Can you summarize the following document?
        
  塊莖(英語:stem tuber)是多年生植物的根狀膨脹地下莖或匍匐莖的一種,屬植物儲存營養或水分用的貯藏器官,有多年化(過冬耐旱)、無性生殖等作用。其節眼上長出不定根(植物底部)和芽(朝上位置),位於母株的兩旁、靠近泥土表面的位置。可見於姜、芋、藕、山藥、馬鈴薯等。  母株的後代及新的塊莖一般依附在原有塊莖上,或在地下根莖的末端形成。當植物枯萎後,新生塊莖的芽會於合適的環境條件演變成擁有莖、葉的子株,原有塊莖逐漸枯萎,新的塊莖再次形成。一些植物則形成較小的結節狀塊莖,功能與種子相似,可長成結構、大小與種子相似若的植物。  塊莖的壽命因品種而異,長如秋海棠屬,但大部分地下塊莖的壽命一般都比較短促,僅足以維持新芽成長成為新的植株。  塊莖通常開始於幼苗下胚軸部分的擴大,但有時也包括上胚軸的第一或兩個節及根的上部。塊莖具有垂直方向,頂部有一個或幾個營養芽,底部由基部產生,根部有纖維狀根,而塊莖通常呈長圓形。  塊莖秋海棠、yams最常見的塊狀莖植物。落葵薯 (Anredera cordifolia) 會在3至7米高的藤蔓上長出塊狀的氣莖,之後掉到地上會再繼續繁殖。薄荷形脣形科的Plectranthus esculentus會在莖的根部,在地下產生塊莖,每個塊莖最重可以到1.8 kg,一開始是腋芽,之後再由短莖長成塊莖莢果植物很少會形成塊莖,玫紅山黧豆是亞洲及歐洲的原生種莢果塊莖植物,以往人類也曾經種植過。

  我們日常食用的馬鈴薯為其植株的塊莖。其匍匐莖膨脹變厚,發展成為貯藏器官  馬鈴薯擁有正常莖的所有部分,包括節和節間。節即為馬鈴薯的芽眼,帶有葉痕,芽眼從距離匍匐莖最遠端開始、以螺旋般的排列分佈在塊莖上。頂芽於最遠端開始生長,植株因而獲得頂端優勢。馬鈴薯塊莖的薄壁組織含有大量澱粉,而一般植物莖的髓、皮質及維管束都可以在馬鈴薯中找到。  地面部分在秋季枯萎後,地下塊莖可多年化存活,春天來到,芽會消耗儲存的養份演變成擁有莖、葉的子株。新塊莖底部形成不定根、芽甚或匍匐莖。日照時間變長,匍匐莖於生長素刺激下加長,根部生長受到抑制。匍匐莖必須達到一定長度,才可形成新的塊莖。過程中,脂氧合酶輔助合成的茉莉酸控制馬鈴薯塊莖的生長。  隨著營養繁殖代代相傳,相比種子種出的母株,後代的匍匐莖變得不易辨認,塊莖形成位置越發接近地面,甚至地面可見。因此種植馬鈴薯時一般會把塊莖或種子埋進土壤深處,預留更多空間。短小的匍匐莖在土壤下已開始形成,當梢露出地面,馬鈴薯將長成有根有葉的綠色植物。

  A tuberous root or storage root, is a modified lateral root, enlarged to function as a 貯藏器官. 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 大麗菊.  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 "茨菰屬" 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.
塊莖(英語:stem tuber)及塊根(英語:root tuber)均為部分植物物種藉助其構造上膨大了的部分而形成的營養素貯藏器官。這些構造存在於多年生植物,用以在其越過冬季或旱季(多年化)之時,得以保留至下一生長季度時為植物的重新生長提供營養及能量,更可用於無性生殖。 塊莖(英語:stem tuber)由變粗了的根莖(rhizomes,根狀膨脹地下莖)或匍匐莖形成,常見的物種有馬鈴薯及山藥等。部分文獻亦將塊根(英語:root tuber)包括在內,即外形類似塊莖的膨脹側根,例如:紅薯、木薯及大麗菊;其他的或只包括塊莖。