Morphological Development of Primary Laticifers in Shoots of Hevea brasiliensis Muell. Arg

doi:10.3969/j.issn.1000-2561.2020.05.006

Abstract

Abstract:

The primary laticifers of Hevea brasiliensis Muell. Arg present mainly in young trunks, shoots, leaves, flowers, and fruits. However, its morphological development is unknown. Two methods, parafin section and modified alkali-treated stripping were used to study the development of the primary laticifers in this study, and the latter was found superior to the former by continuous observation of the whole developmental process. The morphological development of the primary laticifers of different stages was systematically investigated using the modified alkali-treated stripping method. The results showed that the laticifers isolated from different positions of the bronze-stage shoots were morphologically distinct. The laticifers close to the apical meristem were longtube-like linear structures without end-walls and branches, and protrusive growth was not obvious. The lacifers at 7 cm away from the apical meristem had obvious intrusive growth and bead-like structures, which resulting in increase in the diameter of laticifers. The laticifers at 14 cm away from the apical meristem were significantly enlarged in diameter, and contained more bead-like structures, and the bead-like structures between the neighboring laticifers were connected to form laticifer bridges, which resulting in the formation of a laticifer network. The laticifers isolated from different positions of the stable-stage shoots were morphologically similar, and the density of the protrusions or bead-like structures and the laticifer bridges was significantly higher than that in bronze-stage shoots, and complex laticifer networks were formed in the barks at all positions. The primary laticifers were proved to be multinuclear as well. The results of this study indicate that the primary laticifers in the rubber tree shoots are non-articulated and anastomosing, and belong to a novel type of laticifers. This study would play an important role in the fundamental research of the plant laticifer development.

Key words: Hevea brasiliensis Muell. Arg, primary laticifer, novel type of laticifer, non-articulated and anastomosing laticifer

CLC Number:

S794.1

TAN Deguan,Anuwat KUMPEANGKEAW,HAN Bingying,FU Lili,SUN Xuepiao,ZHANG Jiaming. Morphological Development of Primary Laticifers in Shoots of Hevea brasiliensis Muell. Arg[J]. Chinese Journal of Tropical Crops, 2020, 41(5): 881-887.

Figures/Tables 5

Fig. 1 Comparison of parafin section method and modified stripping method in studies of primary laticifers in rubber tree shoots A, B, C: longitudinal paraffin section of the primary laticifers at 14 cm away from the apical meristem of bronze-stage shoots. D and E: partially isolated primary laticifers using modified stripping method isolated from the same position of bronze-stage shoots, and E is the 3D image of primary laticifers. Blue arrows indicated primary laticifers; red arrows indicatd laticifer bridges; green arrows indicated protrusions or bead-like structures; purple arrows indicated suspected articulated structures. Bars=40 μm。

Fig. 2 Morphological development of primary laticifers in rubber tree shoots revealed by observation of isolated laticifers A-F: Bronze-stage; G-I: Stable-stage. A: A bronze-stage shoot. B-D: Primary laticifers near apical meristems. E: Primary laticifers at 7 cm away from the apical meristem; F: Primary laticifers at 14 cm away from the apical meristems. G: A stable-stage shoots. H: Primary laticifers near the apical meristem. I: Primary laticifers at 7 cm away from the apical meristems. Blue arrows indicated primary laticifers; green arrows indicated protrusions or bead-like structures; red arrows indicated laticifer bridges. B-D: Unstained with iodine-bromine solution; E、F、H、I: Stained with iodine-bromine solution. A and G: Bars=1 cm; B-F, H and I: Bars= 40 μm.

Tab. 1 Morphological development of primary laticifers at different positions of two shoot developmental stages

发育时期 Developmental stage	与顶端距离 Distance from tip/cm	外凸或珠状结构密度 Protrusion density/ [个?(200 μm)^-1]	乳管桥密度 Laticifer bridge density/[个?(200 μm)^-1]
古铜期	0	1.1±0.8^a	0
	7	2.2±1.1^b	0
	14	3.9±1.3^c	1.4±0.7^a
稳定期	0	4.8±1.3^d	2.7±1.2^b
稳定期	7	4.3±1.1^dc	3.2±1.1^c

Fig. 3 Observation of nuclei in carbol fuchsin stained primary laticifers in rubber tree shoots Red arrows indicate nuclei. Bars=40 μm

Fig. 4 The underlying development model of non-articulated and anastomosing laticifer

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