蕁麻科樓梯草屬植物瘦果的補充描述

陳小勤 符龍飛 溫放 黎舒 劉影 韋毅剛

摘要： 樓梯草屬植物的瘦果具有較高的形態多樣性，可作為種類鑒定的重要依據。然而，中國超過半數樓梯草屬植物缺少瘦果形態信息。該研究通過野外考察、標本查閱以及光鏡和掃描電鏡的觀察，對七種樓梯草屬植物的瘦果進行了補充描述，并提供了墨線圖和照片。該研究結果對該屬的進一步分類修訂提供了有價值的信息。

關鍵詞： 補充描述， 瘦果， 樓梯草屬， 掃描電鏡

Elatostema Forster & Forster comprises around 500 species of herbs， small shrubs and subshrubs （Wang， 2014） that grow in deep shade in forests， stream sides， gorges and caves. Elatostema is mainly distributed in tropical and subtropical regions of Africa， Asia and Oceania （Wang， 1995； Lin et al， 2003）. The latest revision for Chinese Elatostema was put forward by Wang （2014） that contained 280 species， of which 108 species were endemic.

Elatostema species are difficult to distinguish due to the tiny flowers， variation in staminate tepal number and the reduced nature of pistillate tepals which reduced the available number of characters for species delimitation （Fu et al， 2014）. The achene is one of important morphological characters in determining systematic position， evolutionary level and infragenetic relationship of Elatostema， as well as delimiting series （Wu et al， 2012； Wang， 2014）. Wang （2014） concluded ten types of achenes： （1） ribbed， （2） ribbed and puncticulate， （3） ribbed and tuberculate， （4） ribbed， tuberculate and winged， （5） tuberculate， （6） tuberculate and reticulatestriate， （7） smooth， （8） puncticulate， （9） lineolate and （10） lineolate and tuberculate. Despite the high morphological diversity of achene in this genus provides a useful character in delimitation， over half of Chinese species are lacking of achene information （Wang， 2014）.

In this paper， we aimed to supplement the description of achene based on our field collection and specimen checking by light microscope （LM） and scanning electron microscope （SEM） to provide valuable information for further taxonomic revision in this genus.

1 Materials and Methods

The mature achenes of seven species were carefully collected from specimen by tweezer for LM and SEM observation. For each species， 3-10 achenes were used to determine the size and shape. All the voucher specimens were deposited in the herbarium of Guangxi Institute of Botany （IBK）. The illustration for each species was also drawn based on LM and SEM photos.

For LM， achenes were examined under a XTZD binocular microscope and Plan Apo lens at × 20 magnifications. Photos were taken by Canon G12 camera.

For SEM， achenes were placed in a bathtype ultrasonic cleaner for 10 min with 70% ethanol to remove the impurity. After airdrying， the achenes were mounted on the stubs using doublesided adhesive tape and coated with gold in a sputter coater. The coated achenes were observed and photographed under ZEISSE VO18 scanning electron microscope. The achene size was measured on photo of SEM by the ImagePro Plus. The achene shape and surface were followed Liu et al （2004） and Wang （2014）.

2 Results and Discussion

2.1 Elatostema angulaticaule W. T. Wang & Y. G. Wei in Guihaia 29（6）： 716. 2009.

Achenes brownish， ellipsoid， 0.558-0.618 × 0.266-0.322 mm， length：width ratio 1.9-2.1：1， longitudinally 6ribbed （Fig. 1： A； Fig. 2： A； Fig. 3： A）.

Voucher specimen：

Guangxi： Xilin County， Guzhang， 7 June 2006， Y. G. Wei 06178 （IBK）.

Elatostema angulaticaule is the most similar to E. tenuifolium W. T. Wang （Wei & Wang， 2009）. The differences of achene between two species are that the former one has smaller size （0.558-0.618 × 0.266-0.322 mm vs. 1 × 0.6-0.8 mm） and surface with longitudinally 6ribbed （vs. longitudinally 6ribbed and sparsely tuberculate）.

2.2 Elatostema heterocladum W. T. Wang. A. K. Monro & Y. G. Wei in Phytotaxa 147（1）： 7. 2013.

Achenes brownish， ellipsoid， 0.790-0.985 × 0.412-0.499 mm， length：width ratio 1.8-2.3：1， longitudinally 4ribbed， and between each pair of ribs sparsely tuberculatepuncticulate （Fig. 1： B； Fig. 2： B； Fig. 3： B）.

Voucher specimen：

Guangxi：Longzhou County， Banbi， April 2011， Y. G. Wei & F. Wen 1176 （IBK）.

