported to the Natural Resources Plant growth in floodplains is often campus, located at Tarbiat Modares Univ. subject to physical disturbances and physi- in the city of Noor, Mazandran Province ological water stress during