Roots: The League of Nature is a pun on the League of Nations. Alex Marlowe is based on philanthropist rock stars, particularly Sting, Bono and Bob Geldof (although having gone into politics we could also include Australian Green/Labor MP Peter Garrett, formerly of Midnight Oil). Marlowe namechecks All Creatures Great and Small (probably the song rather than the TV series). The Hothouse is likened to The Eden Project. Lucie calls the Doctor "Mister Titchmarsh" (after TV gardener Alan Titchmarsh for those outside the UK bubble.)
Intertextuality: The Doctor invokes his Ninth incarnation with a different kind of fruit from The Doctor Dances ("lemons are good")
Dialogue Triumphs: "Nothing's ever the same, Lucie Miller. Everything's always brand new, that's what keeps me going."
Dialogue Disasters: "You mentalist! You... enviro-mentalist!"
"Time for your companion to 'go green'..."
Double Entendres: Lucie's suspicious knowledge of lamps "You know, for growing stuff in your attic"
Technobabble: Marlow is experimenting with the Krynoids' chemico-cellular physiology.
Goofs: It is implied that Marlow has been onto Lucie's subterfuge for a while, so if he was so keen to meet and kidnap the Doctor, why not just agree to meet him on his visit, rather than allow him to break in later and then do it?
Marlow says nobody knows where the Doctor and Miss Bright are - but presumably their driver knew where they were going?
Continuity: Alex Marlow was formerly the lead singer of 'world-famous' rock band The Experts and until recently worked to save endangered species. He is now head of the League of Nature, a political pressure group boasting eighty million paid-up members campaigning on environmental issues, the greenhouse effect in particular. Among their policies is a ban on private capital. The League seem to be greatly at odds with the World Ecological Bureau (see: Links), to the extent of industrial espionage - the implication being that the LON see the WEB as an 'establishment' organisation. His project, The Hothouse comprises five biodomes in a locked-down compound, containing many species extinct in the wild. Also housed there are Krynoid pods cultivated from cuttings recovered during the 'Chase' episode (i.e. the previous Krynoid experiment by Harrison Chase).
The World Ecological Bureau continue to maintain links with UNIT and via them have a means of communicating with the Doctor via the Space-Time Telegraph. Its local office is based in White City, where the TARDIS is stationed for this story. It would appear that the notes of Sir Colin Thackeray following the Chase Incident put 'them' (and via their spies, the league of nature) onto the existence and means of contacting the Doctor. In the intervening years between the earlier incident and the present day Sir Colin has died.
The St Petersburg Bioprotection Treaty authorises the WEB to inspect any facility used for agricultural research.
The Krynoids here are experimental breeds featuring (although not collectively) accelerated germination (i.e. transformation of the animal host) and varying degrees of control over the host organism. They hatch from pods as in the earlier story, yet are also able to be cultivated from cuttings and are said to reproduce by spores also. For the first time we 'hear' inside the mind of a Krynoid subject and the enhanced faunal consciousness emerging, described by Miss bright as 'the forest singing' and sounding, to intents and purposes, like a rainforest, complete with bird and insect sounds.
The Doctor seems to be still partly amnesiac following his recent recovery on Orbis - he has forgotten how to drive a car, for example. His sonic screwdriver isn't yet up to the job of cutting a steel mesh fence, although he admits that he intends to address this in time. He hasn't heard of Alex Marlowe (or has forgotten who he is).
Location: Southern England, early 21st century (pre-2060).
Future History: Earth's environment is said to be close to collapse due to the greenhouse effect. News reports mention twenty weeks of drought (or twenty-two without rain) in the United Kingdom with reservoir levels down to five percent capacity. A 'tragedy' in Dhakar and (possibly linked) a refugee crisis which hit the Eurozone in the previous year saw a refugee population in the millions displaced from North Africa and the Black Sea states, forcing a desperate Eurozone to close its borders. Rationing is in effect and there have been riots in Paris and Madrid. Extinctions in the wild within the last five years include the cheetah and white rhino. Half of the Amazon basin is now a dustbowl.
Links: The Seeds of Doom (W.E.B, Sir Colin Thackeray, The 'Chase Incident'), Terror of the Zygons (The Space-Time Telegraph), Orbis. By 2060 the Amazon 'dust bowl' will be complete (Loups-Garoux). This story concludes with no solution found for the coming global environmental collapse, and leads to the developing Eightfold Truths story (The Eight Truths).
The Bottom Line: "Death by salad!"
Surely the easiest story to write. Krynoids, plus fanatical sympathiser, plus the threat of imminent global catastrophe due to both previous factors. As such, Hothouse is an unremarkable story, although Nigel Planer's Marlowe is almost as fun as Harrison Chase (but not nearly as camp),and the body horror is reliably attended to.