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Abstract: The decline in seedling growth of Malania oleifera as the age increases is often observed in the absence of host
plants. A better knowledge of nutrient dynamics in terms of concentration and distribution patterns in different parts of
the declining seedlingsꎬ the concentrations of Nꎬ Pꎬ and K were comparatively analyzed in various organs of unattached
M. oleifera seedlings grown for half a yearꎬ two yearsꎬ and three years. Additionallyꎬ the starch content and distribution
patterns in the roots and stems of seedlings with different vigor levels were qualitatively assessed by staining cross ̄
sections. The results were as follows: (1) As the growth vigor of M. oleifera seedlings declinedꎬ the concentrations of Nꎬ
Pꎬ and K in most organs decreasedꎬ except for a significant increase in K concentration in lateral roots. The leaf N/ P
ratios of the declining seedlings became increasingly imbalancedꎬ indicating different nutrient deficiency types among the
seedlings with varying decline degrees. Unattached M. oleifera seedlings grown for half a year were primarily limited by
insufficient N supply (with an average N/ P ratio of 11.33) and subsequently by P limitation after two years (average N/
P ratio 17.81). The leaf N/ P ratio of unattached M. oleifera seedlings grown for three years was remarkably imbalanced
(with an average value of 52.46). As the growth vigor of unattached three ̄year seedlings was considerably lowꎬ they are
deemed unsuitable for afforestation. (2) A decrease in starch content was observed in declining seedlingsꎬ as evidenced
by the reduced staining intensity of cross ̄sections. After three yearsꎬ the starch content of unattached M. oleifera
seedlings was found to have decreased to an extremely low level. Significant differences in starch content were observed at
various locationsꎬ including the connecting point of the stems and rootsꎬ the basal swelling top of the rootꎬ the main rootꎬ
and lateral rootsꎬ among seedlings with different degrees of decline. These findings suggested that starch content levels
could serve as crucial criteria for evaluating the growth vigor of seedlings. Specificallyꎬ lateral roots were identified as
optimal sampling materials for assessing seedling growth vigor through a minimally invasive method. Given the gradual
decline in vitality and decreased nutrient content observed in M. oleifera seedlings grown in the absence of a host plantꎬ
it is recommendedꎬ during the propagation phaseꎬ to ensure adequate mineral nutrient supplementationꎬ select
appropriate host plants for cultivationꎬ and facilitate early ̄stage transplantation. This proactive approach serves to
mitigate a potential decline in survival rates during afforestationꎬ attributed to the reduced vitality of the seedlings. The
results of this study provide valuable information for evaluating seedling growth vigor and offer scientific guidance for
rational fertilization in M. oleifera nurseries.
Key words: root hemiparasitic plantꎬ macromineral elementsꎬ starchꎬ staining of tissue sectionsꎬ growth vigor of
seedlingsꎬ study of rare and endemic plants
蒜 头 果 ( Malania oleifera ) 是 铁 青 树 科 生长ꎬ移栽成活率极低ꎬ从而造成重大经济和人力
(Olacaceae)蒜头果属(Malania) 的常绿乔木(李树 损失ꎮ 如何在幼苗表现出明显的生长衰退现象之
刚ꎬ1980)ꎬ是我国西南特有的珍贵油料植物(欧乞 前ꎬ通过合理施肥改善幼苗长势ꎬ并在移栽前简便
鍼ꎬ1981)和富含神经酸的珍稀资源植物(薛冰和邵 快捷地筛选壮苗ꎬ避免使用衰退幼苗造林导致土地
志凌ꎬ2015)ꎬ也是喀斯特地区生态恢复和石漠化治 资源、人力、物力等的浪费ꎬ是蒜头果栽培造林过程
理的优良树种(吕仕洪等ꎬ2016ꎻ卯吉华等ꎬ2018)ꎮ 中急需解决的一个难题ꎮ
在蒜头果的栽培造林过程中ꎬ将蒜头果种子在育苗 养分是影响植物生长发育最重要的因素之一
圃播种ꎬ然后进行幼苗移栽是一种常用的造林模 (Zhao et al.ꎬ 2005ꎻ Yang et al.ꎬ 2021ꎻ Zhang et
式ꎮ 然而ꎬ由于蒜头果是一种根部半寄生植物(Li et al.ꎬ 2021)ꎮ 植株对营养元素的吸收效率和养分
al.ꎬ 2019ꎻ 李勇鹏等ꎬ2019)ꎬ其幼苗虽然有较多侧 同化能力与植物生长发育紧密相关( De Graaf et
根ꎬ也具备一定的光合能力ꎬ但是养分吸收水平和 al.ꎬ 1998ꎻ Güsewell & Koerselmanꎬ 2002ꎻ Luo et
光合效率较低(李悦ꎬ2021)ꎮ 在育苗圃没有寄主植 al.ꎬ 2021)ꎮ 蒜头果种子硕大( 郭方斌等ꎬ2018)ꎬ
物的条件下ꎬ随着独立生长时间的延长或受环境胁 储存有丰富的营养物质(苏霁玲等ꎬ2021)ꎬ可为种
迫ꎬ蒜头果幼苗活力逐渐衰退(李悦ꎬ2021)ꎮ 根据 子萌发和幼苗建成初期提供必需的养分ꎮ 在没有
前期的栽培经验ꎬ生长严重衰退的蒜头果幼苗移栽 与寄主建立寄生关系之前ꎬ蒜头果幼苗的养分组
后即使追施肥料或配植优良寄主也无法恢复正常 成包括种子储存的养分以及自身吸收合成的养分