Bark Structure of the Clone ‘RY7-33-97’ with Different Level of Tapping Panel Dryness (TPD) in Rubber Tree (Hevea brasiliensis Muell. Arg.)

doi:10.3969/j.issn.1000-2561.2021.07.014

Abstract

Abstract:

Natural rubber is extracted from latex that collected from the bark of rubber trees by tapping. The structure of bark plays an important role in the production of natural rubber. Tapping panel dryness (TPD) is one of the key factors to affect yield of rubber trees, but the mechanism of TPD was still less known and the change of bark structure of TPD was rarely studied. By using the optical microscopy technology, the morphological structure and location of laticifer, sieve tube, tannin cell and stone cell in the bark of ‘RY7-33-97’ with different level of TPD were studied. Compared to the healthy rubber tree, the bark structure in the third and the fifth grade of TPD tree changed obviously. Accompanying the increase of TPD extent, the number of laticifer lines was difficult to be counted for the disordered arrangement. The swell laticifer appeared gradually inward to cambium from sandy skin. Besides the abnormal swelling and light dying, hollow laticifer also was observed. The diameter of swell laticifer was up to 40 µm, but the effective laticifer usually was short of 20 µm and even smaller when TPD aggravated. The diameter of sieve tube decreased obviously under the condition of non-latex flow. Stone cells formed largely in the yellow skin and even went deeply into the water sac skin and the cambium in TPD rubber tree. The number of tannin cells increased obviously when TPD happened, especially in the tender tissue such as water sac skin. This study would lay a foundation for illuminating the mechanism of TPD and provide a theoretical basis for developing the prevention technology of TPD in rubber trees.

Key words: Hevea brasiliensis Muell. Arg., tapping panel dryness (TPD), bark structure, laticifer, tannin

CLC Number:

S794.1

LU Yali, ZHANG Shixin, WANG Zhenhui, TIAN Weimin, SHI Minjing. Bark Structure of the Clone ‘RY7-33-97’ with Different Level of Tapping Panel Dryness (TPD) in Rubber Tree (Hevea brasiliensis Muell. Arg.)[J]. Chinese Journal of Tropical Crops, 2021, 42(7): 1918-1924.

Figures/Tables 4

Fig. 1 Bark structure of health tree and different grades of TPD tree in ‘RY7-33-97’ A: Cross-section of the healthy bark; B-D: Cross-section of the normal latex flow, punctiform latex flow and non-latex flow of bark in the third grade TPD; E-F: Cross-section of punctiform latex flow and non-latex flow of bark in the fifth grade TPD tree. The white arrows show the stone cells; The red arrows show swelling laticifers; Ca: Cambia; Scale bars=200 µm.

Fig. 2 Analysis of parameters about the laticifer and sieve tube of bark in health tree and different grades of TPD tree in ‘RY7-33-97’ * means significant difference at the 0.05 level; ** means extremely significant difference at the 0.01 level.

Fig. 3 Accumulation of tannin in bark of healthy trees and different grades of TPD trees in ‘RY7-33-97’ A1-A2, B1-B2, C1-C2, D1-D2, E1-E2, F1-F2: Cross-section of the bark, showing that the inside next to the cambia and the outside next to the sandy layer of different samples for the healthy tree, the places of normal latex flow, punctiform latex flow and non-latex flow of the third grade TPD, the places of punctiform latex flow and non-latex flow of the fifth grade TPD respectively. The red arrow shows the tannin cell; Ca: Cambia; Scale bars=100 µm.

Fig. 4 Fluorescence localization of tannin in bark of healthy trees and different grades of TPD trees in ‘RY7-33-97’ A1-F1: Fluorescence localization of tannin cell in barks, A1 is the bark of healthy tree, B1-D1 is the bark for the normal latex flow, punctiform latex flow and non-latex flow in the third grade TPD respectively, E1, F1 is the bark for punctiform latex flow and non- latex flow in the fifth grade TPD tree respectively; A2-F2 is merge images, corresponding to the left images. The red arrows show the tannin cells. Scale bars = 100 μm.

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