Poles today began paying up to 300 percent more for bread and grain, the biggest price increases for these heavily subsidized staples since the Communists took control of the country after World War II.

Traditionally in Poland, price increases have served as a trigger for industrial unrest, including the wave of strikes that led to the momentous agreements between government and workers last year.

This time, the population appears to have accepted the increases, and there was little public reaction reported. Price raises for other foodstuffs, including meat, are planned over the next few months.

One reason for the moderate response lies in the fact that the present increases, which coincided with the first anniversary today of the Gdansk agreement which permitted independent trade unions for the first time in a communist state, were preceded by long negotiations between the Communist authorities and the independent Solidarity trade union federation.

Another is that Poles will receive extra allowances to compensate for the higher cost of living.

Following widespread protests over food shortages earlier this month, Solidarity's attention has now switched to winning greater access to the mass media and a battle over the extent of economic reform. Today, as consumers began paying more for bread, talks resumed between government and Solidarity representatives over television coverage of the union's first national congress, which begins Saturday.

The new prices mean that a regular 1 3/4-pound white loaf now costs 16 zloties (about 50 ) rather than the 20 it cost yesterday -- an increase of 138 percent. Flour has gone up 243 percent to 32 a pound, spaghetti 300 percent to 92 a pound and rice 250 percent to 38 a pound.

In return, individual Poles are to receive between $5 and $6.25 a month in compensation, depending on their income.

The aim is to restructure prices so that it will no longer be economic for private farmers to feed bread and other processed food products to their animals. Under the previous price system, huge amounts of bread were wasted since it was cheaper than grain.

Over the last two months, bread shortages have become increasingly common and grain products have had to be rationed.

A spokesman for the government's price commission said that today's increase in the price of bread was the first since 1963, when the size of the loaf was cut by 20 percent. Since then, however, there have been several smaller "hidden" increases accomplished by substituting one type of bread for another.

Before 1963, the bread price had remained the same for over 15 years: four zloties (about 12 ) a loaf.

For years, Soviet Bloc ideologists liked to boast that constant prices were proof of the superiority of their system over the West's. Inflation was described as a capitalist disease that could not exist in a communist country.

The result of this ideological commitment to cheap food, however, was an ever-increasing disparity between prices and costs. The economic system was thrown into disorder and price subsidies grew to account for up to half the national budget. Shortages became more widespread.

Polish workers, meanwhile, took the regime's slogans at face value and reacted sharply against the theoretically impossible price increases when they were finally introduced. In December 1970, a series of increases had to be rescinded after strikes and riots brought about the fall of Wladyslaw Gomulka, then leader of Poland's Communist Party.

It is still too early to tell whether today's price increases will be sufficient to reduce the huge lines outside food shops. First reports suggested that they were as long as ever.

Meanwhile another warning that the country was reaching a critical point came from the prime minister, Gen. Wojciech Jaruzelski. In an address to military school graduates, he said soldiers had the moral right to say: "Enough of anarchy."

He said Solidarity would have to decide at its congress whether to engage in constructive cooperation with the authorities or confrontation and the answer would determine Poland's future.