Spring wood

...Therefore, when we look at the completed stem, we can see a clear difference between the areas where the cells formed during the period when the cambium was active were large and where there was a large amount of growth, and the areas where there was little growth and where there were many small cells. The former is called spring wood and the latter is called fall wood, and a pair of these indicates the amount of growth for one year, and since spring wood and fall wood are seen alternating in the wood, it is possible to confirm the amount of growth for each year. The circular patterns that appear on the cross section of wood like this are called annual rings. ...

*Some of the terminology that mentions "spring wood" is listed below.

Source | Heibonsha World Encyclopedia 2nd Edition | Information

…このため，でき上がった茎をみると，形成層のはたらきが活発であった時期に，つくられた細胞も大きく，生長量の大きい部分と，逆に生長量が小さくて小さな細胞が詰まっている部分の差がはっきりしている。前者を春材spring wood，後者を秋材fall woodと呼ぶが，これら1対で1年分の生長量が示され，材には春材と秋材が交互にみられるため，各年における生長量を確かめることができる。このように材の断面に環状に表れる模様を年輪という。…

※「spring wood」について言及している用語解説の一部を掲載しています。

出典｜株式会社平凡社世界大百科事典 第２版について | 情報