Storage of Cocoa (Theobroma Cacao L.) Seeds and Changes Associated With Their Deterioration

Cocoa (Theobroma cacao L .) seeds are recalcitrant and rapidly lose their viability during preparation and within two to three weeks of storage. To improve their storability, the responses of a cultivar of cocoa seeds (NA 33) to different drying methods and storage factors including seed moisture, storage temperature and fungi were investigated. Physiological, biochemical and structural changes associated with seed death caused by dehydration in the air-conditioned room (22oC, 55% RH) and chilling at 100C were also monitored

The Effects of After-ripening, Heat and Nitric Acid on Seed Dormancy of Four Local Cultivars of Padi (Oryza sativa L.)

Four local cultivars of padi, namely MR 71, MR 73, MR 77 and IR 42, have more than 80% dormant seeds when freshly harvested. After-npening, especially in the air-conditioned room was effective in overcoming their dormancy and increasing germination to more than 80% and 90% after eight and sixteen weeks respectively. Heat and nitric acid treatments were less effective than afternpening. Except for MR 71 where dormancy was less severe, germination of only 78%, 72% and 69% was 0 btained for MR 77, MR 73 and IR 42 respectively with the best heat or nitric acid treatments. Exposure to 45°C for four days was best. The effect of nitric acid van'es between van'eties. For MR 71 and MR 73, soaking for 6 -12 hours in 0.3 M nitric acid was optimal. For MR 77 and IR 42, soak"" in 0.5 M nitric acid for 3 - 6 hours and 12 hours respectively was best. The practical implications of \ the study are discusse

Effects of Dehydration on Freezing Characteristics and Survival in Liquid Nitrogen of Three Recalcitrant Seeds

The recalcitrant seeds rambutan( Nephelium lappaceum). durian (Durio zibethinus) and cempedak (Artocarpus inleger) have a high critical moisture content (below which ·rapid loss of viability occurs of 27.0%, 26.0% and 37.9%,respectively. The critical moisture for embroys were higher at 39.0% for rambutan, 53.9% for durian and 43.2% for Cempedak. Differential Thermal analysis of the embroyos confirmed that their threshhold moistures (below which there is no freezable water) were lower than their critical moistureS. The Threshhold moistures for rambutan, durian and cempedak embryos were approximately 30%, 32% and 33% respectively. It is suggested that unsuccessful attempts at cryopreservation of embroyos of 'recalcitrant seeds in the past maybe due to the absence of safe window between the high critical moisture content and the threshhold moisture. This results in freezing injury at the higher moistures and dehydration injury' at the lower moistures. Potential techniques to overcome this and improve cryopreservation of recalcitrant seed embryos are discussed

Desiccation and Cryopreservation of Embryonic Axes of Hevea brasiliensis Muell. - Arg.

Hevea embryonic axes were desiccated for a period of 1 - 5 hours and the moisture content was determined at the end of each hour of desiccation. Another set of embryonic axes were aseptically desiccated for the same period before they were cryopreserved for 16 hours by direct immersion in liquid nitrogen (-196°C). At a moisture content between 14 - 20% (desiccation for 2 - 5 hours), 20 - 69% of the embryonic axes survived cryopreservation and formed seedlings with normal roots and shoots when cultured in vitro. A bnormalities were deteched in some seedlings however, hence, refinement of the technique is needed

Some aspects of seed infection and control of the collar-rot complex of peas (Pisum sativum L.), caused by Mycosphaerella pinodes (Berk. and Blox.) Vestergr., Phoma Medicaginis var. pinodella (Jones) Boerema and Ascochyta pisi Lib. : a thesis presented in partial fulfilment of the requirements for the degree of Masterate of Agricultural Science.

The green pea, Pisum sativum L., is one of the principal field crops in New Zealand (Anon, 1970a), and essentially two varieties, P. sativum var. sativum (garden peas) and P. sativum var. arvense (field peas) are grown. Peas of the garden variety are used for human consumption and may be consumed fresh, processed or marketed as split peas. The field variety is mainly used for animal consumption. However both varieties are widely grown for seed production and are important to New zealand in international seed trade. The cultivation of green peas in New Zealand has increased steadily over the last few years. In 1966-67 approximately 28,000 acres were sown, while in 1968-69 this had increased to approximately 50,000 acres (Anon, 1970a). The main pea producing areas are Canterbury, Wellington, Marlborough, Hawkes Bay and Otago, with Canterbury alone being responsible in 1967-68 for three-quarters of the total production in New Zealand (Anon, 1969). In 1968-69 export of seed peas and artificially dehydrated peas alone resulted in total earnings of more than two million dollars (Anon, 1970b). [From Introduction

The storage of oil palm (Elaeis guineensis ) seed after high temperature treatment

For rapid and maximal germination, the oil palm seed has to undergo a high temperature treatment. After the heat-treatment the seeds, if not germinated immediately, may be stored. The conditions an-d duration of storage have not been defined and were investigated in two experiments. The results show that '[iura' type seed after heat treatment can be stored at an initial 18% moisture content in an enclosed polythene bag. The duration of storage varied with the temperature. At 20°C and 28°C the seeds could be stored for 19 and 24 weeks respectively. At 30°C germination was impaired after ten weeks of storage. A rapid loss in seed moisture was recorded at the two higher temperatures. The low temperature of SoC caused an early decline in see? viability