Effects of Temperature and Humidity Conditions during Storage on Pollen Germination of Salak (Salacca wallichiana C. Mart.)

Abstract

Hand pollination of salak is increasing in Thailand. To determine the favorable conditions for pollen collection, salak pollen was exposed to various temperature and humidity conditions. The germination percentage of fresh pollen exposed to humid conditions (90% relative humidity [RH]) varied little at temperatures ranging from 21 to 36°C for the initial 6 h following anthesis. Under dry conditions (10% RH), germinability quickly decreased, and the decrease was more remarkable at higher temperatures. To determine favorable storage conditions, pollen was stored under various temperature and humidity conditions. When pollen exhibiting 50% pre-storage germination was stored at room temperature (30°C), germination was suppressed within 7 days, regardless of humidity. When stored in a refrigerator at 5°C, the germination was ≈40% for 7 days at 63% RH. The germination remained the proper percentage of >20% after 14 to 60 days of storage at 36% RH. Germination was also >20% when stored in a freezer at −40°C for 360 days and thawed at 25°C with 60% RH. Germination decreased to <20% within 90 days of storage when stored at both −40°C or −20°C and then thawed under dry conditions (20–40% RH). Avoidance of hot and dry conditions was found to be necessary for the salak pollen. A temperature of 5°C at 60% RH was favorable for several days of storage, and 5°C at 35% RH was favorable for several weeks of storage. For several months to up to one year of storage, −40°C followed by thawing at 25°C at 60% RH is recommended.