不同光照强度对新娘草叶片形态建成及超微结构的影响

为探究新娘草叶片对光照变化的形态建成和超微结构的响应机制,以新娘草茎段扦插苗为试验材料,通过遮阳网人工模拟5种光环境(遮光度分别为0、25%、50%、75%、95%)进行试验,研究不同光照强度对新娘草叶片生长及超微结构的影响。结果表明:随光强的减弱,新娘草叶长、叶宽和叶面积呈先增后减的变化趋势。在遮光75%时,叶长、叶宽和叶面积达到峰值,叶面颜色由黄绿色变为浓绿色,叶背颜色由深紫色变为浅紫色,在遮光95%时,紫色消失。光强对叶绿素a(Chl a)、叶绿素b(Chl b)、叶绿素a+bChl (a+b)]和花色素苷(Ant)含量均有显著影响(P<0.05):Chl a、Chl b和Chl (a+b)含量与光强呈负相关,Ant含量与光强呈正相关。新娘草叶片厚度、上表皮厚度、下表皮厚度、栅栏组织厚度、海绵组织厚度均随光强的降低而显著降低(P<0.05),而栅栏/海绵组织厚度和组织密实度均在50%遮光下达到峰值。全光及遮光25%条件对叶肉细胞的超微结构产生了轻微的破坏,造成部分基粒类囊体片层和基质类囊体片层的扩张,淀粉粒体积变大,而极端弱光(遮光95%)对叶肉细胞的超微结构产生了巨大的破坏,使得部分叶绿体解体,淀粉粒空洞。研究结果表明新娘草具有较强的光适应性,可以通过调整叶形、叶色、叶片解剖结构的方式适应不同的光环境,适度的光照强度(遮光50%~75%)有利于新娘草维持最佳的生长状态,而在极端弱光环境(遮光95%)下新娘草虽能存活,但叶片内部器官的结构产生了不可逆的损伤。

Effects of different light intensities on morphogenesis and ultrastructure of Gibasis pellucida leaf

In this research, ramets of Gibasis pellucida propagated from stem cuttings were used as experimental material to explore the morphological and ultrastructural changes in leaves, when grown at different light levels. Shading net was used to create a series of five light environments with 0, 25%, 50%, 75% and 95% shading, respectively. The results indicated that: with reducing light level from 0 to 75% shading, leaf length, width and area progressively increased to a maximum for the experimental material at 75% shading. Along with change in leaf size, the colors of the leaf upper surface changed from yellow-green to dark-green, and that of the leaf lower surface changed from deep-purple to light-purple. When the shading intensity was 95%, the purple color disappeared. Leaf chorophyll a, chlorophyll b, and chlorophyll (a+b) contents were negatively correlated with light intensity (P<0.05), while leaf anthocyanin content was positively correlated with light intensity. The thickness of leaves and their upper epidermis, lower epidermis, palisade tissue and spongy mesophyll tissue decreased significantly with decreasing light intensity (P<0.05), while the ratio of palisade:spongy mesophyll thickness, and tightness of tissue were highest in the 50% shade treatment. The 0 and 25% shade treatments slightly damaged the ultrastructure of mesophyll cells, causing the expansion of some thylakoid grana and stroma, and enlargement of starch grains. Extremely low-light intensity (95% shading) resulted in serious disruption to the ultrastructure of mesophyll cells, together with some chloroplast disintegration and emptying of starch grains. In summary, G. pellucida possesses a very strong shade adaptation response, and mechanisms used to adapt to the different light environments involved adjusting the shape, pigmentation and anatomical structure of leaves. While G. pellucida could survive in the extremely low light environment of the 95% shade treatment, the structure of the leaf internal organs was damaged irreversibly by this degree of shading.