Botany

• Water is transported through the xylem (from roots to leaves) which is a specialized plant tissue.
• Root hair cells are tiny extensions of roots that reach far into the ground and have semi-permeable membranes that allow for uptake of water molecules through negative water potential in the leaves that cause the capillary reaction to replace water lost through transpiration in the leaves
• For the transport of water, the negative water tension in the leaves spreads through the xylem and down to the roots due to the cohesion of water molecules
• Water, during the capillary reaction, forms a cohesive column that does not pull away from cell walls and is instead pulled up as a transpiration stream
• Water is lost through the mesophyll cells into air spaces in veins and stomata through the leaves through transpiration
• Xylem sap is mostly water with low ion (K+, Cl-) concentrations
• Mass flow is where water travels through the cell walls (free spaces between cellulose, avoiding living content). It's also called the apoplast pathway and is the fastest mode of water transport
• Diffusion is where water travels through cytoplasms and openings. It's also called the symplast pathway and is resisted by organelles
• Osmosis is where water travels from vacuole to vacuole (pressure created when uptake of mineral ions from soil concentration). It's also called the transmembrane pathway and is usually only for individual cells
• Casparian strip is a waxy impermeable layer of cells to the centre of the root, preventing soil solution from diffusing through the apoplast pathway so that ions are selectively transported
• Pits (dead, hollow tubes) allow for water to enter and exit the xylem and is only present in mature plants
• Pits are hollow to minimize resistance to sap flow. When non-living, transport does not have energy and is passive, so needs to have reduced resistance for survival
• Hydrophobic lignin thicken = prevents breakage of xylem due to low pressure
• The Pith (inner) and cortex (outer) make up the ground tissue system
• The Pith (inner) and cortex (outer) make up the ground tissue system
• The generative nucleus in pollen divides into 2 haploid sperm cells to one, fertilize the cell, or create endosperm for nutrients. The tube cell grows down to the style to the overy in response to chemicals from synergids
• Between insect and wind pollinated plants, the following factors differ: Color of petals, scent + nectar, number of pollen grains, mass, weight + structure of pollen, location of anthers and stigma
• Fertilized eggs will turn into seed of fruit who's flesh = swollen overy
• Nectar glads around the base of the overy secretes nectar
• Sepals protect the flower
• Anthers create male pollen through meiosis and reveal them when mature
• To encourage diversification, cross pollination is promoted through; protandrous or protogynous to allow for female and male parts to mature at different times like in pecan trees
• To encourage diversification, cross pollination is promoted through; separation of female and male parts into separate flowers of the same plants
• To encourage diversification, cross pollination is promoted through dioecious plants where the male and female parts are on different plants entirely
• To encourage diversification, cross pollination is promoted through self-incompatibility mechanisms that prevent inbreeding by stopping the germination of pollen it recognizes as "self"- plants will same allele for incompatibility cannot pollinate each other
• Examples of plants that use seed dispersal by animals include takeaways like acorns or hitchhikers like cleavers
• Examples of plants that use seed dispersal through wind are parachutes like dandelions
• Examples of plants that use self-dispersal are pepperpots like poppies
• Germination needs temps btwn 20-30, water to flush inhibitory hormones, plant hormones to simulate mitosis and oxygen to produce energy and predigestion, washing, fire, pH, abrasion
• The seed's young shoot is the plumule, the young root is the radical, the bend in the shoot is the hypocotyl and the casing is made from cotyledons
• Water absorbed by micropyle washes inhibitory hormones and activates giberelin , the plant growth hormone, to simulate cell division and secrete enzymes like amalayse to synthesize lipids, carbs and proteins in endosperm to create sugars, amino acids and fatty acids that is transferred to embryo through cotyledons. Further hydrolysis turns starch into maltose, into glucose to be used for respiration
• Seed inhibition and germination is the mobilisation of stored food reserves
• Self-pollinated plants still cross over and are independently assorted during meiosis so offspring is similar but not genetically identical (like breeding within direct family in humans)
• Flowers and insects have a symbiotic or mutualistic relationship and they target specific insects to decrease visitation to other species of plants and increased fertilization rates (ex. Pea flowers n bees)
• When plants have both female + male parts they are complete, bisexual (hermaphroditic) and perfect
• When plants have either female / male parts they are incomplete, unisexual and imperfect
• Tube cell's intine is cellulose to help in maturation and exine is tough to protect passage
• the Pollen wall only surrounds one of the two nuceli that generates from the generative nucleus
• Micropyle allows entrance into ouvule
• The ovule has a micropylar end, close to the egg cell, and a chalazal end, on the opposite side with three antipodals. A central cell holds two nuclei to be turned into endosperm and 1 egg cell surrounded by two synergids waits at micropyle entrance to be fertilized