Passion Fruit: Optimum Growth Areas - Criterion 4: In total, there should be < 25 days per annum with frost

Passion fruit are believed to have originated from southern Brazil (Kenyaweb, 2005).The most commonly commercially grown of 55 edible species of passion fruit is Passiflora edulis, which consists of perennial woody vines with each producing about 100 fruits per year (RBGK, 2005). In South Africa passion fruit ideally requires a cool subtropical climate for optimum production (Smith, 1998). The vines prefer moderate temperatures throughout the year, with monthly means of daily maxima < 29 degree Celsius. The plants are sensitive to severe frosts, and monthly means of minimum temperatures should be > 6 degree Celsius (NDA, 2005). For commercial production under rainfed conditions MAP should ideally exceed 1 200 mm and be well distributed throughout the year (NDA, 2005), as it is important to maintain the soil moist throughout the growing season to keep the vines flowering and fruiting for longer periods and prevent the fruit from shriveling and falling prematurely (Kenyaweb, 2005). Total commercial production of passion fruit in South Africa is 1 300t per season, with a range (between 1998/9 - 2003/4) in more recent from 900 - 1 700 t (NDA, 2005).The gross value is R65 million/year (NDA, 2005). Criteria for climatically optimum growth areas for passion fruit were refined by Bower (2005). Six criteria were identified and using the 1` x 1` gridded information on temperature related parameters derived by Schulze and Maharaj (2004), the following criteria were mapped: Criterion 1: > 330 days per year with a minimum temperature exceeding 2 degree Celsius; Criterion 2: Fewer than 2 consecutive days per annum with minimum temperatures < -2 degree Celsius; Criterion 3: There should not be > 3 consecutive frost days per annum; Criterion 4: In total, there should be < 25 days per annum with frost; Criterion 5: Maximum temperatures should be < 28 degree Celsius on at least 25 days of each month; Criterion 6: Maximum temperatures should not exceed 35 degree Celsius on any two consecutive days per month. Mapped criteria were given either categorical or probabilistic weightings and when the six maps were superimposed, suitable and less suitable climatically optimum growth areas could be identified. The assumption was made that for commercial production the passion

百香果一般认为起源于巴西南部（Kenyaweb，2005）。在55个可食用西番莲属物种中，商业化种植最为广泛的是紫果西番莲（Passiflora edulis），该物种为多年生木质藤本，单株年结果量约100个（RBGK，2005）。在南非，百香果的最优生产需要凉爽的亚热带气候（Smith，1998）。该藤本全年偏好温和气温，月均日最高温需低于29摄氏度。植株对重度霜冻较为敏感，月均最低温应高于6摄氏度（NDA，2005）。在雨养农业条件下开展商业化种植时，年平均降水量（Mean Annual Precipitation，MAP）理想值应超过1200毫米，且全年降水分布需均匀（NDA，2005）——这是因为在整个生长季维持土壤湿润，可延长藤本的开花结果时长，并防止果实皱缩与提前脱落（Kenyaweb，2005）。南非百香果年度商业总产量为1300吨/种植季，1998/99至2003/04年间的年产量波动区间为900至1700吨（NDA，2005），年产值达6500万兰特/年（NDA，2005）。鲍尔（Bower，2005）对百香果气候最优种植区的判定标准进行了优化。研究共确定6项判定标准，并结合舒尔茨与马哈拉杰（Schulze and Maharaj，2004）基于1'×1'网格得到的气温相关参数数据，对以下标准进行了空间制图：标准1：全年最低温高于2摄氏度的天数不少于330天；标准2：全年连续最低温低于-2摄氏度的天数不超过2天；标准3：全年连续霜冻天数不得超过3天；标准4：全年总霜冻天数应少于25天；标准5：每月至少有25天的日最高温低于28摄氏度；标准6：每月内任意连续两日的日最高温均不得超过35摄氏度。对各制图标准赋予分类权重或概率权重后，将6幅专题图叠加，即可识别出气候适宜与较适宜的最优种植区。研究假设，若用于商业化种植，百香果