塊莖與塊根

title: 块茎.
content: 块茎(英语:stem tuber)是多年生植物的根状膨胀地下茎或匍匐茎的一种,属植物保存营养或水分用的贮藏器官,有多年化(过冬耐旱)、无性生殖等作用。其节眼上长出不定根(植物底部)和芽(朝上位置),位于母株的两旁、靠近泥土表面的位置。可见于姜、芋、藕、山药、马铃薯等。  母株的后代及新的块茎一般依附在原有块茎上,或在地下根茎的末端形成。当植物枯萎后,新生块茎的芽会于合适的环境条件演变成拥有茎、叶的子株,原有块茎逐渐枯萎,新的块茎再次形成。一些植物则形成较小的结节状块茎,功能与种子相似,可长成结构、大小与种子相似若的植物。  块茎的寿命因品种而异,长如秋海棠属,但大部分地下块茎的寿命一般都比较短促,仅足以维持新芽成长成为新的植株。  块茎通常开始于幼苗下胚轴部分的扩大,但有时也包括上胚轴的第一或两个节及根的上部。块茎具有垂直方向,顶部有一个或几个营养芽,底部由基部产生,根部有纤维状根,而块茎通常呈长圆形。  块茎秋海棠、yams最常见的块状茎植物。落葵薯 (Anredera cordifolia) 会在3至7米高的藤蔓上长出块状的气茎,之后掉到地上会再继续繁殖。薄荷形唇形科的Plectranthus esculentus会在茎的根部,在地下产生块茎,每个块茎最重可以到1.8 kg,一开始是腋芽,之后再由短茎长成块茎荚果植物很少会形成块茎,玫红山黧豆是亚洲及欧洲的原生种荚果块茎植物,以往人类也曾经种植过。
title: 马铃薯.
content: 我们日常食用的马铃薯为其植株的块茎。其匍匐茎膨胀变厚,发展成为贮藏器官  马铃薯拥有正常茎的所有部分,包括节和节间。节即为马铃薯的芽眼,带有叶痕,芽眼从距离匍匐茎最远端开始、以螺旋般的排列分布在块茎上。顶芽于最远端开始生长,植株因而获得顶端优势。马铃薯块茎的薄壁组织含有大量淀粉,而一般植物茎的髓、皮质及维管束都可以在马铃薯中找到。  地面部分在秋季枯萎后,地下块茎可多年化存活,春天来到,芽会消耗储存的养份演变成拥有茎、叶的子株。新块茎底部形成不定根、芽甚或匍匐茎。日照时间变长,匍匐茎于生长素刺激下加长,根部生长受到抑制。匍匐茎必须达到一定长度,才可形成新的块茎。过程中,脂氧合酶辅助合成的茉莉酸控制马铃薯块茎的生长。  随着营养繁殖代代相传,相比种子种出的母株,后代的匍匐茎变得不易辨认,块茎形成位置越发接近地面,甚至地面可见。因此种植马铃薯时一般会把块茎或种子埋进土壤深处,预留更多空间。短小的匍匐茎在土壤下已开始形成,当梢露出地面,马铃薯将长成有根有叶的绿色植物。
title: 块根.
content: A tuberous root or storage root, is a modified lateral root, enlarged to function as a 贮藏器官. The enlarged area of the root-tuber, or storage root, can be produced at the end or middle of a root or involve the entire root. It is thus different in origin but similar in function and appearance to a stem tuber. Examples of plants with notable tuberous roots include the sweet potato, 木薯, and 大丽菊.  Root tubers are perennating organs, thickened roots that store nutrients over periods when the plant cannot actively grow, thus permitting survival from one year to the next. The massive enlargement of secondary roots typically represented by sweet potato ("番薯"), have the internal and external cell and tissue structures of a normal root, they produce 根 and stems which again produce adventitious roots.  In root-tubers, there are no nodes and internodes or reduced leaves. Root tubers have one end called the proximal end, which is the end that was attached to the old plant; this end has crown tissue that produces buds which grow into new stems and foliage. The other end of the root tuber is called the distal end, and it normally produces unmodified roots. In stem tubers the order is reversed, with the distal end producing stems. Tuberous roots are biennial in duration: the first year the plant produces root-tubers, and at the end of the growing season, the plant shoots often die, leaving the newly generated tubers. The next growing season, the root-tubers produce new shoots. As the shoots of the new plant grow, the stored reserves of the root-tuber are consumed in the production of new roots, stems, and reproductive organs; any remaining root tissue dies concurrently to the plant's regeneration of next generation of root-tubers.  "萱草" plus a number of Daylily hybrids have large root-tubers, "H. fulva" spreads by underground stolons that end with a new fan that grows roots that produce thick root tubers and then send out more stolons.  Root tubers, along with other storage tissues that plants produce, are consumed by animals as a rich source of nutrients. The root-tubers of Arrowhead plants of the genus "茨菰属" are eaten by ducks.  Plants with root tubers are propagated in late summer to late winter by digging up the tubers and separating them, making sure that each piece has some crown tissue for replanting.

Summary: 块茎(英语:stem tuber)及块根(英语:root tuber)均为部分植物物种借助其构造上膨大了的部分而形成的营养素贮藏器官。这些构造存在于多年生植物,用以在其越过冬季或旱季(多年化)之时,得以保留至下一生长季度时为植物的重新生长提供营养及能量,更可用于无性生殖。 块茎(英语:stem tuber)由变粗了的根茎(rhizomes,根状膨胀地下茎)或匍匐茎形成,常见的物种有马铃薯及山药等。部分文献亦将块根(英语:root tuber)包括在内,即外形类似块茎的膨胀侧根,例如:红薯、木薯及大丽菊;其他的或只包括块茎。