Small-cap stocks saw mixed trading Tuesday, as upgrades in the solar sector propelled some of the biggest gains.

Among the winners was Canadian Solar ( CSIQ - Get Report). Shares of this Markham, Canada, maker of solar module products rose 18% to $20.69 on an upgrade from Lazard Capital to buy from hold.

Also in the solar sector, Los Gatos, Calif.-based Akeena Solar ticked up 15% to $5.77 after Merriman Curhan Ford initiated coverage on the stock with a buy rating.

Meanwhile, Origin Agritech ( SEED) jumped 47.5% to $6.96. The Beijing-based producer of crop seeds on Monday updated its pipeline of genetically modified seeds, including phytase corn, which the company expects will be the first genetically modified corn product in China, and others. The company is also slated to report first-quarter earnings after the market close.

Phoenix, Ariz.'s Radyne surged 18% to $8.46. The company, which sells products and systems for operation of satellite, troposcatter, microwave and cable communication networks, announced its Xicom Technology business got a $5.8 million order for Tri-band and Ka-band power amplifiers. The order, which will ship in 2008, is part of the company's participation in the Air Force's GMT satellite communications program. Feltl & Co. upgraded the Radyne to buy.

On the losing side, San Jose chipmaker SiRF Technology dropped 28% to $4.94 after announcing that it would cut its workforce by 7%. The company also predicted first-quarter revenue between $60 million and $62 million, short of analysts' view of $74.2 million. Piper Jaffray lowered its rating of SiRF to sell from neutral.

Lasdon, S.C. maker of blast-protected vehicles Force Protection ( FRPT - Get Report) received a delisting notice from the Nasdaq stock market because it has yet to file its annual report on Form 10-K. Collins Stewart upgraded the stock to hold from sell, but shares nonetheless fell 1% to $2.

Lexington Realty Trust ( LXP - Get Report), a New York real estate investment trust, lost 5% to $15.15. Winthrop Realty Trust announced it had sold its entire $53 million stake in the company.

More broadly, the Russell 2000 was up 0.6% to 705.15, and the S&P SmallCap 600 added 0.5% to 373.84.