轻简化基质育苗棉苗栽前离床期耐受生理特性研究

Study of the Tolerant Physiology of Cotton Seedlings Nursed with Simplified Techniques after Removal from the Seedling Bed

【目的】明确棉花轻简化基质育苗技术下的幼苗离床耐受生理相关特性,为其安全存放和运输保护提供理论支持。【方法】设置了育苗基质添加保水剂和不添加保水剂的处理,以中棉所50为材料,研究了29 d苗龄的幼苗不同离床和复水条件下的相关生理指标变化。【结果】室内条件下棉苗离床的耐受过程中,幼苗叶片逐步失水,引起从叶片外部表层细胞结构到内部生理的一系列变化,最终影响移栽成活率。其中,离床3 d内是安全期,叶片含水量的损失不到5%,且及时复水后能达到幼苗离床前初始状态的98%以上,移栽成活率均在99%以上;此时叶片表层细胞结构相对完整,细胞连接相对平滑,保卫细胞相对饱满。离床5 d为临界期,此时复水仅能达到初期的93%左右;第5至7天叶片失水最快,这个阶段相对含水率日均下降15百分点;当失水降到50%以下(11 d后)时,叶片表层细胞皱缩较严重,细胞壁皱褶明显,气孔塌陷较深,复水后恢复能力弱。失水过程中真叶内脯氨酸、丙二醛含量和过氧化物酶活力随离床时间增加而上升/增加,过氧化氢酶和超氧化物歧化酶活力变化在前5 d上升,5 d后开始下降。【结论】保水剂有利于维持离床棉苗体内水分,缓解离床期干旱胁迫。

[Objective] The primary target of this experiment was to illustrate the tolerant physiological characteristics of cotton seedlings nursed with simplified techniques after removal from the seedling bed to show theoretical support for these techniques in terms of safe storage and protection during transportation. [Method] Plants of the cotton variety CCRI 50 were grown in nursing substrate with（W） and without（0） an added water-retaining agent. Physiological indexes of cotton leaves were tested,and the cellular structure of the leaves was observed with the scanning electron microscope. [Result] The results showed that the leaf relative water content（LRWR） decreased to 95% in 3 d under the two treatments but could return to 98% when the seedlings were rewatered and that the survival rate following transplanting was above 99%. Scaning electron microscopy indicated that the cellular structure of the leaves was quite integrated, with a continuous and smooth surface. Additionally, the cell junction was natural and stomata guard cells were relatively well-stacked. Five days after removal from the seedling bed was the demarcation line for the activity of cotton seedlings, with LRWR decreasing by 10 percentage points and only reaching 93% when rewatered. From 5 d to 7 d, when the seedlings were removed from bed, the leaf gradually suffered increasing drought stress and water in the leaf was lost quickly. This lead to a decrease in the LRWR at a rate of up to 15 percentage points per day. By 11 d,the LRWR had dropped to 50%, the cells of the outer leaves had shrunk severely, the cytoderm was folded and overlapped, and the guard cells had collapsed, indicating that water loss dramatically weakened the recovery capability of these plants. The proline and malondialdehyde contents of the seedlings increased during their removal from the beds, and the activity of peroxidase increased. The activity of catalase and superoxide dismutase increased during the first 5 d before decreasing again. [Conclusion]The inclusion of a water-retaining agent in the nursing substrate will help to maintain water level in the plants that can help relieve drought stress associated with the bed-away-seedlings.