【作者】 苏俊霞；

【导师】 林鉴钊； 李楠；

【作者基本信息】 广西大学 ， 作物栽培学与耕作学， 2004， 硕士

【摘要】 本研究主要采用生长观测以及显微技术的方法对5种苏铁羽叶和羽片的生长发育过程中的形态变化、生长速度、羽片组织的分化、表皮和气孔器的发育以及气孔密度作了详细的观察和研究，旨在为苏铁的分类、保护、化石的鉴定、以及探讨苏铁类植物的演化提供一些新的证据，同时为苏铁的栽培提供一定的理论指导。 不同苏铁羽叶的生长模式不一致。苏铁属的幼叶卷叠式比较相似：3种苏铁整个幼羽叶的纵向卷叠式属直立型，水平的卷叠式为内卷型，单个羽片属拳卷型。泽米铁科两种苏铁幼羽叶的纵向卷叠式亦属直立型，一列羽片内的羽片之间为蔽后式排列，单个羽片为扁平状。合意苏铁水平的卷叠方式为对折型，而大型双子铁不为对折型。 掌握了五种苏铁羽叶羽片的生长发育特点，为苏铁栽培、管理和病虫害防治提供了一定的理论指导。发现羽叶和羽片的伸长期与它们成熟时的大小成正相关。 五种苏铁羽片的维管束具有相似的发育过程，初生木质部和初生韧皮部的发育方式均为外始式，次生木质部数量极少，位于原生木质部的远轴面。苏铁属羽片组织分化初期比较相似(仅在德保苏铁主脉中见到黏液道)，后随着组织的进一步分化种间差异明显：德保苏铁在叶肉组织及主脉同化组织中出现异细胞；石山苏铁叶肉组织在成熟的过程中出现了晶簇；组织分化早期种间下皮层细胞分布有明显差 厂一西人‘学硕价老丈 异;3种苏铁栅栏组织层数不同。大型双子铁和合意苏铁的差异也很 明显，主要体现为:勃液道和维管束排列方式不同(前者劲液道和维 管束为相对排列，而后者为相间排歹lJ;同一发育时期，染色较深的异 细胞在两个种的分布不一致;成熟时，含晶细胞在叶肉组织的分布不 同;同一种苏铁不同发育时期，异细胞的分布也不一致。 五种苏铁的保卫细胞和副卫细胞分别起源于不同的原始细胞， 气孔器发育类型属单唇形。苏铁属的3种植物表皮及气孔器的发育差 异不太明显:表皮细胞在近成熟时外壁上均出现单纹孔，多沿垂周壁 分布;保卫细胞发育初期不下陷，近成熟时下陷于1一2层细胞之下; 有气孔簇出现，每个气孔簇均有2个气孔器组成，它们起源于2个相 邻的保卫细胞母细胞;有早熟气孔器，多出现在近主脉的位置;毛基 为单细胞或两细胞，发育初期的毛基种间无明显差别，成熟时出现明 显差异。 泽米铁科两个种与苏铁属的差异较明显。它们的毛基只分布于叶 缘。这两种苏铁的表皮细胞及气孔器在发育初期差别不大，表皮近成 熟时分化为两种类型细胞，即厚壁细胞和薄壁细胞，外壁上均没有纹 孔。大型双子铁的保卫细胞母细胞已经下陷，成熟时气孔器下陷于3一 4层细胞之下，最外层细胞突出于表皮;合意苏铁的保卫细胞母细胞 与表皮在同一平面上，成熟时保卫细胞下陷于2一3层细胞之下。五 种苏铁保卫细胞的下陷均是由于畜lJ卫细胞平周分裂而致。 不同苏铁具有不同的气孔密度峰值。不同发育时期，羽片不同部 位气孔密度相差很远，但是在羽片停止伸长时，各个部位的气孔密度 厂一西人一学硬士忿丈基本接近。 通过对五种苏铁羽叶和羽片发育过程中形态的观察以及气孔器发育和气孔密度的研究表明，羽叶和羽片发育顺序为向顶式。更多还原

【Abstract】 The growth and development of frond and pinna in five species of cycads was studied by growth observation and microscopy of tissue development. This study observed morphological change , growth rate, tissue differentiation of pinna ,and stomatal ontogeny and stomatal density of epidermis. It could provide clue for cultivation of cycad and provide information for taxonomy, conservation, evolution and identification of their fossil.These cycad species had different growth patterns. The longitudinal ptyxis of the whole leaf was erect. The horizontal ptyxis was involute in Cycas, conduplinate in Encephalartos. The individual pinna was circinate in Cycas, flat in Dioon and Encephalartos.Tlie pinna in each side of a frond overlapped each other succubously in Dioon and Encephalartos.The growth and development of frond in these observed species showed clear positive correlation between the elongation’s time of frond, pinna and their mature size.The development of vascular bundle was similar in these species: both primary xylem and primary phloem were exarch, and the secondary xylem was near the phloem. The studied species hadsimilar leaflets structure initially and became distinct during their development. Cycas debaoensis had idioblasts both in mesophyll tissue and assimilation tissue of midrib. Cycas miquelii had druse crystals in the mature mesophyll tissue. The three Cycas species were different in the structure of hypodermal cells and palisade tissue. Dioon spinulosum and Encephalartos gratus were different in the arrangement of mucilage canal and vascular bundle(the former is corresponding, but the latter is alternate), distribution pattern of idioblasts and drusecrystals. Idioblasts occured in different tissue in different developmental stages.The somatal ontogeny was haplocheilic as the guard cells(GC) and subsidiary cells(SC) developed from different mother cells in the observed species. The three Cycas species showed no notable differences in the development of epidermis and stomata. When the epidermis became mature, rounded or oval pits developed on cell periphery, near to the anticlinal walls . The guard cells started to sunk one or two cell layers with the development. Two stomata apparatus occurred side by side forming stomata clusters and arised from two adjacent CMC. Premature stomata apparatus were often present near the midrib. Hair bases were composed of one or two cells. They were similar initially and became distinct with development.Hair bases in Dioon spinulosum and Encephalartos gratus occurred only in leaf margin. Their epidermis and stomata were similar in early developmental stages. Mature epidermis cnosisted of two category of epidermal cells with thick or thin walls respectively. No pits were observed in the surface wall. The GMC in Dioon spinulosum was sunken below the surface in epidermis but in Encephalartos gratus it did not occur. The mature guard cells were deeply sunken to form a three or four cell layer deep pit in the former but two or three cell layer deep pit in the latter. The periclinal division of SC brought out the GC sunk.Stomatal density peaked differently in different species. But ,in one species stomatal density varied dramatically from the base to the tip in the initial developmental stage and became evenly distributed in the end.The results from the study of morphology, ontogeny of epidermis and stomata and stomatal density showed that the leaflets in the observed species matured acropetaly.更多还原