What is photosynthesis?
See how leaves use light to make sugars and other organic materials.
Topic B
How Plants Stay Alive
Start with light, water, and air, then connect photosynthesis, water movement, respiration, and plant responses to everyday observations.
A plant leaning toward a windowLeaves receiving lightWater changing in a pot
Reading Path
How does a plant get energy and materials?
Each topic gives a simple route first, then connects to individual articles.
How does water move from roots to leaves?
Connect roots, stems, and leaves as one transport system.
Why do plants bend toward light?
Use a window-side plant to understand phototropism.
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English Articles
What is photosynthesis? Photosynthesis is the process in which plants use light energy to turn water and carbon dioxide into sugars and other organic materials, releasing oxygen along the way.
Why do plants need sunlight? Plants need usable light—not sunlight as food—to power photosynthesis and support growth. Light also helps plants respond to direction, day length, and seasons.
What is chlorophyll? Chlorophyll is a light-absorbing pigment, not plant food. Learn how it works in chloroplasts, why many leaves look green, and what yellowing or variegation can suggest.
What is transpiration in plants? Learn what transpiration is, how water moves from roots through xylem and leaves into the air, and why heat, dry air, and moving air can increase water loss.
How Does Water Move from Roots to Leaves? Water enters through roots, travels in xylem, and reaches leaves through a connected pathway. Learn how transpiration pull, water potential, and root-zone conditions shape plant water transport.
Do plants breathe? Plants do not breathe with lungs, but their cells do respire. Learn how plant respiration uses sugars and oxygen, why roots need air, and how it differs from photosynthesis.
Why do roots need air? Roots need oxygen for cellular respiration. Learn how water and air share pore spaces in potting mix, and why long-lasting saturation can slow root function.
Why do plants bend toward light? Plants bend toward light because new growth responds to directional light. Learn how phototropism, auxin, shaded-side elongation, and window growing fit together.
What Is Phototropism? Phototropism is a type of tropism: a directional plant growth response to light. Learn positive phototropism, negative phototropism, why plants have it, and how it differs from photosynthesis and leggy growth.
How do plants sense day and night? Plants sense light without eyes. Learn how photoreceptors, circadian rhythms, and photoperiodism help plants track day, night, seasons, and the possible effects of light at night.
What Is Photoperiod in Plants? Photoperiod is the length of light and darkness a plant experiences in a daily cycle. It is not light intensity or photosynthesis; it is a timing signal plants can use to track seasons and development.
Why Do Plants Flower? Plants flower when they shift from leaf, stem, and root growth toward reproduction. Learn how maturity, day length, cool periods, and plant type affect flowering.
What Is Flower Bud Differentiation? In gardening, flower bud differentiation often refers to the continuous development from flower-bud initiation through the formation of flowers and floral parts inside a bud. Learn how it relates to a visible bud and how maturity, seasonal cues, and plant type shape flowering development.
What Are Plant Hormones? How Plant Signals Shape Growth Plant hormones are chemical signals made in very small amounts that help regulate growth, development, and responses to the environment. Learn how auxin, cytokinin, gibberellin, ABA, and ethylene work together.
What Is Auxin? How Plants Use Location and Concentration to Regulate Growth Auxin is a class of plant hormones that helps shape growth according to where it is, how much is present, and which tissue receives it. Learn how it relates to phototropism, gravitropism, apical dominance, root formation, and cutting propagation.
Why Do Plants Go Dormant? Plant dormancy is a pause in visible growth, not death. Learn why buds, seeds, bulbs, and crowns may pause growth—and how dormancy differs from slow winter growth and vernalization.
What Is Vernalization? Vernalization is how sustained cold helps some plants gain the ability to flower or flower sooner. Learn how it differs from photoperiod, cold acclimation, dormancy, and cold stratification.
If plants make their own sugars, why do they still need mineral nutrients? Plants make sugars through photosynthesis but still need mineral nutrients. Learn how dissolved ions move from roots through xylem, and why N-P-K is only part of plant nutrition.
What Are N, P, and K? Why Plants Need These Nutrients What do N, P, and K do for plants? Learn their roles, the ions roots take up, how nutrients move through the plant, and why one symptom is not a diagnosis.
How Do Plants Grow Taller? From the Shoot Tip to Cell Elongation Learn how plants grow taller through cell division, cell elongation, and internode growth—and why height growth is different from thickening, phototropism, and leggy growth.
How Do Plants Repair Wounds? Plants often respond to injury by sealing wounds, compartmentalizing damaged tissue, and activating defense signals. Some tissues can regenerate, but closure is not full restoration.
What Does Water Do in Plants? Water helps plants stay firm, move minerals, make sugars through photosynthesis, and cool leaves through transpiration. Learn why plant water is more than just moisture.
How do plants transport nutrients? Learn how plants move water and mineral nutrients through xylem, distribute sugars through phloem, and shift source and sink roles as leaves and storage organs develop.
How Do Plants Sense Gravity? Why Roots Grow Down, Stems Grow Up, and What Gravitropism Means Roots often grow downward and shoots often grow upward because growing plant tissues respond to gravity. Learn gravitropism, statoliths, auxin patterns, and why roots and shoots bend in different directions.
How Are C3, C4, and CAM Plants Different? C3, C4, and CAM plants share photosynthesis but handle CO₂ differently. Compare spatial and temporal separation, stomata, photorespiration, heat, and water-use efficiency.
Why Do Some Plants Grow More Slowly Under Stress? Drought, low light, unsuitable temperatures, salinity, and low root-zone oxygen can slow cell expansion and new growth. Learn how water, stomata, photosynthesis, and stress signals interact without treating slow growth as a diagnosis.
When Do Plants Close Their Stomata? When do plants close their stomata? Learn how light, drought, heat, dry air, high VPD, leaf CO₂, and CAM photosynthesis shape stomatal opening and water loss.
What Happens to Plants When They Lack Water? When plants face water stress, stomatal conductance and growth may decline before visible wilting. Learn how guard cells, ABA, turgor, transpiration, and prolonged water deficit fit together.
What Are Root Nodules? What Do the Small Bumps on Legume Roots Do? Root nodules are structures formed through cooperation between legume roots and rhizobia. Learn how symbiotic nitrogen fixation works and what root nodules can—and cannot—tell you.
How Do Plants Sense Touch? Mimosa, Tendrils, and Plant Movement Plants can detect mechanical stimuli without an animal-like nervous system. Learn how mechanotransduction links force with Mimosa leaf closure, tendril coiling, and slower changes in plant form.
What Is a Plant Circadian Rhythm? How Light and Darkness Set the Clock Plants have internal circadian rhythms that run on a roughly 24-hour cycle. Learn how light and darkness entrain the clock and shape leaf movement, stomata, growth, and seasonal responses.
What Is Ethylene? How Plants Use a Gaseous Hormone in Ripening, Leaf Fall, and Stress Responses Ethylene is a gaseous plant hormone involved in fruit ripening, leaf senescence and abscission, and responses to wounding or flooding. Learn how diffusion, receptors, ACC, and hormone crosstalk shape its effects.