干旱胁迫下油橄榄品种光合特性研究

为揭示油橄榄(Olea europaea L.)耐旱性与光合特性之间的关系,以筛选出的适宜于半干旱川西南地区种植的7个引进油橄榄品种为供试材料,采用盆栽模拟干旱胁迫的方法,研究持续干旱胁迫对其光合特性的影响。结果表明:(1)随着干旱胁迫程度加剧,7个油橄榄品种叶片相对含水量均显著降低,至干旱胁迫后期(25d),各品种叶片均出现大幅失水,其中品种‘科拉蒂’失水率最高(45.79%),而品种‘小苹果’失水率最低(25.52%),说明‘小苹果’叶片在干旱胁迫下较其他油橄榄品种具有更高保水能力。(2)随着干旱胁迫程度加剧,7个油橄榄品种叶片光合色素含量均不同程度降低,表明光合色素分解量大于合成量;干旱胁迫持续25d时,品种‘豆果’的叶绿素a和叶绿素b含量下降幅度最大(P0.05),品种‘皮削利’类胡萝卜素含量下降幅度最大(P0.05),而品种‘小苹果’叶绿素a含量下降幅度最小。(3)随着干旱胁迫的持续进行,各油橄榄品种叶片净光合速率(Pn)、蒸腾速率(Tr)、气孔导度(Gs)和胞间CO2浓度(Ci)均不同程度降低,而水分利用效率(WUE)则呈上升趋势;干旱胁迫期间,品种‘佛奥’的Pn、Tr和Ci以及‘皮削利’的Gs降幅均高于其他品种,而‘小苹果’的Pn、Gs和Ci降幅均为最小且WUE上升幅度最大。研究发现,在持续干旱胁迫条件下,油橄榄幼苗叶片均大幅失水,光合色素结构被破坏、色素分解、含量降低,同时气孔关闭蒸发减少,光合作用减弱,而供试油橄榄品种中‘小苹果’对干旱胁迫的适应性最强,适宜于在半干旱的川西地区种植。

Photosynthetic Characters of Different Introduced Olive Varieties under Drought Stress

Olive (Olea europaea L.) is one of the four famous woody oil species across the world with important nutritional and pharmaceutical values. In order to reveal the relationship between drought resistance and photosynthesis characteristics, we conducted pot experiments to investigate the effect of drought stress on the photosynthetic characteristics of seven introduced olive varieties including Picholine, Picual, Manzanillo, Koroneiki, Frantoio, Arbequina and Coratina, which had been filtered the suitable for growth in the semi arid region of the Southwest of Sichuan Province. The results showed that: (1) the leaf relative water content (LRWC) of all the tested olive varieties was significantly reduced with the intensification of the degree of drought stress (P<0.05); At the later period of stress (25 days), the cultivars showed different levels of wilting symptom compared to control. Among them, Coratina showed the highest water loss rate while Manzanillo slightly affected, indicting the Manzanillo leaves exhibited a higher water retaining capacity compared to other cultivars under drought stress. (2) The concentrations of photosynthetic pigment in all the tested olive varieties were significantly decreased with the increasing duration of drought stress (P<0.05), which was mainly resulted from the rapid degradation of chlorophyll than biosynthesis; the Chla and Chlb contents in Arbequina, as well as Car content in Picholine were significantly declined after 25 d drought stress (P<0.05), while the Chla content of Manzanillo was not decreased obviously (P>0.05). (3) The photosynthetic parameters of the cultivars varied in response to drought stress. Net photosynthetic rate (P_n), transpiration rate (T_r), stomatal conductance (G_s) and intercellular CO₂ concentration (C_i) in leaves decreased, while the water use efficiency (WUE) increased with the drought. In addition, the drop of P_n, T_r and C_i of Frantoio and G_s of Picholine were higher than those of other varieties, while slightly decreased in P_n, G_s and C_i and sharply increased in WUE was observed in Manzanillo. Our research showed that under the persistent drought stress the olive seedling leaves were substantial loss of water and the photosynthetic pigment structure was destroyed and decomposed, as well as stomatals closed and photosynthesis decreased. Among the tested olive varieties, Manzanillo shows excellent adaptability to drought stress and is suitable for planting in the semi arid region of the Southwest of Sichuan Province.