麻竹的花器官与繁育系统

Floral Organ and Breeding System of Dendrocalamus latiflorus

【目的】以我国南方重要经济竹种——麻竹为材料开展繁育系统的系统研究,以阐明竹类植物的开花特性及结实规律,为有效地开展杂交育种提供技术指导。【方法】对麻竹假小穗的解剖结构进行观察,野外定位观测假小穗的开花动态过程,通过花粉离体发芽试验测定花粉的活力及其寿命,采用联苯胺-过氧化氢法测定柱头的可授性,利用估算杂交指数(OCI)和花粉-胚珠比(P/O)的方法测定麻竹繁育系统的类型。【结果】麻竹假小穗可不固定地着生在不同级次的营养轴上,且其基部的2~3个潜伏芽可继续发育形成新小穗,故其花期较长,整个生长季均有续次开花现象;麻竹每一假小穗具7~10朵花,其在假小穗上的开放自上而下依次进行,单一假小穗从第1朵小花开放至全部小花完成开放需5~7天;而且雌雄异熟,同一小花雌蕊先于雄蕊1~4天成熟,通常假小穗只有上部3~4朵小花的柱头能伸出稃片外,而中、下部柱头不伸出,故只有假小穗上部的1~4朵小花可以授粉结实;麻竹柱头伸出的第1天便具可授性,第3~4天可授性最强,6天后萎缩;新鲜花粉萌发率差异较大,平均约为27%,高的可达54.6%;离体花粉不易保存,室温保存36 h萌发率降为3%左右;低温及干燥处理均不能延长花粉寿命,若将即将散粉的花药在4℃低温下保存,虽可适当延长储藏时间,但效果十分有限。【结论】杂交试验中,若将麻竹作为父本,应在花药散粉的当天完成授粉;若作为母本,应在柱头伸出的第1天就开展授粉。利用杂交指数和花粉-胚珠比综合判断,麻竹的繁育系统为"异交为主,部分自交亲和",但考虑到竹子为无性繁殖群体,同期零星开花最有可能发生在遗传背景一致的同一无性系,因此异株间的授粉也极有可能是具相同基因型个体间的交配,故竹子的有性繁殖应充分关注"近交衰退"现象。

【Objective】The breeding system of Dendrocalamus latiflorus was studied to detect its floral and seed-setting characteristics thus to facilitate its crossbreeding.【Method 】Pseudospikelet was anatomized,flowering process was observed in the field,pollen viability was determined by in vitro germination test,stigma receptivity was determined by benzidine-hydrogen peroxide,and the type of its breeding system was estimated by outcrossing index（OCI） and pollenovule ratio（P/O）.【Result】Pseudospikelet of D.latiflorus grows at rachises of different developing levels,and the 2-3latent buds at the base of each pseudospikelet would develop into new pseudospikelet,thus it blooms continuously during the growth season.7-10 florets grows on each pseudospikelet,those florets blooms from top to bottom during 5-7 days on each pseudospikelet,the pistil matured 1-4 days earlier than the stamen.Usually,only the 3-4 florets on the top would exerted from the hull while the rest would not,thus resulted in pollination and seed set on the top of each pseudospikelet.Stigma has pollen receptivity from the day it exerted out,and the receptivity becomes stronger on the 3^rd to 4^th day,followed with stigma wither and dry after 6 days.Fresh pollen germinated at an average rate of 27% with a peak of 54.6%;in-vitro preservation of pollen is difficult,3% germinated after 36 h at room temperature,low temperature anddrying treatment could not prolong its life.If anther were preserved at 4 ℃,the pollen life would last a little longer.【Conclusion】In crossbreeding experiment,if D.latiflorus was used as male parent,pollination should be conducted on the day that the pollen dispersed from the anther;if it was used as female parent,pollination should be conducted from the day that the stigma exerted from the hull.Based on the OCI of Dafni and the P/O of Cruden,the breeding system of D.latiflorus was given priority to outcrossing,and partial self-compatibility;however,bamboos are a group of plants with asexual reproduction,flowering plants at the same period may be clones with the same genetic background,so the pollination among different individuals may be selfing or inbreeding,thus ＂inbreeding depression ＂should be avoided during the sexual reproduction of bamboos.