test
node1
PECO:0007191
abiotic plant
exposure
node2
PECO:0007316
physical plant
exposure
node1->node2
node5
PECO:0007151
radiation exposure
node2->node5
node3
PECO:0007359
plant experimental
condition
node4
PECO:0001001
plant exposure
node3->node4
node4->node1
node6
BFO:0000003
occurrent
node6->node6
node8
BFO:0000015
process
node6->node8
node7
RO:0002310
exposure event or
process
node7->node5
node8->node7
node9
BFO:0000001
entity
node9->node6