Elatostema heterocladum is the most similar to E. androstachyum W. T. Wang， A. K. Monro & Y. G. Wei （Wei et al， 2013）. The differences of achene between two species are that the former one is brownish （vs. beige）， has bigger size （0.790-0.985 × 0.412-0.499 Fig. 1Illustration of achenes of seven Elatostema speciesA. E. angulaticaule W. T. Wang & Y. G. Wei； B. E. heterocladum

W. T. Wang. A. K. Monro & Y. G. Wei； C. E. obscurinerve W. T. Wang； D. E. planinerve W. T. Wang & Y. G. Wei；

E. E. pseudolongipes W. T. Wang & Y. G. Wei； F. E. longibracteatum W. T. Wang； G. E. subtrichotomum

W. T. Wang. The same below. （Illustrated by LIN WenHong）

Fig. 2LM photos of achenes of seven Elatostema species

Fig. 3SEM photos of achenes of seven Elatostema species

mm vs. ca. 0.65 × 0.3 mm） and surface with longitudinally 4ribbed， and between each pair of ribs sparsely tuberculatepuncticulate （vs. 5 longitudinal ribs）.

2.3 Elatostema obscurinerve W. T. Wang in Bull. Bot. Lab. N. E. Forest. Inst. 7： 63. 1980.

Achenes brownish， ellipsoid， 0.550-0.741 × 0.283-0.355 mm， length： width ratio 1.9-2.1：1， longitudinally 6ribbed （Fig. 1： C； Fig. 2： C； Fig. 3： C）.

Voucher specimen：

Guangxi： Fengshan County， Yunfeng Cave， 27 April 2011， Y. G. Wei & F. Wen C005E1 （IBK）.

Elatostema obscurinerve is the most similar to E. involucratum Franch. et Sav. （Wang， 1980）. The differences of achene between two species are that the former one has smaller size （0.550-0.741 mm vs. 0.7-0.8 mm） and surface with longitudinally 6ribbed （vs. longitudinally 6ribbed and tuberculate）.

2.4 Elatostema planinerve W. T. Wang & Y. G. Wei in Nordic J. Bot. 30： 1. 2012.

Achenes brownish，ellipsoid， 0.552-0.566 × 0.297-0.331 mm， length：width ratio 1.7-1.8：1， longitudinally 6ribbed （Fig. 1： D； Fig. 2： D； Fig. 3： D）.

Voucher specimen：

Guizhou： Xingyi City，31 March 2010， Y. G. Wei & F. Wen 1027 （IBK）.

Elatostema planinerve is the most similar to E. bracteosum （Wen et al， 2012）. The differences of achene between two species are that the former one has smaller size （0.552-0.566 mm vs. 0.7-1 mm） and surface with longitudinally 6ribbed （vs. longitudinally 6ribbed and tuberculate）.

2.5 Elatostema pseudolongipes W. T. Wang & Y. G. Wei in Elatostema （Urticaeae） in China 279. 2014.

Achenes brownish， ellipsoid， 0.618-0.682 × 0.366-0.398 mm， length：width ratio 1.6-1.8：1， tuberculate （Fig. 1： E； Fig. 2： E； Fig. 3： E）.

Voucher specimen：

Guangxi： Longzhou County， Banbi， 21 May 2010， Y. G. Wei & A. K. Monro AM6813 （IBK）.

Elatostema pseudolongipes is the most similar to E. longipes W. T. Wang （Wang， 2014）. The differences of achene between two species are that the former one has smaller size （0.618-0.682 mm vs. ca. 0.8 mm） and surface with tuberculate （vs. longitudinally 6ribbed）.

2.6 Elatostema longibracteatum W. T. Wang in Bull. Bot. Res. Harbin 2（1）： 6. 1982.

Achenes brownish， ellipsoid， 0.540-0.687 × 0.243-0.293 mm， length：width ratio 2.0-2.5：1， longitudinally 68ribbed （Fig. 1： F； Fig. 2： F； Fig. 3： F）.

Voucher specimen：

Yunnan： Malipo County， Niuchang Village， 2 May 2013，L. F. Fu & S. L. Huang FL0020 （IBK）.

Elatostema longibracteatum is the most similar to E. asterocephalum W. T. Wang （Wang， 1982）. The differences of achene between two species are that the former one has smaller size （0.540-0.687 mm vs. 0.8 mm） and surface with longitudinally 68ribbed （vs. longitudinally 68ribbed and tuberculate）.

2.7 Elatostema subtrichotomum W. T. Wang in Bull. Bot. Lab. N. E. Forest. Inst. 7： 25. 1980.

Achenes brownish， ovoidellipsoid， 0.600-0.664 × 0.277-0.336 mm， length：width ratio 1.8.0-2.3：1， longitudinally 45ridded， between each pair of ribs sparsely tuberculate and two opposite rids winged （Fig. 1：G； Fig. 2： G； Fig. 3： G）.

Voucher specimen：

Guizhou： Guiyang City， Zijiang Difeng， 16 May 2012， Y. H. Tseng & L. F. Fu Zn1267 （IBK）.

Elatostema subtrichotomum is the most similar to E. oblongifolium Fu ex W. T. Wang （Wang， 1980）. The differences of achene between two species are that the former one has smaller size （0.600-0.664 mm vs. 0.8-0.9 mm） and surface with longitudinally 45ridded， between each pair of ribs sparsely tuberculate and two opposite rids winged （vs. longitudinally 6ribbed）.

AcknowledgementsWe would like to thank LIN WenHong for the illustration and Dr. DONG LiNa for her constructive suggestions on the manuscript. We also thank the herbarium of Guangxi Institute of Botany （IBK） for checking specimens.

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