Gentallan Jr., Altoveros, Borromeo, Hadsall and Timog (2018). Seed Science and Technology, 46, 1, 191-196. https://doi.org/10.15258/sst.2018.46.1.18
Research Note
Hemi-cryptocotylar epigeal germination of Koordersiodendron
pinnatum (Anacardiaceae) framed according to the BBCH scale
Renerio P. Gentallan Jr.1*, Nestor C. Altoveros1, Teresita H. Borromeo1, Annalee S. Hadsall2 and Emmanuel Bonifacio S. Timog1
1 Institute of Crop Science, College of Agriculture and Food Science, University of the Philippines Los Baños, College, Laguna, Philippines 2 Institute of Biological Sciences, College of Arts and Sciences, University of the Philippines Los Baños, College, Laguna, Philippines * Author for correspondence (E-mail: [email protected])
(Submitted October 2017; Accepted February 2018; Published online April 2018)
Abstract
This study specifically classifies Koordersiodendron pinnatum, an indigenous tree in the Philippines with economic potential, to have epigeal hemi-cryptocotylar germination with reserved storage cotyledons. Thirty K. pinnatum seeds were planted and observed regularly for morphological growth and developmental changes until the first two true leaves unfolded. The hemi-cryptocotyly of K. pinnatum is attributed to the partially photosynthetic cotyledons that are able to intercept light upon elongation at the proximal end of the cotyledons during epicotyl elongation phase (BBCH 019). The difference between cryptocotyly and hemi-cryptocotyly is highlighted. This study also demonstrates the function of the extended BBCH scale in characterising the germination process.
Keywords: Anacardiaceae, Biologische Bundesanstalt, Bundessortenamt und Chemische Industrie (BBCH) scale, germination pattern, hemi-cryptocotyly, Koordersiodendron pinnatum
Experimental and discussion
Depending on the position of cotyledon(s) with respect to the soil, seedling growth and development are generally classified to be either hypogeal or epigeal. Due to its limited nature in characteristically describing the process of seed establishment, Duke (1965) proposed an additional way to describe the process based on cotyledon emergence from the seed coat: phaneroctylar or cryptocotylar. More morphological types from
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191 RENERIO P. GENTALLAN JR., NESTOR C. ALTOVEROS, TERESITA H. BORROMEO, ANNALEE S. HADSALL AND EMMANUEL BONIFACIO S. TIMOG the basic four have been proposed by de Vogel (1979) and Ng (1991). However, upon review, the previous classification has only been expanded to five seedling functional types upon inclusion of the parameter ‘cotyledon texture’ (Garwood, 1996). Recently, this classification has been recognised as a standard measure of characterising seedling functional morphology denoting its potential effects on the fitness of the individual plant (Pérez-Harguindeguy et al., 2016). These seed morphological traits play a potential role in adaptation, particularly in resource capture and response to mortality agents, among others (Fenner, 1985; Onyekwelu, 1990). Aside from this, seedling morphology has also been found to vary across different taxa (de Vogel, 1979); thus, Ibarra-Manri’quez (2001) highlighted the potential taxonomic importance of seedling morphology type indicating that there is “strong phylogenetic inertia among species of the same family and genus”. Locally known as “amugis”, Koordersiodendron pinnatum Merr. is indigenous to the Philippines. The tree belongs to the family Anacardiaceae where other economically- important fruit-bearing species, such as cashew and mango, are circumscribed (Coronel, 2011). Aside from its unutilised edible sweet fruits, the wood is used for construction and other industrial purposes (Fernando et al., 2004); whereas, the exudate has observed medicinal properties (Ding Hou, 1978). With the local importance and limited distribution of the species, few studies have been found to deal with the seedling growth and development of K. pinnatum; currently, however, the species is characterised to exhibit cryptocotylar epigeal germination (de Vogel, 1980; Carmello-Guerreiro and Paoli, 1999). With the advent of the Biologische Bundesanstalt, Bundessortenamt und Chemische Industrie (BBCH) scale by Hack et al. (1972), the pattern of development in the germination stage is described independent of variation in timing, facilitating a standard method of recording and presenting plant growth stages in detail. Hence, given the distinctive development and economic potential of the crop, and the agricultural, ecological and taxonomic advantage of identifying the detailed seed germination pattern, this study aimed to elucidate the seedling growth and developmental stages of Koordersiodendron pinnatum using the extended BBCH scale. A slightly modified procedure from Gentallan Jr. et al. (2017) was used to elucidate the seed germination pattern of Koordersiodendron pinnatum based on the extended BBCH scale of Hack et al. (1972). Given the standard and prescribed minimum of five developed individuals in characterising seedling morphology type (Pérez-Harguindeguy et al., 2016), 30 K. pinnatum seeds from the RC fruit conservation farm (Coronel, 2013) were used. The seeds were planted directly beneath the sterile sand surface under greenhouse conditions. The growth and development of seeds were monitored and noted through morphological observations made three to four times a week until the first compound leaf unfolded. The BBCH scale of seedling growth and developmental stages of K. pinnatum was represented by a three-digit code. The first, second and third digits of the scale correspond to the principal growth stage, mesostage and secondary growth stage, respectively. Each growth stage was then described using numbers from 0 to 9 in ascending order denoting the sequence of the growth stages in time. The germination pattern of K. pinnatum was elucidated by the germination (stage 0) and leaf development (stage 1) of the BBCH scale (table 1).
