negative gravitropism
Gravitropism (also known as geotropism) is a turning or growth movement by a plant or fungus in response to gravity. It is a general feature of all higher and many lower plants as well as other organisms. Wikipedia
posion ivy Vegetative propagation is the use of the part of a growing plant as either a cutting , graft or layer to root a new plant as opposed to germination from seed.
its a type of propigation either the leaf, root, or steam. how this works is they take a peice of the root leaf and or stem into the soil with a piece of the plant sticking out of the soil. what happens is an the plant grows from these they will star growing roots and root hairs(which absorbs water and nutrients)
cross-pollination
Sweet pea or Lathyrus is an annual plant
It is a tropism, specifically phototropism.
Stimulus is any kind of change in substances or in happenings, occurs in the surrounding of a living thing that bring about any kind of response from it.Tropism is the way by which plants respond to the stimuli. These kind of plant responses are either MOVEMENTS OR GROWTH of plat parts in particular directions.For Eg:-1. Leaves of 'touch me not plant' folds its leaves on our touch.2. plant roots grows towards the direction water availability.
Geotropism
Impossible to say. However, photosynthetic bacteria were around long before plants.
Gravitropism (also known as geotropism) is a turning or growth movement by a plant or fungus in response to gravity. It is a general feature of all higher and many lower plants as well as other organisms. Wikipedia
use a fast growing plant - some kind of seasonal plant that will give you fast results. an idea would be to use something like a petunia plant (an example of a flowering plant) and leafy green (foliage) plant - such as a lettuce plant - and see what changes if any are exhibited by both types of plant
Iris grows towards the light. That is phototropism.
positive gravitropism
mimosa pudica is a thigmotropism as it responds to touch :)
It depends on what kind of plant it is and it depends on what nutrition the plant gets. When its time for the plant to die it stops growing and starts dying.
Platyhelminthes exhibit bilateral symmetry, meaning they can be divided into two equal halves along a single plane. This symmetry type allows for better movement and coordination in these flatworms.
The silk is not growing, it's not a plant. This is a fiber, which can be woven in textiles. This kind of fiber is obtained from cocoons made by different larvaes.