45}{500}=\\htmlData{anchor=x_ratio}{0.09\\ \\mathrm{cm^3\\,g^{-1}}}"},{"latex":"Y=\\frac{96}{1200}=0.08\\ \\mathrm{cm^3\\,g^{-1}}"},{"latex":"Z=\\frac{60}{1200}=0.05\\ \\mathrm{cm^3\\,g^{-1}}"}],"highlights":[{"color":"green","style":"box","anchor":"x_ratio"}]},"order":2,"title":"Calculate each ratio","description":"Use the same division for every mix: water retained divided by dry mass."},{"type":"text","order":3,"title":"Choose the best mix","content":"Compare the four calculated values: mix $X$ retains the most water per gram of dry substrate, so choose **substrate mix X**.\n\nTogether with the calculations in the preceding step, this earns **M1**: you have calculated and compared water retention per gram, then identified the best mix.","highlights":[{"text":"which is most suitable for establishing young saplings in a drought-prone reforestation site during a dry, hot summer","location":"specification"}]},{"type":"text","order":4,"title":"Link it to survival","content":"In hot, dry weather, leaves lose water rapidly by **transpiration** (evaporation of water from the leaves). Mix $X$ retains the most water per gram, so the soil keeps a higher **water potential**. Water potential is a measure of water's tendency to move.\n\nThis maintains a continuous supply of water into the saplings to replace the water lost by transpiration. The cells are less likely to lose water and wilt (or become plasmolysed), so the saplings are more likely to survive. This explanation earns **A1**.","highlights":[{"text":"during a dry, hot summer.","location":"specification"}]}]}],"generatedAt":"2026-07-22T09:04:32.946Z","modelVersion":"gpt-5.6-terra+diagrams-1","explanationVersion":"v3"},"options":[]}],"options":[],"explanation":null,"firstAttemptFullMarks":null},{"id":"8cb2551c-5e5d-40b4-b9cb-3a042f0db5d2","revisionId":"6b81c744-fadf-47e2-adba-d4575e6dad9d","questionNumber":null,"questionType":"LA","specification":"Figure 1 shows a simplified diagram of a longitudinal section through a specialized xylem vessel.\n\n![Figure 1: Simplified diagram of a longitudinal section of a xylem vessel.](https://assets.mathsgenie.co.uk/aqa-qb/2da256cb-b83d-4c64-ba27-6d2863fe8038.png)","difficulty":4,"difficultyBand":"medium","totalMarks":4,"sourceTitle":null,"calculatorUse":null,"parts":[{"id":"c10c542c-cd6a-4797-9223-374420cb2e80","label":null,"content":"Describe two structural features of the xylem vessel shown in Figure 1 that adapt it for its function.","markscheme":"- **Helical/spiral lignin thickening**: strengthens the cell walls to prevent the vessel from collapsing under tension or negative pressure. B1\n- **Bordered pits / lateral pores**: allows the lateral movement of water between adjacent vessels or around blockages. B1\n- **No end walls / continuous hollow tube**: allows an uninterrupted, continuous column of water to rise with minimal resistance. B1\n- **No cytoplasm / absence of organelles**: provides a completely hollow lumen which minimizes resistance to the upward flow of water. B1","marks":4,"order":0,"markingRubric":null,"explanation":null,"options":[]}],"options":[],"explanation":null,"firstAttemptFullMarks":null},{"id":"95c0cd75-7e79-4971-aa62-b81fe2e4f572","revisionId":"394e766f-108f-411f-b558-16cdcdf6367f","questionNumber":null,"questionType":"LA","specification":"$41","difficulty":5,"difficultyBand":"medium","totalMarks":3,"sourceTitle":null,"calculatorUse":null,"parts":[{"id":"7424d3cd-43ac-4a19-82ec-aec8f09bd47d","label":null,"content":"Explain why switching on the fan caused an increase in the rate of water movement through the potometer.","markscheme":"- (Increased air flow) removes or sweeps away water vapour from immediately around the surface of the leaf B1\n- This maintains or increases a steep concentration gradient of water vapour between the air spaces inside the leaf and the surrounding atmosphere B1\n- This increases the rate of diffusion of water vapour out of the stomata (or evaporation from spongy mesophyll cells), drawing wa

Transport and transpiration in plants

Question 27

Transport and transpiration in plants Questions

Transport and transpiration in plants

Question 27

Transport and transpiration in plants Questions