Merriam-Webster's Collegiate Dictionary:
planimeter
planimetric
planimetrically
planing
planish
planisher
planisphere
planispheric
plank
planking
plankter
plankton
planktonic
planless
planlessly
planlessness
planner
planning
plano
plano-
plano-concave
plano-convex
planographic
planography
plant
plant city
plant food
plant hormone
plant kingdom
plant louse
plantable
plantagenet
plantain
plantain lily
plantar
plantation
planter
planter's punch
plantigrade
plantin
planting
plantlet
plantlike
plantocracy
plantsman
planula
plaque
plash
plasm
plasm-
plasma
plasma cell
plasma jet
plasma membrane
plasma torch
plasmagel
plasmagene
plasmalemma
plasmapheresis
plasmasol
plasmatic
plasmid
plasmin
plasminogen
plasmo-
plasmodesm
plasmodesma
plasmodium
plasmogamy
plasmolysis
plasmolytic
plasmolyze
plassey
plaster
plaster cast
plaster of paris
plaster saint
plasterboard
plastered
plasterer
plastering
plasterwork
plastery
plastic
plastic art
plastic foam
plastic money
plastic surgeon
plastic surgery
plastically
plasticene
plasticine
plasticity
plasticization
plasticize
plasticizer
plasticky
