干旱胁迫对黄土高原4种蒿属植物叶形态解剖学特征的影响

以黄土高原演替初期阶段的猪毛蒿(Artemisia scoparia Waldst.et Kit.)、茭蒿(Artemisia giraldii Pamp.)、铁杆蒿(Artemisia gmelinii Web.ex Stechm.)3种优势种和1种常见种黄花蒿(Artemisia annua Linn.)为供试材料,采用盆栽试验与称重控水法,将土壤含水量分别控制在田间最大持水量的75%(适宜水分对照)、55%(中度干旱)和35%(重度干旱),研究干旱胁迫对菊科蒿属植物叶片形态解剖学的影响,揭示植物叶片生态适应机制,为生态恢复过程中植被演替的规律提供理论依据。于植物营养生长末期选取代表性的叶片,分别采用电子扫描显微镜、电子透射显微镜和光学显微镜对叶表皮特征、亚细胞显微特征和组织结构进行观察。结果表明:干旱胁迫下,这4种植物表现为不同程度的叶片增厚、栅栏组织厚度、叶片紧实度和角质层厚度增加;3种旱生型植物猪毛蒿、茭蒿和铁杆蒿的叶片下表皮具有浓密的表皮毛,有利于防止水分过度蒸腾,而中生型黄花蒿叶片无此功能;铁杆蒿和黄花蒿上表皮毛稀少,不利于保水和防止强光照,干旱胁迫下依靠降低上表皮气孔密度和叶细胞叶绿体数目来适应环境;茭蒿和猪毛蒿叶绿体形态相似,具有较厚的基粒和浓密的基粒片层,强光下容易引起氧化损伤,猪毛蒿通过浓密的上表皮毛而茭蒿通过较强的抗氧化机制防止光能过剩,两者在重度干旱下均产生大量脂质体。4种蒿属植物中黄花蒿的叶片解剖学特征受到干旱的影响变化最大,铁杆蒿和猪毛蒿次之,茭蒿最弱,3种优势种的干旱适应性显著强于黄花蒿,干旱下叶片解剖学的结论与干旱耐受性指标结果一致。

Effect of drought on leaf anatomical characteristics of four Artemisia species in the Loess Plateau

Leaf anatomical characteristics of 4 Artemisia species under drought conditions were investigated to reveal the drought-resistant strategies of vegetation at early stage of ecological succession in the Loess Plateau. Three dominant species as Artemisia scoparia Waldst. et Kit., Artemisia giraldii Pamp. and Artemisia gmelinii Web. ex Stechm. and one common specie, Artemisia annua Linn. during early succession in the Loess Plateau were selected to investigate the leaf anatomical adaptation of Artemisia to soil drought stresses. Pot experiment was adopted to control the soil water content. And 75%, 55% and 35% of field moisture capacity were set as control, moderate water stress and severe water stress, respectively. The latest mature leaves were freshly collected and fixed at the end of their vegetation growth period for SEM, TEM and the optical microscope. We analyzed the difference among leaf epidermis characteristics of the four Artemisia species according to the sub-cellular micro characteristic and the organizational anatomical structure. The results show that: the four Artemisia leaves have some kind of anatomy characteristics, as blade thickness, palisade tissue thickness, cutin layer thickness, ratio of palisade tissue thickness to sponge tissue thickness, tightness of leaf tissue structure were increased under drought conditions. Leaf epidermises of A. scoparia, A. giraldii and A. gmelinii have dense trichomes to prevent excessive water loss from evaporation; however A. annua has sparse trichomes. The upper epidermises of A. gmelinii and A. annua are sparse, which are not good for water conservation and to prevent highlight, the decrease of the stoma density and the number of chloroplast were conducted to adapt environment change. Similar chloroplast anatomy characteristics of thick grana and dense grana lamellae were observed in the leaf cells of A. scoparia and A. giraldii, which are easier to result in oxidative damage during photosynthetic process. To prevent the oxidative damage, the dense trichomes on upper epidermises of A. scoparia and outstanding antioxidant mechanisms of A. giraldii were conducted, and a large number of liposomes were also produced in the two species. The leaf anatomical characteristics influence of drought affected on the A. annua was the greatest between the four Artemisia species, and A. gmelinii and A. scopara were followed, the least affect was on Artemisia giraldii. The three dominant species had stronger ability to adapt to drought stress than the common species-Artemisia annua. The leaf anatomical characteristics and drought tolerance indexes of the 4 species represented similar comments of drought tolerance ability.