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  • Stems Stems Stems Stems Stems Stems Stems Stems Stems Stems Stems Stems Stems 斯丁

    Close-up of a tree trunk displaying its bark and branches, surrounded by green leaves.

    How does water get up? How does sugar move down?
    ::水怎么涨起来 糖怎么降下来

    What structures hold the plant upright? Are tree trunks also stems? Of course they are. Trees don't start out big and tall - they grow from small plants to large trees. And it is these stems that allow them to grow upright. So, obviously the stem is very important and has numerous functions.
    ::树干是长成的吗?树干是长的吗?树干不是长的,树是长的,树不是长的,树是长的,树是长的,树是长的,树是长的,树是长的,树是长的,树是长的,树是长的,树是长的,树是长的,树是长的,树是长的,树是长的,树是长的,树是长的,树是长的,树是长的,树是长的,树是长的,树是长的,树是长的,树是长的,树是长的,树是长的。树是长的,树是长的,树是长的。树是长的。树是长的干,干是重要的,能成的。

    Stems
    ::Stems Stems Stems Stems Stems Stems Stems Stems Stems Stems Stems Stems Stems 斯丁

    In , stems are the organs that hold plants upright so they can get the sunlight and air they need. Stems also bear leaves, flowers , cones, and secondary stems. These structures grow at points called nodes (shown in Figure ). At each node, there is a bud of meristem tissue that can divide and specialize to form a particular structure.
    ::根部是保持植物直立的器官,这样它们就能得到它们所需要的阳光和空气。 Stems还生着叶子、花朵、锥子和副茎。这些结构在被称为节点的地方生长(图中显示 ) 。 在每一个节点上,都有一个细胞组织芽,可以分割和专门形成一个特定的结构。

    Plant anatomy with labels for stem, leaf, node, petiole, and axil.

    The stem of a vascular plant has nodes where leaves and other structures may grow.
    ::血管植物的干部有节点,叶子和其他结构可能生长。

    Another vital function of stems is transporting and minerals from to leaves and carrying food from leaves to the rest of the plant. Without this connection between roots and leaves, plants could not survive high above ground in the air. In many plants, stems also store food or water during cold or dry seasons.
    ::木茎的另一个重要功能是从树叶运输矿物,并将食物从叶子运到植物的其他地方,如果没有根叶和叶叶之间的这种联系,植物就无法在空气中高地生存,许多植物在寒季或旱季也储存着食物或水。

    Stem Diversity
    ::Stem 多样性

    Stems show variation because many stems are specialized. Figure shows examples of stem specialization . With specialized stems, plants can exploit a diversity of niches in virtually all .
    ::由于许多树枝是专门化的,因此树木的刺状变化很大。图中显示了干茎专业化的例子。有了专门化的刺状,植物可以几乎在所有地方利用不同的缝隙。

    Examples of specialized stems showing adaptations for various habitats.

    Stem specializations such as these let plants grow in many different habitats.
    ::植物生长在许多不同的生境中,这些植物可以生长。

    Stem Tissues and Functions
    ::Stem 标准组织与函数

    Like roots, the stems of vascular plants are made of dermal, vascular, and .
    ::像根一样,血管植物的根由皮肤、血管和... ...组成。

    • A single-celled layer of epidermis protects and waterproofs the stem and controls gas exchange.
      ::单细胞层的皮层保护干燥和控制气体交换,防水。
    • In trees, some of the epidermal tissue is replaced by bark . Bark is a combination of tissues that provides a tough, woody external covering on the stems of trees. The inner part of bark is alive and growing; the outer part is dead and provides strength, support, and protection.
      ::在树上,有些上皮组织被树皮取代。 牛头组织是由组织组成的组合,为树根提供了坚硬、木质的外部覆盖。 树皮的内部是活的和成长的;外部是死的,提供了力量、支持和保护。
    • Ground tissue forms the interior of the stem. The large central vacuoles of ground tissue fill with water to support the plant. The cells may also store food.
      ::地面组织构成干叶的内部,地面组织的大量中央真空填满水以支撑植物,细胞也可能储存食物。
    • Bundles of run through the ground tissue of a stem and transport fluids. Plants may vary in how these bundles are arranged.
      ::干液和运输液在地面组织中运行的捆包,这些捆包的排列方式各有不同。

    Stem Growth
    ::硬增长

    The stems of all vascular plants get longer through primary growth . This occurs in primary meristem at the tips and nodes of the stems. Most stems also grow in thickness through secondary growth . This occurs in secondary meristem , which is located in and around the vascular tissues. Secondary growth forms secondary vascular tissues and bark. In many trees, the yearly growth of new vascular tissues results in an annual growth ring like the one in Figure . When a tree is cut down, the rings in the trunk can be counted to estimate the tree’s age.
    ::所有血管植物的根部都通过初级生长而变得更长。这发生在根部的尖尖和节点的初级中间部中。多数也是通过二次生长而增厚的。这种情况发生在位于血管组织内和周围的二级中间部中。二次生长形成二级血管组织和树皮。在许多树中,新的血管组织年增长导致像图中那样的年生长环。当一棵树被砍倒时,树干中的环可以算作估计树龄。

    Cross-section of a tree trunk showing growth rings used to estimate age.

    The number of rings in this cross-section of tree trunk show how many years the tree lived. What does each ring represent?
    ::树干横截面的圆环数显示树活了多少年。 每个环代表什么?

       

     

    Summary
    ::摘要

    • Stems hold plants upright, bear leaves and other structures, and transport fluids between roots and leaves.
      ::树根和树叶之间流动流体
    • Like roots, stems contain dermal, ground, and vascular tissues.
      ::像根一样,根部含有皮肤、地面和血管组织。
    • Trees have woody stems covered with bark.
      ::树上树有木茎,树皮覆盖着树皮。

    Review
    ::回顾

    1. Describe two types of specialized stems. What is each type of stem specialized for?
      ::描述两种特殊的干茎。每种类型的干茎都专门用于什么?
    2. What is bark? What purposes does it serve?
      ::什么是叫声?它服务于什么目的?
    3. Apply lesson concepts to predict how the stem of a desert plant might be specialized for its environment.
      ::应用经验概念来预测沙漠植物的干部如何专门用于环境。