Four California partnerships in the plant marketing business have admitted Securities and Exchange Commission charges that they failed to register with the commission and failed to keep investors up to date.

The companies, part of a network of 51 limited partnerships that have been sold to investors as tax shelters, are the targets of an ongoing SEC investigation into whether the companies violated antifraud provisions of federal securities laws and whether they continued to recirculate money from one entity to another in an operation similar to a pyramid scheme.

Involved in the investigation are four California firms, California Flowerland Ltd., California Flwerland '79, CF Partnership and California Flowerland Inc., and dozens of Florida partnerships. According to information filed in U.S. District Court here earlier this month, the network of partnerships may have raised "approximately $70 million in cash and notes . . . approximately 2,000 investors through the sale of interests in these partnerships in over 30 states."

As part of the settlement reached late Wednesday, a special agent was appointed to administer the business affairs of the partnerships while the investigation continues and the firms' affairs are sorted out.The court-appointed receiver is Robert A. Baker, who has stepped into the affairs of other troubled companies to help sort them out.

In a simultaneous court actions Wednesday the SEC asked for an injunction to prevent the four California firms from violating the SEC's registration provisions; the firms filed a separate complaint against the other limited partnerships, a supplier and others, alleging that the assets of the companies were so intermingled that it had been impossible to meet the SEC's registration requirements, and the SEC and the partnerships entered into a consent decree and settlement.

The settlement makes it clear that the investigation is continuing and that the settlement can be amended.

In a request earlier this month for a subpoena of accounting firm records of the various corporations, the SEC spelled out some suspicions about the operations of the firms, including whether investors have been misled by representations of the partnerships as tax loss investments.

"The commission is investigating whether millions of dollars of funds of the partnership may have been commingled and misappropriated and whether funds raised in the sale of interests in any one partnership may have been used to finance distributions to the limited partners of previously formed partnerships," according to court papers.

Island Foliage Inc., identified in the companies' complaint as a principal horticultural supplier, did not enter into the consent agreement.