OCR Text |
Show I Bees Are Factors In Alfalfa Seed Production Remembering that tripping is essential es-sential for pod development Pollination Poll-ination and Fertilization; Pollination Pollin-ation is actually the transfer of pollen from the Anthers ( male part ) to the Stigma (female part). If pollen from another alfalfa plant (known as "foreign pollen") comes in contact with the stigma, both the flower's own pollen and the foreign pollen wil germinate, but the germ tubes from the foreign for-eign pollen usually get to the ovule ov-ule first, producing cross-fertilized seed. If no foreign pollen is present tnppmg can be induced by excessive excess-ive heat and is favored by low humidity. The question: To What extent does tripping occur spontaneously spon-taneously in nature? This cannot be accurately answered. However, it is certain that some spontaneous spontan-eous tripping does occur. A few Plants in a population will trip automatically; some are difficult to trip. The population varies between be-tween these two limits - - it is believed that the percent of the population exhibiting self-tripping will be proportional to the environmental envir-onmental conditions especially tern perature and humidity. Unfortunately, spontaneous tripping trip-ping is subject to the limitations of self-pollination and so is actually actu-ally a detriment to the crop. Furthermore, Fur-thermore, temperatures high enough en-ough to case appreciable spontaneous spontan-eous tripping would probably be injurious to the plant under field conditions. Even slight wilting, cau ses many flowers to drop. Nevertheless, Never-theless, these weather conditions are important in their effect on insect activity and its benefits. In factory a machine used for mechanical mech-anical tripping would have to cover cov-er the field several times durng flowerng without excessive damage dam-age to the plants and at the same time trip and cross-pollinate a high percentage of the flowers. This appears ap-pears to be an engineering impossibility. imposs-ibility. Material taken from Circular No. 125 of Ut. Ag. Experiment Station at Logan. "Tripping and Cross-Pollination by Insects'" to be discussed next week. the first place, bees fly best when the weather is dry and warm. In the second place, since the percent age of flowers tripped by nectar-collecting nectar-collecting honey bees is variable, it would seem logical to suppose that their efficiency would be gVea ter under the warm, dry conditions which favor automatic tripping 4. HUMIDITY: Weather conditions con-ditions of the West are generally more favorabe for alfalfa seed production than are those of the Midwest, East or South. Conditions associated with the lower rainfall self-fertilization ( fertilization with the flower's own pollen) will result re-sult to a limited extent. Only 36.6 percent of the self-pollinated (or "selfed" flowers on the average formed pods compared to 60 percent per-cent of the crossed flowers. Cross-pollination Cross-pollination also increases the num ber of seeds per pod. The percent of flowers forming seed pods when they are all tripped trip-ped and crossed 47 to 78 percent') may be considered the upper limit of the plant's ability to profit from pollination. Under natural conditions condit-ions an average of only 27 percent of the flowers form seed pods. Since Sin-ce most of the flowers tripped under un-der natural conditions are cross-pollinated, cross-pollinated, this low percentage appears ap-pears to result from failure of many of the flowers to be tripped. It is then obvious that Alfalfa Must be Tripped and Cross Pollinated Pollin-ated in order to set an appreciable amount of seed. Methods of Obtaining Pollination Methods used in obtaining pollination poll-ination incude - Wind, Rain, Heat, and Humidity, also Mechanical Tripping and tripping and crOss-polination crOss-polination by insects. 1. WIND: Investigators have concluded that wind plays a minor min-or role in tripping. Limited tripping trip-ping will occur if the plants are whipped against each other or in the ground. The drying effect of the wind may also contribute to conditions favorable for automatic tripping. However, since Alfalfa pol len is not adapted to air transportation trans-portation and the flowers are not adapted to receive pollen from the air, it is inconceivable that tripping caused by wind could result re-sult in much cross-pollination. 2. RAIN: Raid trips some flowers flow-ers but the subsequent pod set, is low. An average of 8.3 percent tripping by rain was observed by investigators. 3. HEAT & HUMIDITY: Under laboratory conditions automatic turn numiciuy or tne West are: (1) More days of good flying weather for bees, (2) Increased nectar flow during clear weather. (3) Theoretically Theoret-ically greater likelihood of tripping trip-ping by nectar-collecting bees. 5. MECHANICAL TRIPPING: No method of tripping flowers mechanically mech-anically with resulting increase of seed has been devised and experimentally exper-imentally tested. Eleven methods were tested by Silversides and Olson, Ol-son, such as harrowing and pulling a wire over the plants, this type of tripping not only damages the plants, but is also subject to the limitations of selfing. To be satis- |