Answers

2015-10-03T07:01:17+05:30
Sclerenchyma tissue present in the covering of seeds makes it hard.The chemical called lignin is responsible for this hardness.This chemical is present on the the cell walls of sclerenchyma.
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2015-10-03T08:27:21+05:30
The seed coat develops from the material tissue, the integuments, originally surrounding the ovule. The seed coat in the mature seedcan be a paper-thin layer (e.g. peanut) or something more substantial (e.g. thick and hard in honey locust and coconut), or fleshy as in the sarcotesta of pomegranate.
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