巨龙竹笋-幼竹期秆形发育的组织解剖学研究

巨龙竹( Dendrocalamus sinicus Chia et J. L. Sun)是云南特有的珍稀木本丛生竹,其秆形分为通直型和弯曲型两种变型。为了揭示巨龙竹不同秆形的组织结构特征,本文通过定点观测0 ~ 49 d的巨龙竹笋和幼竹生长发育状况,并采用石蜡切片技术对笋期0 ~ 45 d内样品的组织结构进行比较解剖学研究。结果显示:(1)巨龙竹在笋-幼竹(0 ~ 49 d)发育期,秆高生长呈“慢-快”的趋势,21 ~ 35 d时弯曲型茎秆开始显现,易于辨别;(2)5 ~ 30 d时,弯曲型茎秆中维管束的发育早于通直型;对比弯曲型茎秆内外两侧维管束,内侧维管束导管内径较小,但纤维鞘中的纤维细胞层数更多;(3)弯曲型茎秆中薄壁细胞的分化早于通直型,20 d后弯曲型茎秆中的薄壁细胞出现明显的可被番红-固绿染色的细胞核,并呈有规律的排列;弯曲型茎秆内侧薄壁细胞稍小于外侧薄壁细胞,但内侧被染色细胞核的薄壁细胞多于外侧。研究结果表明巨龙竹弯曲型茎秆性状在笋期第21 ~ 35 d内即可通过茎秆形态判别,弯曲型茎秆中维管束的发育以及薄壁细胞分化均早于通直型茎秆,同一时期弯曲型茎秆内侧细胞分裂较外侧旺盛、维管束木质化程度更高。

Tissue development of culm in Dendrocalamus sinicus from shoot to young culm stage

Dendrocalamus sinicus Chia et J. L. Sun, a rare bamboo species endemic to Yunnan Province in China, is one of the strongest woody bamboo species in the world. It occurs as two variants, i.e ., straight-culmed variant (SC) and bent-culmed variant (BC). To reveal the anatomical basis of SC and BC, we collected data on culm height and morphological characteristics of shoots and young culms (emerged from ground for 0 - 49 d) from six clumps of D. sinicus . In addition, shoot and young culm development (0 - 45 d) were observed using comparative anatomy based on paraffin sectioning. Results showed that culm-height growth exhibited a “slow-fast” pattern, and the BC morphological character clearly appeared at 21-35 d, which was distinct from that of SC. The development of vascular bundles occurred earlier in BC (5-30 d) than in SC. Within BC, compared with the outer vascular bundles, the inner vascular bundles possessed smaller diameters and more fibrocytes in the fibrous sheath. Parenchyma cell differentiation occurred earlier in BC than in SC. Nuclei dyed with Safranine and Fast Green appeared in the parenchyma cells, which became regularly arranged from 20 d in BC. The parenchyma cells in the inner culm of BC were slightly smaller than those in the outer culm, whereas there was a greater number of parenchyma cells with dyed nuclei in the inner culm than in the outer culm. These results showed that the bent culm shape in BC can be identified by culm morphology during 21-35 d. The development of vascular bundles and differentiation of parenchyma cells occurred earlier in BC than in SC. Furthermore, compared with the outer culm in BC at the corresponding period, cell divisions in the inner culm were more vigorous and the degree of vascular bundle lignification was also higher.