24 How to Build a Tree-High

How to Build a Tree FOCUS Question How does a tree get the matter it needs to grow?

如何种植树木焦点问题一棵树如何获得生长所需的物质?

Food for Trees Imagine looking up at the tallest tree in the world— a California redwood named Hyperion. Its massive trunk reaches for the sky. Its evergreen branches tower 116 meters (381 ft.) overhead. How did Hyperion get so enormous? In order to grow, trees need to produce food. They do this through the process of photosynthesis. During photosynthesis, plants harness energy from the Sun to convert water and carbon dioxide into glucose and oxygen. Glucose is a type of sugar that is food for trees. Trees utilize some of this sugar to grow, producing matter in the form of leaves, wood, bark, flowers, cones, or fruit. Trees also store some glucose to use later as energy.

树木的食物想象一下，抬头看着世界上最高的树——一棵名为亥伯龙的加州红杉。 它巨大的树干伸向天空。 它的常绿树枝高达116米(381英尺)。 土卫七是如何变得如此巨大的? 为了生长，树木需要生产食物。 它们通过光合作用来做到这一点。 在光合作用过程中，植物利用来自太阳的能量将水和二氧化碳转化为葡萄糖和氧气。 葡萄糖是一种糖，是树木的食物。 树木利用这些糖的一部分来生长，以叶子、木头、树皮、花、球果或水果的形式产生物质。 树木也会储存一些葡萄糖，以供日后作为能量使用。

Photosynthesis occurs inside small structures in plant cells called chloroplasts. A tree takes in sunlight through the chloroplasts in its leaves. Chlorophyll, a green pigment inside the chloroplasts, absorbs this light energy. Water and carbon dioxide move into the chloroplasts. The tree's roots absorb water from the soil. The water travels to the leaves. Small pores in the leaves called stomata open to let in air. Carbon dioxide from the air combines with the water in a series of chemical reactions that produce glucose and oxygen gas. The stomata release the oxygen into the air as waste. The tree uses matter and energy from the glucose to grow larger and carry out processes needed for survival.

光合作用发生在植物细胞中叫做叶绿体的小结构内。 树木通过树叶中的叶绿体吸收阳光。 叶绿素是叶绿体内的一种绿色色素，吸收这种光能。 水和二氧化碳进入叶绿体。 树根从土壤中吸收水分。 水流向叶子。 叶子上叫做气孔的小气孔打开让空气进入。 空气中的二氧化碳与水在一系列化学反应中结合，产生葡萄糖和氧气。 气孔将氧气作为废物释放到空气中。 这棵树利用葡萄糖中的物质和能量来生长，并进行生存所需的过程。

Growing Downward Even the tallest tree in the world started as a tiny seed. Seeds contain glucose stored by the parent tree. When a seed sprouts, the roots grow downward. Root hairs on the outer layer of each root absorb water and nutrients from the soil. The water travels to the tree's first leaves, where it is used for photosynthesis, providing more glucose for the tiny sprout. The roots use glucose to continue growing in search of water. The tip of each root is covered by a root cap. Under each cap is a root apical meristem (AY-pih-kul MEH-rih-stem)— an area where new cells form rapidly from existing cells that divide, or split in two. This primary growth causes the roots to become longer.

即使是世界上最高的树，一开始也是一颗小小的种子。 种子含有由母树储存的葡萄糖。 种子发芽时，根向下生长。 每根外层的根毛从土壤中吸收水分和养分。 水会流到树的第一片叶子，在那里进行光合作用，为微小的嫩芽提供更多的葡萄糖。 根系利用葡萄糖继续生长以寻找水分。 每根的尖端都被根冠覆盖。 在每个帽下都有一个根尖分生组织(AY-pih-kul MEH-rih-stem)——一个新细胞从分裂或分裂成两个的现有细胞迅速形成的区域。 这种初级生长使根变得更长。

Growing Upward A shoot, made up of a young stem and leaves, also emerges from the seed and pokes up through the soil in search of sunlight. The stem grows upward in the same way roots grow downward. Cells at the shoot apical meristem use matter and energy produced during photosynthesis to divide rapidly. This primary growth at the tip causes the stem to become longer. Small bumps called buds form on either side of the stem. As the stem grows taller, some of the buds elongate into branches, each with its own apical meristem. Additional leaves form on the stem and branches, producing even more glucose. Trees use some of their glucose to produce cones or fruit. These structures contain seeds that may become new trees someday.

向上生长由茎和叶组成的嫩枝也从种子中长出来，从土壤中探出头来寻找阳光。 茎向上生长，与根向下生长的方式相同。 茎尖分生组织的细胞利用光合作用产生的物质和能量迅速分裂。 尖端的初级生长导致茎变长。 茎的两侧形成小凸起，称为芽。 当茎长得更高时，一些芽拉长成分枝，每个分枝都有自己的顶端分生组织。 在茎和树枝上形成额外的叶子，产生更多的葡萄糖。 树木利用其中的一部分葡萄糖来产生球果或果实。 这些结构所包含的种子可能有一天会变成新的树木。

Growing Outward A tree also grows outward, becoming wider. Its stem, or trunk, experiences secondary growth in a layer of cells called the cambium. The cells in the cambium divide to produce long, tube-shaped cells called xylem (ZY-lum) and phloem (FLOW-um). As more xylem and phloem are created, the tree grows wider. Xylem transports water from the roots to the leaves to be used for photosynthesis. Phloem moves food from the leaves to other parts of the tree, where it is used for primary and secondary growth. Wowser! The Tree of Tule in Oaxaca (wah-HAH-kuh), Mexico, has one of the widest trunks in the world, with a diameter of about 11.6 meters (38 ft.). That's about as long as a school bus!

一棵树也向外生长，变得更宽。 它的茎或树干在一层叫做形成层的细胞中经历二次生长。 形成层中的细胞分裂产生长长的管状细胞，称为木质部(ZY-lum)和韧皮部(FLOW-um)。 随着木质部和韧皮部的增多，树越长越宽。 木质部将水从根部输送到叶片，用于光合作用。 韧皮部将食物从树叶转移到树木的其他部位，在那里它被用于初级和二次生长。 老古板!墨西哥瓦哈卡州的图莱树拥有世界上最宽的树干之一，直径约11.6米(38英尺)。 这和一辆校车差不多长!