plant disease and defence Flashcards
(8 cards)
what are the four plant diseases that we need to know?
magnesium
rose black spot
tobacco mosaic virus
nitrate deficiency
what is magnesium deficiency in plants?
it caused by low levels of magnesium ions in the soil
the plant can not make chlorophyll so leaves become yellow (this yellowing of leaves through lack of magnesium is called chlorosis)
growth slows down as the plant needs magnesium to photosynythesize
its non communicable disease
replace mssing mineral ions with fertilizers
what is rose black spot?
its caused by a fungus
symptoms include purple or black spots, leaves falling early and the leaf may turn yellow around the spots
the black spot fungus produces spores which are spread by the wind and rain. It can also be spread on hands,clothing or tools
to control the spread you can collect and destroy in autmn,prune out all stem lesions in spring before leaves appear on or use fungicides
what are some physical barriers in plants?
cellulose walls-provide a barrier to infection
tough waxy cuticles on leaves
bark on trees-a layer of dead cells that can fall off
what is tobacco mosaic virus?
its a widespread plant pathogen
symptoms are a mosaic pattern of discoleration on the leaves as the virus destroys the cells or brown spots. It also affects the growth of the plant.
its spread by contact between diseased and non diseased plant materials or insects can act as vectors
there is no treatment but good field hygiene and growing TBR resistant strains of crops can help prevent it
what is a nitrate deficiency?
its caused of nitrate ions in the soil
causes protein growth to be limited and growth of plant to be stunted and wont produce a crop properly
nitrate ions are needed to convert sugars made in photosynthesis into proteins needed for growth in protein synthesis
replce missing nitrate ions with fetilizers
what are the chemical barriers in plants?
many plants produce antibacterial chemicals
poison production stops animals eating plants
what are the mechanical adaptations in plants?
thorns and hairs stop animals eating plants
leaves that droop or curl when touched to scare herbivores or dislodge insects
some plants mimic the appearance of unhealthy or poisonous plants to deter insects or herbivores
