Abstract Detail


Rong, Huang [1], Huang, Lanqing [1], Lei, Xiaozhou [1], Fang, Chuangwei [1], Castillo-Díaz, Diana [2], Chen, Huayang [3], Wen, Bin [4], Cao, Kun-Fang [1], Zhu, Shidan [1], Manage Goodale, Uromi [1].

Effects of nitrogen and phosphorus addition on early regeneration and root shoot growth in hemiepiphytic and non-hemiepiphytic Ficus species.

Despite having profound effects on growth and survival, the effect of nitrogen (N) and phosphorus (P) deposition on the early regeneration of forest tree species is not well understood. This study investigated the effect of N and P addition on eight hemiphytic (Ficus benjamina L., Ficus concinna (Miq) Miq., Ficus microcarpa L.f., Ficus religiosa L.) and non-hemiphytic (Ficus auriculata Lour, Ficus hispida L.f., Ficus oligodon Miq., Ficus racemosa L.) Ficus species’ early regeneration by subjecting seeds of these species to eight N and P addition treatments: 1) no N and P (N0P0; control treatment), 2) 15 mmolL-1 N  (N1P0); 3) 45mmolL-1 N (N2P0); 4) 70mmolL-1 N(N3P0); 5) 0.6mmolL-1 P (N0P1); 6) 2.6mmolL-1 P(N0P2); 7) 4.6 mmolL-1 P(N0P3); 8) 70mmolL-1 N and 4.6 mmolL-1 P (N3P3).  N was added as NH4NO3 and P was added as KH2PO4. After 90-d growth period (growth chamber conditions: 25/15°C ~ 12/12 hours day/night; humidity: 60% relative humidity; light: PPFD 400 µmol m-2 s-1), the effect of N and P on (1) the root to shoot length ratio, (2) root length, (3) stem length, (4) an index representing the complexity of the root system (sum of taproot presence or absence score, number of primary and secondary(s) and root hair presence or absence score), and (5) an index representing root aging (sum of root color relevant to aging; white = 1, yellow = 2, brown =3) was assessed using general linear mixed models in R statistical program, with growth form and nutrient addition treatment analyzed as fixed factors and species considered as a random factor. The study results show that species’ growth form and nutrient concentration of species were important factors in determining the complexity of root system and the length of tap root and stem, with opposite responses at the low end and high end of nitrogen and phosphorus addition treatments, indicating that root growth has high plasticity to changes in external nutrient availability. High N treatment seedlings showed inhibited root growth in both growth forms indicating a resource conservation strategy. However, higher P addition resulted in root growth stimulation with greater root growth observed in hemiepiphytic species, consistent with what would be expected as they regenerate in nutrient limited substrates on canopy tops and later become terrestrial. Root aging determined by the root color index showed a positive correlation between N addition and root aging with greater aging seen in non-hemiepiphytic species. In contrast, P increase did not affect root aging but increased P addition resulted in greater differences in aging between the two growth forms. These results support previous studies. Hemiepiphytes Ficus species have stronger abiotic stress tolerance, and at the seedling stage, they show an adaptive root growth strategy that support greater nutrient acquisition at these critical life history transition stages, where they are limited in available substrate. This study improves our ecophysiological knowledge of an understudied process -- the early regeneration stage -- in a key ecological group of species that are important forest tree species in tropical and subtropical Asia.

1 - Guangxi University, Forestry College, Daxuedonglu 100, Nanning, Guangxi, 530005, China, (+86)18174128535
2 - Terraformation, Forestry, Kailua-Kona, HI, 96740, USA
3 - Institute Of Botany, The Chinese Academy Of Sciences, State Key Laboratory Of Vegetation And Environmental Change, No.20 Nanxincun, Xiangshan, Beijing, 100093, P.R. China, Beijing, 11, 100093, China
4 - Xishuangbanna Tropical Botanical Garden, Center for Integrative Conservation, Mengla, Yunnan, 666303, China

Early regeneration
Nitrogen addition
Phosphorus addition
Root aging
Root complexity
Root shoot length ratio.

Presentation Type: Oral Paper
Number: EPH2010
Abstract ID:406
Candidate for Awards:Physiological Section Physiological Section Li-COR Prize

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