Whole Plant Growth Flashcards
population growth
- more than 100 years of classical growth theory
- exponential
populations in this case means metabolically active cells, leaves, roots, and photosynthetic stems
relative growth rate
- an extractable parameter
- analogous to population growth
- not constant
- plant growth is not exponential
- helps us understand growth and its relationship to plant structure and physiology
from all the equations in this unit, how is mass measured?
- in dry mass
- also can include indices of size like leaf area, height, trunk diameter, and leaf number
why is RGR relative?
-considering growth increase that is relative to the plant size
absolute growth rate
- does not allow us to understand physiological drivers of changes in growth rates or compare behavior or performance across plants
- bigger plants always have inherently bigger absolute growth rates
- you would essentially always be measuring size
do juvenile plants have faster or slower growth than adults?
- faster
- they are tiny because they quickly increase their mass by orders of magnitude
LAR
- leaf area ratio
- leaf area / plant mass
- morphological index (structural)
- all of the leaves together versus the mass of the plant
- higher magnitude than ULR
- = specific leaf area x leaf mass fraction
ULR
- unit leaf rate
- mass accumulated per leaf area per time
- physiological index (metabolic)
- like net photosynthetic rate per leaf area, but integrated over time and is
diminished by respiration and any loss of tissue over time - critical part is how long a leaf lives
SLA
- specific leaf area
- leaf area / leaf mass
- factor contributing to high RGR
- commonly a plant functional rate because of its
relationship to RGR and photosynthetic rate and because changes in SLA are major mechanisms for acclimation and adaptation to environment - RGR is equally changed by SLA and LMF
LMF
- leaf mass fraction
- leaf mass / plant mass
- factor contributing to high RGR
- leaf
higher or lower SLA for thinner leaves
- SLA is higher for leaves that are thinner or less dense
what are the components of leaves with high SLA?
large surface area, efficient photosynthetic
apparatus, stomatal pore area, etc per leaf mass
SMF
stem mass fraction
RMF
- root mass fraction
- investment in roots is often a result of water or nutrient stress
longer lifespan
higher ULR because leaf mass is lost less frequently
- lower RGR because leaves are slowing down as they age
what happens to long lived leaves?
associated overall with a slower RGR because leaf lifespan is strongly negatively correlated with SLA
- thick, dense leaves last longer and are less vulnerable to
herbivores
plasticity
- changes in form and physiology when plants are grown in different conditions
- arise from interactions between genes an environment = changes in gene expression
adaption
- long term, evolutionary changes in plant form and physiology
- are purely genetic = heritable changes in standing genetic variance
what are the extent of the differences in plasticity?
depends on how long plants grow in a different environment and intrinsic difference in growth rates
irradiance plastic changes
- plastic changes for plants grown in shade
- increased SLA
- reduced RMF
- may compensate for the shade to some degree
higher nutrient supply plastic changes
- plastic changes for plants grown in higher nutrient supply
- increased SLA
- reduced RMF
higher water supply plastic changes
- plastic changes for plants grown in higher water supply
- increased SLA
- possibly reduced RMF
irradiance adapted changes
plants adapted to shade lower SLA and higher RMF
- This is because plants in chronic shade have low demand for energy and tolerance of other stresses
- lower SLA corresponds with a longer leaf lifespan (not enough light to make new leaves)
- higher RMF allows shade plants to compete for resources
higher absolute growth rate
lower RGR
the same applies for lower absolute growth rate = higher RGR
why do bigger things have bigger absolute growth rates?
- more cells
- lower RGR because respiration slows down as things age
