Course 01 · Checkpoint 2 of 3 · Resources and transport

Checkpoint 2: Resources and transport

Photosynthesis, respiration, and the movement of water, sugars, and minerals, applied to realistic situations and care decisions.

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Before you start

8 questions, each worth one point. Some ask for one answer; others ask you to select a stated number of answers.
For questions with several answers, each correct choice earns an equal share of the point.
Pass with 80%: at least 7 of 8 points.
Untimed and open book. Revisit any lesson while you work.
After you submit, you will see every correct answer with an explanation. Retake it as often as you like.

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Question 1 of 8Instructional example: to thicken its trunk, the nursery juniper was planted in a sunny garden bed and allowed to grow freely for three seasons. When it was lifted, its trunk had added many layers of new wood and was considerably thicker.Where did most of the dry mass of that new wood come from?
The water its roots drew up, which its foliage turned into wood using the energy of lightCarbon dioxide from the air, which its foliage built into sugars using the energy of lightThe sunlight that fell on its foliage, which the tree turned into the solid substance of woodThe garden soil, whose minerals and organic matter its roots absorbed and built into wood
Question 2 of 8Instructional example: the ficus spends the warm months outdoors in full sun. Two summers ago it was repotted into a free-draining mix of mostly inert grit, such as pumice and lava rock, which holds few nutrients of its own, and it has not been fed since. For several weeks this summer its leaves have been evenly paler green than in past years, veins included and older leaves as much as new ones, and its new shoots are short. Checks show a root zone that is moist but not soaked, a pot that drains freely, firm roots with pale, growing tips at the drainage holes, and no pests on its leaves or shoots.What is the best next step?
Feed it at the label rate, since its mix holds few nutrients and it has gone two summers without feedingWater it more often, so that its roots can draw more of the nutrients already in the mix into the treeFeed it at twice the label rate for a few weeks, so that it can quickly make up for what it has missedKeep it unfed, since short, pale growth keeps a bonsai small without doing it any lasting harmWait another season before feeding, since paleness has many causes and feeding is rarely the answer
Question 3 of 8Instructional example: it is noon on a bright summer day. The trident maple's sunlit leaves are taking in carbon dioxide and giving off oxygen. Deep in its free-draining pot, its fine root tips are growing and taking up mineral nutrients.Which statement about respiration in this tree right now is accurate?
The root tips are respiring, with oxygen that the sunlit leaves release and send down through the trunkOnly the roots and other parts out of the light are respiring; the leaves will start once the light fadesEvery living cell is respiring, from leaves to root tips, though in the sunlit leaves photosynthesis hides itNothing is respiring yet; by day the tree runs on photosynthesis, and respiration takes over at night
Question 4 of 8Instructional example: on a bright morning, the trident maple is in full leaf, and its root zone is moist after a thorough watering.Which sequence correctly traces the route taken by most of the water the tree absorbs?
Water films around substrate particles → root hairs and young roots → phloem in the inner bark → leaf veins → evaporation inside the leaf → stomataWater films around substrate particles → root hairs and young roots → xylem in the wood → leaf veins → stomata → evaporation on the leaf surfaceWater films around substrate particles → root hairs and young roots → xylem in the wood → leaf veins → evaporation inside the leaf → stomataWater films around substrate particles → root hairs and young roots → xylem in the wood → leaf veins → phloem back down to the roots
Question 5 of 8Instructional example: the ficus spends its summers outdoors on an open balcony. Ten days ago it was repotted into fresh, coarse, free-draining substrate, and a substantial share of its roots was trimmed away. This afternoon is hot, bright, and gusty; the soft tips of its new shoots have bent over, and its younger leaves hang limp. A wooden skewer pushed deep into the root zone comes out dry, the substrate at the drainage holes is dry to the touch, and the pot feels light when lifted.What is the best immediate response?
Move it to a bright spot out of the wind, since shelter, not more water, is what a repotted tree needsTrim off about half of its leaves, so that the reduced roots have less foliage to keep suppliedGive it only a small splash of water, since freshly trimmed roots can rot if the pot is soaked throughWater the root zone thoroughly now, until it drains, since its reduced roots sit in dry substrate
Question 6 of 8Instructional example: in early summer, a few weeks after the trident maple's spring flush, a hailstorm shredded most of its leaves. Since then, buds along its branches have begun opening into small replacement shoots and leaves. Before the storm, its owner had planned to cut its branches back hard next week to refine its shape.What is the best decision about the planned pruning?
Go ahead next week, since its new shoots opening so soon show that it has plenty of reserves to sparePostpone it, keep the new leaves in good light, and judge the tree's recovery by the growth that followsGo ahead next week, and give it extra fertilizer so it has the energy to replace what it losesPostpone it, and move the tree into shade to rest until its new leaves have finished opening
Question 7 of 8Instructional example: in early summer, while the trident maple is growing strongly on its outdoor bench, a squirrel strips a complete ring of bark from one of its leafy branches, down to the wood. All of that branch's leaves grow beyond the ring, the wood beneath is untouched, and the wound is left uncovered.The diagram shows the branch just after the bark was stripped, joined to the trunk at the left; proportions are simplified. Which two of these would you expect over the following weeks? Select two.0 of 2 selected
The roots get no sugar from this branch's leaves, though the tree's other branches still supply themThe bark edge at C swells, as sugar heading from the leaves toward the trunk and roots collects thereThe leaves beyond the ring wilt within days, because the bare wood at A no longer carries their waterThe roots get no sugar from any of the tree's leaves now, so the whole tree begins to declineThe bark edge at B swells, as water rising from the roots collects there on its way through the wood
Question 8 of 8Instructional example: an azalea bonsai, a shrub that needs a more acidic root zone than most trees, has grown well for several years in a bright spot outdoors. It is watered from a hard tap-water supply that leaves white lime spots on the watering can. This season its newest leaves have come out yellow between their veins, while the veins themselves and the older leaves stay green. Checks show a root zone that is moist but not soaked, a pot that drains freely, and firm roots with pale tips at the drainage holes. It has been fed at the label rate, and its owner plans to feed it twice as often.What is the best next step?
Move it into deeper shade, since strong light is bleaching the color from its newest leavesFeed it twice as often as planned, so that more iron and nitrogen reach its newest leavesWater it more often, since leaves that yellow between their veins show the roots are short of waterFind out whether its root zone has become too alkaline, which can lock away iron that is present

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