汪婷 张霞 周存宇 胡双双 唐雨 杨朝东

摘 要： 水花生（Alternanthera philoxeroides）因其表型可塑性、高生长速率和快速无性繁殖能适应水、陆生境。该文利用光学显微镜和荧光显微镜对水、陆生境的水花生不定根、茎解剖结构、组织化学特征及质外体通透性进行了研究。结果表明：（1）水生境下，其不定根皮层中具较大裂生型通气组织，无次生生长，内皮层具凯氏带且栓质化，皮层和皮下层明显木质化。（2）在陆生环境下，其不定根有次生生长，胞间具通气组织，内皮层具凯氏带且栓质化，皮层和皮下层略木质化;此外，不定根还具额外形成层，产生次生维管束、薄壁组织和不定芽;多年生不定根中具直接分裂的薄壁组织，周皮具凯氏带，且栓质化和木质化。（3）水、陆生境下，其匍匐茎具髓和中空髓腔，发生次生生长，具裂-溶生型通气组织、单层内皮层、厚角组织和木质化且栓质化的角质层，陆生匍匐茎周皮栓质化且木质化。（4）水花生质外体屏障结构组成复杂，黄连素无法穿透质外体屏障结构。水花生的上述解剖学特征，是水花生适应水、陆生境的有力证据。

关键词： 水花生， 组织化学染色， 质外体屏障结构， 通透性， 额外形成层， 通气组织

Abstract： Alligator weed （Alternanthera philoxeroides） adapts to both aquatic and terrestrial habitats due to its phenotypic plasticity， high growth rate and asexual reproduction. The anatomical structure， histochemical characteristics， and apoptotic permeability of adventitious roots and stems of A. philoxeroides growing at aquatic and terrestrial habitats were studied using light and fluorescence microscope. The results were as follows： （1） The aquatic adventitious roots had a large schizogenous aerenchyma in cortex， casparian bands， suberin lamellae and lignin on the endodermis， heavily lignified in cortex and hypodermis and without secondary growth. （2） The terrestrial adventitious roots had secondary growth， with intercellular aerenchyma in cortex， casparian bands， suberin lamellae and lignin on the endodermis， slightly lignified in cortex and hypodermis; Additionally， the terrestrial adventitious roots had supernumerary cambia which produce secondary vascular bundles， parenchyma and adventitious buds; The old perennial adventitious roots possessed dilated parenchyma， and periderm had casparian bands， suberin lamellae and lignin. （3） The stolons in both aquatic and terrestrial habitats had pith， pith cavity， endodermis， collenchyma， and secondary growth， with schizo-lysigeny aerenchyma in cortex， and cuticle with suberin lamellae and lignin. The periderm possessed suberin lamellae， and lignin in the terrestrial stolons. （4） The apoplastic barriers were found in roots and stems of A. philoxeroides， which had a complex structure， and berberine can not penetrate these apoplastic barriers. The above anatomical characteristics identify the adaptation of A. philoxeroides to both aquatic and terrestrial habitats.

Key words： Alternanthera philoxeroides， histochemical staining， apoplastic barrier， permeability， supernumerary cambia， aerenchyma

水花生（Alternanthera philoxeroides）， 苋科，莲子草属，原产南美洲温带，在亚热带和温带水生和旱生环境中均有分布。水花生因对非生物胁迫因子具表型可塑性，能快速无性繁殖入侵不同生境（娄远来等，2004; 付文竹等，2006; Geng et al.， 2006; Pan et al.， 2006; Liu & Yu， 2009; 陈中义等，2010），在中国被视为一种入侵植物（潘晓云等，2007; 陳立立等，2008）。水花……