Failure to build a controversial new power line could kill Scotland's renewable energy plans "stone dead", green businesses have warned.
The power line plans have brought local opposition
Opponents of the line said the larger pylons would ruin the landscape.
But industry forum Scottish Renewables said the 137-mile Beauly to Denny upgrade was necessary for the future growth of green energy production.
Scottish and Southern Energy has lodged a planning application for the new electricity transmission line.
It said that the current 132 kilovolt (kV) line would not be sufficient to feed power from the growing number of wind and hydro energy sites in the Highlands and islands to the National Grid.
The 400kV upgrade plan consists of 600 electricity pylons between Beauly in the Highlands and Denny, near Falkirk, running through the Cairngorms National Park and within sight of the Wallace Monument in Stirling.
The larger pylons would reach up to 65m high, although there would be 200 fewer than at present.
Outdoor groups and local protesters have called for the transmission line to be buried underground, but SSE claimed the cost implications would be too high.
And Maf Smith, chief executive of Scottish Renewables, said that if work on the power line did not go ahead Scotland's renewable energy industry would be "strangled at birth".
He said: "We believe that Scottish and Southern Energy has put forward a robust proposal that minimises impact to an acceptable level and is a vital improvement on the existing line it will replace.
"This upgrade to the power infrastructure is as fundamental to the economy as our road or rail infrastructure and future investment in renewables is dependent on this outcome."
Peter Pearson, secretary of Stirling Before Pylons, said: "There still isn't an overall energy strategy for Scotland.
"SSE haven't carried out a strategic environmental assessment which is required under European legislation, and which is currently going through the Scottish Parliament, to justify infrastructure proposals like this.
"Without a national strategy we don't think this line is justified."
Another protester, Caroline Paterson, said: "There is nothing green or sustainable about an increased number of children with leukaemia.
"The SSE's Dr Keith MacLean said health had not been a consideration in the routing of this line."
Independent MSP Brian Monteith, who has protested against the pylons, said: "Maf Smith clearly does not have a house under a pylon or children playing next to one.
"There is clear and unequivocal evidence that pylons are a danger to health and if this grid is to go ahead, all we are asking is that it should be put underground."
Scottish Renewables represents 160 green businesses and organisations.
The plans for the power line, being considered by the Scottish Executive, are out for public consultation until 12 December.