Potencial hídrico
International Baccalaureate · IB Diploma · Biology · HL Tópico 34 5:06 Narração em inglês · Legendas em inglês + 中文 gravadas
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Transcrição
A plant cell can stop gaining net water even while its contents contain solute.
植物细胞即使内部含有溶质，也可能停止净吸水。
The cell wall permits pressure to build, altering the water-potential 水势 balance.
细胞壁允许压力积累，从而改变水势平衡。
Water potential describes the tendency of water to move relative to a chosen reference, with pressure units.
水势描述了水相对于选定参考点的移动趋势，以压力单位表示。
In the simplified cell model, water potential equals solute potential plus pressure potential.
在简化的细胞模型中，水势等于溶质势加上压力势。
Dissolved solute lowers solute potential; positive pressure can raise water potential.
溶解的溶质会降低溶质势；正压可以提高水势。
Net water movement through a water-permeable membrane is from higher to lower water potential.
通过透水膜的水净移动是从高水势向低水势方向进行。
Water potential is a pressure-equivalent measure of the tendency of water to move relative to a reference.
水势是相对于参考点衡量水移动趋势的压力当量指标。
Pressure potential is the pressure contribution to water potential in the stated model.
压力势是该模型中水势的压力贡献部分。
Compare the complete water potentials of the two sides rather than solute concentrations alone.
比较两侧完整的水势，而不仅仅是溶质浓度。
A turgid cell can have the same total water potential as its surroundings despite unequal solute potential.
尽管溶质势不相等，一个膨胀的细胞仍可能与其周围环境具有相同的总水势。
At equilibrium there is no net transfer, but water molecules can continue moving in both directions.
在平衡状态下，没有净转移，但水分子仍可继续向两个方向移动。
In the lab: Use provided potential values and labelled plant-cell models.
在实验室中，使用提供的电势值和标注的植物细胞模型。
State the reference and units before adding components.
添加成分前，需说明参考点和单位。
For school tissue investigations, control temperature, tissue dimensions, time and blotting, and estimate a zero-change point from repeated measurements.
针对学校组织研究，应控制温度、组织尺寸、时间和吸纸操作，并通过重复测量估算零变化点。
Do not claim the mass method separately measures cell pressure without further evidence.
若无进一步证据，不可声称质量法能单独测量细胞压力。
Known: a cell has solute potential negative 0.8 MPa and pressure potential plus 0.3 MPa, so total potential is negative 0.5 MPa.
已知：某细胞的溶质势为负0.8 MPa，压力势为正0.3 MPa，因此总水势为负0.5 MPa。
Surrounding solution is negative 0.2 MPa.
外界溶液的水势为负0.2 MPa。
Water tends to enter the cell because negative 0.2 is higher than negative 0.5.
由于负0.2高于负0.5，水倾向于进入细胞。
If the cell components change to negative 0.8 and plus 0.6 MPa, its total is negative 0.2 MPa, matching the surroundings in this simplified model.
若细胞组分变为负0.8和正0.6 MPa，则其总水势为负0.2 MPa，在此简化模型中与外界环境相等。
Your turn: Solute potential is −0.7 MPa and pressure potential is +0.4 MPa.
请作答。 溶质势为负0.7兆帕，压力势为正0.4兆帕。
Find total water potential.
求总水势。
Pause the video and work it out.
请暂停视频，自己算一算。
Check: minus 0.7 plus 0.4 is a water potential of minus 0.3 megapascals.
核对：−0.7 + 0.4，水势为 −0.3 兆帕。
More negative is lower, not higher.
更负代表更低，而非更高。
The additive cell model has stated boundaries and does not require pretending that every real tissue has one uniform value.
加性细胞模型具有明确的边界，无需假设所有真实组织都具有单一均匀的值。
Loss of turgor and cell-wall support differ from a rigid wall directly controlling solute concentration.
膨压丧失与细胞壁支撑作用，不同于刚性壁直接控制溶质浓度。
Not true: Solute concentration alone always determines water movement in a turgid plant cell.
这种说法不正确。 溶质浓度并不总是单独决定膨压植物细胞中的水分移动。
In a turgid cell the wall pushes back: pressure potential opposes the solute effect, and movement depends on the SUM.
在膨压细胞中，细胞壁会产生反作用力。 压力势会抵消溶质势的影响，水分的移动取决于两者的总和。
Solute concentration alone decides only when pressure potential is zero.
只有当压力势为零时，溶质浓度才会单独起决定作用。
Water potential describes the tendency of water to move relative to a chosen reference, with pressure units.
水势描述水相对于选定参考点的移动趋势，单位为压力单位。
Compare the complete water potentials of the two sides rather than solute concentrations alone.
比较两侧完整的水势，而非仅比较溶质浓度。
Watch for: more negative is lower, not higher.
注意：更负的值表示更低，而非更高。
Solute potential is minus 0.9 MPa and pressure potential is plus 0.2 MPa.
溶质势为 -0.9 MPa，压力势为 +0.2 MPa。
The surrounding solution is minus 0.4 MPa.
周围溶液的势为 -0.4 MPa。
Find the cell's water potential and the direction of net water movement.
求细胞的水势以及净水分移动的方向。
The result is a water potential of minus 0.7 megapascals.
结果是水势为负0.7兆帕。
Add the two components: minus 0.8 plus 0.3 gives minus 0.5 megapascals.
把两个分量相加：负0.8加0.3等于负0.5兆帕。
Water moves towards the lower, more negative potential.
水向更低、更负的水势移动。
A model cell has solute potential of minus 0.9 MPa and pressure potential of plus 0.2 MPa; its surroundings are at minus 0.4 MPa.
某模型细胞的溶质势为 −0.9 MPa，压力势为 +0.2 MPa；周围溶液为 −0.4 MPa。
Predict the initial net water movement, and the pressure potential at balance if the solute potential stays fixed.
预测最初的水分净移动方向，以及在溶质势保持不变时，平衡状态下的压力势。
The cell's total is minus 0.7 MPa, so water enters from the higher minus 0.4.
细胞的总水势为 −0.7 MPa，所以水从水势较高的 −0.4 MPa 一侧进入。
At balance, pressure potential is minus 0.4 minus minus 0.9, which is plus 0.5 MPa.
平衡时，压力势等于 −0.4 减去 −0.9，即 +0.5 MPa。
The fixed-solute assumption is a simplification.
溶质势保持不变是一种简化假设。
Pause and check yourself. Explain each point on screen in your own words, then change one number in the last example and say which assumption must still hold.
暂停一下，自我检查：用自己的话解释屏幕上的每个要点，再改动最后一个例子中的一个数字，说明哪个假设仍然必须成立。