Plant growth & Differentiation Flashcards
(26 cards)
Growth
the prices of increasing in size
Differentiation
the process of cell specialization to allow for specific(xylem cells instead of ground cells)
Types of growth
- Apical meristems
- Lateral meristems
Apical meristems
- plant tissue composed of actively dividing cells; repsonsibke for primary growth and located at the tip of the roots and shoots of a plant
- increases height of plant
Lateral meristems
plant tissue consisting of actively dividing cells that produce secondary growth(increase width of plants)
Primary growth
-increased length of plant shoot or root
-cells divide by mitosis
-increased number of cells
-cells elongate then differentiate
-differentiation depends on location of meristem - shoot becomes stems, leaves, reproductive organs
Secondary growth
-only happens in woody species after first year
-secondary tissues produced
-ex vascular cambium, cork cambium
Environmental factors affecting plant growth and differentiation
-Light
-Nutrients
-Temp
-Soil
Light affecting plant growth
-any environment, the wavelength of light (light quality) that reach a plant will vary (differnt wavelengths at high noon vs evening)
-intensity of light and length of day also varies
-plant detects changes in light conditions using photoreceptors(detect light)
Photoreceptors
detect changes in light and this signals to the plant to change its growth or development(germination, leaf dropping)
Photoperiodism
plants response to changes in day length;
-Short day plants flower when the days are short(tulips)
-Long day plants fowler when there are 12h+ of day light(spinach)
-Day neutral plants aren’t affected by day length(roses, tomatoes)
Nutrients affecting plant growth
-Plants make carbs, fats, and protiens from inorganic substances called macronutrients and micronutrients
-macronutrients: plant nutrients needed in large amounts such as N, P, K
-Deficiencies of macronutrients leads to symptoms(nitrogen of magnesium deficiency can lead to chlorosis)
-micronutrients: plant nutrients needed in small quantities such as B, Cl, Cu, Fe, Mn, molybdenum, Ni, Zn. These are needed for chlorophyll, synthesis, cell division, and enzyme production
Temperature affecting plant growth
-Plants have optimal temp. range for cellular processes
-Temperature controls the opening and closing of stomata which helps control of transportation
-Timing of seed germination and flowering is affected by temperature
-Climate change is also having an effect. Every 1 degree can cause flowering to occur 5 days earlier. This can trick plants to flower before pollinators are available. If other plants are now flowering it can increase competition for pollinators
Soil affecting plant growth
- 3 important roles:
1. provides medium for roots to anchor;
2. it retains water/nutrients;
3. provides roots with air. - soil that has too much sand can lose water quickly, clay holds onto too much water and doesn’t have many air spaced which can cause plants to drown
-Soil must have humus: organic matter made up of decomposed organisms. Good for plants because it contains nitrogen
Plant growth regulators
-Chemicals that allow plants to modify their growth and differentiation
-Signal plant cells to undergo particular changes(elongate to bend one direction)
-Tropism
-Phototropism
-Gravitropism
-Thigmotropism
Tropism
a directional change in growth or movement in response to a stimulus. Plant will move to or away from the direction of the stimulus and this is hormone mediated
Phototropism
a change in direction of a growing plant in response to light. Occurs due to factor released from the top of the plant. This allows for increased light exposure
Gravitropism
a change in growth pattern in response to gravity( roots frown down, shoot grows up)
Thigmotropism
a directional change in growth pattern in response to contact(vines wrap around the other trees)
Nastic movements
-non directional movements which are independent of the direction of the stimulus
-Temporary and may take only a few seconds to occur
-Due to tugor pressure(water pressure inside plant) changes
-Plant will regain its original shape
various plant growth regulators
-Auxins
-Gibberellins
-Cytokinins
-Ethylene
-Abscisic acid(ABA)
Auxins
-Promotes cell division and elongation
-The cells in the shade have more auxin than those in the light which causes them to elongate and plant bends towards light
Gibberellins
-Promote cell division, cell elongation and seed germination
-Used commercially to promote seed germination stimulates flowering and fruit production
Cytokinins
-Prvent plant aging by inhibiting protien breakdown and stimulating
-Inhibits ethylene