192 HEMI-CRYPTOCOTYLAR EPIGEAL GERMINATION OF KOORDERSIODENDRON PINNATUM
Table 1. Description of phenological growth stages of Koordersiodendron pinnatum using the Biologische Bundesanstalt, Bundessortenamt und Chemische Industrie (BBCH) scale.
BBCH code Description
Principal Growth Stage 0 000 Fresh seed 001 Start of seed imbibition 003 Completion of seed imbibition 005 Radicle emergence 006 Radicle elongation 016 Lateral root formation 007 Hypocotyl breaking through seed coat 008 Hypocotyl with cotyledons grow towards the soil surface 009 Emergence: cotyledons break through the soil surface 019 Epicotyl elongation and cotyledon extension
Principal Growth Stage 1 100 First two true imparipinnately-compound leaves unfold
Koordersiodendron pinnatum seeds begin the germination process through the cha- racteristic emergence of the radicle at the stylar-end of the seed (BBCH 005). After the radicle elongates (BBCH 006) and lateral roots develop (BBCH 016), the hypocotyl breaks through the seed coat (BBCH 007) and, subsequently elongates (BBCH 008) carrying the cotyledons above the soil surface (BBCH 009). Finally, the epicotyl elongates (BBCH 019) and, subsequently, the first two imparipinnately-compound leaves with seven leaflets unfold in the opposite arrangement, concluding the germination process (figure 1). During seedling development, the fleshy cotyledons remain inside the testa; they eventually drop off upon complete utilisation of food reserves during the leaf development stage (BBCH stage 1). This pattern of development is described as hemi-cryptocotylar by Conran et al.
(1997), also observed in Drosera adelae F. Muell. and other Droseraceae species where the apex of the cotyledon becomes non-emergent but the remaining part of the cotyledon emerges forming a “photosynthetic cotyledon loop”. Hence, in this case, the cryptocotylar epigeal germination is further described to have cotyledons which completely remain inside the seed coat that remain non-photosynthetic throughout the plant’s life cycle. This true epigeal cryptocotylar germination is exemplified by Anacolosa frutescens Blume and Rollinia salicifolia Schltdl. where non-photosynthetic cotyledons become abscised prior to leaf unfolding (Franceschini, 2004; Gentallan Jr. et al., 2017). The described development validates the observations of de Vogel (1980) wherein K. pinnatum is classified as having a Heliciopsis-type, Koordersiodendron-subtype of seedling. However, instead of completely inhibiting photosynthesis in the cotyledon, in the case of K. pinnatum, the growth of the
193 RENERIO P. GENTALLAN JR., NESTOR C. ALTOVEROS, TERESITA H. BORROMEO, ANNALEE S. HADSALL AND EMMANUEL BONIFACIO S. TIMOG
000 10 mm 005 10 mm 006 10 mm
009 10 mm 019 10 mm
100 30 mm 100 30 mm
Figure 1. Major growth stages of Koordersiodendron pinnatum framed from the extended BBCH scale (number in top left of each image; see table 1).
194 HEMI-CRYPTOCOTYLAR EPIGEAL GERMINATION OF KOORDERSIODENDRON PINNATUM proximal parts of the two cotyledons permits some light interception during the epicotyl elongation (BBCH 019) resulting in partially photosynthetic cotyledons. This is the first detailed elucidation and report of epigeal hemi-cryptocotyly in the family Anacardiaceae but may also be present in the Swintonia (de Vogel, 1980), Madhuca (Mundhra and Paria, 2009) and Clerodendrum (Ghosh and Pal, 2015) genera, and other species characterised to have Heliciopsis type-Koordersiodendron subtype seedlings. Based on the standard functional morphological type of seedlings (Garwood, 1996; Pérez-Harguindeguy et al., 2016), K. pinnatum seedlings are classified as cryptocotylar epigeal with reserve storage cotyledons (CER). This germination type is considered to be a primitive character among seedling morphotypes. The seedling pushes the cotyledons above the soil with the goal of facilitating cotyledonary photosynthesis; however, in epigeal cryptocotylar seedlings, the cotyledons remain inside the testa obstructing light from reaching the cotyledon. This seedling developmental pattern is considered to be unusual and is only exemplified by one to few species per family. The hemi-cryptocotylar epigeal seedling type, however, may be a more advanced trait allowing partial photosynthesis and protection of the cotyledons during seedling development. Moreover, epigeal phanerocotyly, hypogeal cryptocotyly and epigeal cryptocotyly exist within the same family (Pell et al., 2001), indicating that the seedling morphological types can be potentially used for taxonomic delineation within the taxon.
References
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