Physiological Quality and Desiccation Sensitivity of Rubber (Hevea brasiliensis) Seeds during Fruit Maturation

Abstract

The physiological quality and desiccation of rubber seeds were investigated during development. Fruits of rubber clone RRIM 600 at different stages of development were collected from a plantation in Nakhon Sri Thammarat province, southern Thailand, during July–August 2012. Seeds of deep green fruit, yellowish-green fruit, brown fruit and from the naturally shedding stage were tested for their weight, moisture content, germination, mean germination time, seedling shoot height, seedling shoot dry weight, electrical conductivity and desiccation tolerance during dry storage. Rubber seeds with high germination ranging from 86.67 to 95.00% were obtained from the yellowish-green fruit, brown fruit and naturally shedding stages. However, the seeds reached physiological maturity at the brown fruit stage with values for seed dry weight, moisture content and germination of 2.93 g per seed, 34.54% and 95.00%, respectively. At the shedding stage, the seeds had a moisture content and a high germination of 22.17% and 91.66%, respectively. The critical moisture content of the seeds was 15% and at this level, they were very short lived (3–7 d in dry conditions). The seeds with a moisture content of about 15% and from 11 to 12% had germination of 58.33–63.34% and 1.67–8.34%, respectively. Therefore, the early collection of the shed seed is recommended to ensure high quality seed is obtained. Such information may be helpful for improving the seed collection or transport procedures and ensuring high seed performance in the seedbed for successful rootstock production.