With reference to the use of Permanganate above, it is adding stain sure but it is also an oxidising agent and is acting on the fibre bundles in the grain and making them more visible, you can also use a dilute solution of Potassium Dichromate or Chromate which has a similar but less darkening effect. They (chromates)are especially effective on wood that has no,or very little grain figuring, it will selectively darken the bundles and make the grain more prominent, itdoes howeverr raise the grain becaaause it is waterbased so may need light rubbing down after it has dried.( I have used it to add some grain figuring effects to ash, which can be very featureless otherwise)
The method I used was to make a solution of Di or Chromate (1 g in 100 cm3 water) and apply lightly with a paper towel in the direction of the grain, leave for a few moments then mop off to dryness, reapply until the desired effect is achieved. rub down with 400grit emery just to restore grain, As the stain only penetrates a short distance into the wood, easy with the sanding.