参天大树之所以高大,是因为它的茎极其发达的缘故,一般乔木类植物都是这种茎。我们把这种背地面而生的茎叫做直立茎。然而,植物并不都是直立、高大的,有些植物的茎本身细长而柔软,不能直立,只能缠绕在其他物体上向上生长,这种茎叫做缠绕茎。如牵牛花、金银花的茎。另外,还有一些植物如黄瓜、葡萄等,它们的茎虽然也是细长柔软的,但它们既不能直立生长, The reason why towering tall trees because of its extremely developed stem reason, the general arbor are this stem. We call this stalked stem the upright stem. However, not all plants are erect, tall, some stems themselves slender and soft, can not stand up, can only be wound on other objects upward growth, this kind of stem is called winding stems. Such as morning glory, honeysuckle stems. In addition, there are some plants such as cucumbers, grapes, etc., although their stems are also slender and soft, but they can neither stand upright,