水深梯度对黑藻生长的影响

Response of Hydrilla verticillata in Growth to Water Depth Gradient

采用盆栽试验方法,将黑藻(Hydrilla verticillata)顶枝种植在水下0.5、1.0、1.5、2.0、2.5、3.0、3.5、4.0 m处塑料盆内,研究水深对黑藻生长的影响。结果表明,水深能够明显影响黑藻的存活,当水深>2.5 m时,由于光照不足,黑藻生长受到了明显抑制,水深3.0、3.5、4.0 m处黑藻分别于试验第57、33、21天死亡。水深改变了黑藻植株形态。水深对黑藻株高的影响极显著(P<0.01)。试验80 d时,不同水深处黑藻的茎节数、节间距、分枝数均差异显著(P<0.05)。试验80 d时,水深0.5～2.0 m处,黑藻株高和茎节数随水深增加而逐渐增加,当水深>2.0 m时,随水深增加开始减少。试验80 d时,水深0.5～2.5 m处,黑藻节间距随水深增加而不断延长。同一生长时间黑藻分枝数随水深增加而递减。各水深梯度处黑藻生物量呈先升高后降低的趋势,水深0.5～1.5 m处黑藻生物量随深度增加呈上升趋势,水深1.5 m处生物量最大,水深2.0、2.5 m处生物量迅速降低,不同水深梯度间黑藻生物量差异极显著(P<0.01)。该试验条件下,黑藻的光补偿水深在水体平均透明度(1.0 m)以下1.5～2.0 m之间。

To determine impacts of water depth on growth of Hydrilla verticillata,top branches or telomes taken from the plants were planted in plastic pots placed at water depths of 0.5,1.0,1.5,2.0,2.5,3.0,3.5 and 4.0 meters,separately.Results show that water depth significantly affected survival rate of H.verticillata.In water deeper than 2.5 meters,significant retardation of H.verticillata in growth was found due to shortage of light.With the water depth reaching 3.0,3.5 or 4.0 meters,H.verticillata died on D55,D33 and D21,separately.Moreover,water depth also altered morphological characteristics of H.verticillata.The effect was especially significant on plant height（P0.01） and on number of nodes,node spacing and number of branches as well（P0.05）.On D80 within the water 0.5-2.0 meters in depth,the plant height of H.verticillata and the number of nodes increased gradually with the depth,however,within the water deeper than 2.0 meters,they declined with depth.In addition,within the water 0.5-2.5 m in depth,the node spacing increased with depth on D80.At the same growth time the number of branches decreased with depth.Biomass of the plants,regardless of depth,showed a similar trend,that is,rising first and then falling.Within the water 0.5-1.5 m in depth,biomass of the plant increased with depth,and peaked at 1.5 m in depth.When the plant got as deep as 2.0 or 2.5 m,its biomass declined rapidly.Biomass of the plant varied sharply between depths（P0.01）.Therefore,under the experimental conditions as such,the light compensation depth for H.verticillata ranges from 1.5 to 2.0 meters below the water mean transparency（1.0 m）.