3. Development of leaves

Question 1

How do dicot leaves develop?

Answer 1

Initiation at Shoot apical meristen→ Primordium formation → Cell division and expansion → Midrib and vein patterning → Mesophyll, epidermis, and stomata differentiation → Mature leaf structure

Question 2

what’s a buttress?

Answer 2

flared, ridge-like extensions of the tree’s lower trunk and roots that extend outward from the base of the tree, sometimes reaching several meters above the ground.

Question 3

What is intercalary growth? How does it occur in leaves?

Answer 3

-occurs at the bases of leaves or between nodes in monocotyledonous plants (monocots) like grasses and certain types of bamboo. This is in contrast to apical growth
-When environmental conditions are favorable, such as after rainfall or increased sunlight, intercalary meristems become active and start dividing rapidly.

Question 4

Development of monocot leaves

Answer 4

Initiation at SAM → Leaf primordium formation → Sheath and blade differentiation → Cell division and intercalary growth → Tissue differentiation (epidermis, mesophyll, vascular tissue) → Stomata formation → Mature leaf structure.

Question 5

Differences in sun/shade leaves

Answer 5

Sun leaves: high light, thicker, smaller, thicker cuticle, photosynesis in bright light, more pronounced veins, higher stomatal density
Shade leaves: low light, thinner, larger, thinner cuticle, lower stomatal density, photosynthesis in dim light, less pronounced vein structure

Question 6

Leaf abscission – what controls this and what happens?

Answer 6

-the process by which leaves detach from a plant, usually at the base of the leaf petiole. This process is a natural part of a plant’s life cycle and can occur in response to various environmental and internal signals
-controlled by hormonal signals (especially auxin and ethylene), environmental factors, and developmental cues
-deciduous plants, which shed their leaves seasonally.

Question 7

Fall color of leaves – how does this occur?

Answer 7

-As daylight hours shorten and temperatures drop in autumn, chlorophyll production slows down and eventually ceases.
-As chlorophyll breaks down, its green color fades, revealing other pigments that were previously masked.
-Yellow and orange pigments (carotenoids) become visible as chlorophyll diminishes.
-In response to environmental conditions, anthocyanins may be synthesized, adding red and purple hues to the leaves

Question 8

What affects leaf color?

Answer 8

environmental conditions, seasonal changes, plant health, and genetic factors

Question 9

What is a cladophyll?

Answer 9

-specialized type of stem that resembles a leaf in appearance and function
-They are adapted for photosynthesis and can be particularly useful in environments where traditional leaves might be disadvantageous.

Question 10

Examples of modified leaves?

Answer 10

-Tendrils
-Spines(looks like thin thorns)
-Bulbs
-Succulent
-Scale